JP2006336067A - Method for manufacturing non-heat treated high-strength bolt - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily improve the relaxation characteristic of a non-heat treated high-strength bolt. <P>SOLUTION: After a non-heat treated bolt is formed (S10), the axial load equivalent to ≥80% and <100% of the tensile strength of the bolt is applied to the bolt to provide the plastic strain by using a tensile tool (S12), and the bolt is unloaded and detached from the tool (S14). The detached bolt is subjected to the bluing treatment in the treatment condition range surrounded by each treatment condition of 5 minutes at 200°C, 60 minutes at 200°C, 1 minute at 250°C, 10 minutes at 250°C, 0.5 minute at 300°C, 5 minutes at 300°C, 0.5 minute at 400°C, and 1 minute at 400°C in the relationship between the temperature and the time for heat treatment (S16). According to the load application condition, the bluing treatment can be performed before applying the load, and the bluing treatment can be eliminated. The load can be applied by using a rotating and fastening tool in place of the tensile tool. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a non-tempered high-strength bolt, and more particularly to a method for manufacturing a non-tempered high-strength bolt excellent in relaxation characteristics.

  Common high-strength bolt steels are medium carbon alloy steels such as SCM435, SCM440, and SCr440, and the necessary strength is ensured by quenching and tempering (tempering). Is called tempered bolt. However, it is known that in general high-strength bolts used for automobiles and various industrial machines, when the tensile strength exceeds about 1200 MPa, the sensitivity of so-called delayed fracture increases.

  There are two types of delayed fractures, one occurring in a non-corrosive environment and the other occurring in a corrosive environment. The generation factors are said to be intricately intertwined, and it is difficult to generally identify the cause. Although factors such as tempering temperature, structure, material hardness, crystal grain size, and various alloying elements have been recognized as factors that influence delayed fracture, effective means for preventing delayed fracture have been established. In fact, various methods have been proposed by trial and error.

  In particular, in a bolt used at a high temperature, a so-called relaxation phenomenon (stress relaxation) that causes a decrease in tightening force during use becomes significant. For example, when left standing at 150 ° C., the load may be reduced by 30%. Thus, in the environment where high-strength bolts are used, delayed fracture and relaxation phenomenon are known as problems.

  In Patent Document 1, a steel material having a pearlite structure of 80% or more is strongly drawn by a patenting treatment (pearlite treatment), and is formed into a bolt shape by cold rolling. ) To improve delayed fracture characteristics and relaxation characteristics.

  Patent Document 2 points out that as a cause of the relaxation phenomenon, many dislocations are introduced into the crystal lattice of a steel bolt because it undergoes plastic working such as drawing in the manufacturing process. That is, it is stated that, under tensile stress such as tightening of bolts, these dislocations move and cause elongation, and stress relaxation occurs due to the elongation. And it touches on the blueing process of the steel volt | bolt of patent document 1, and this process method still says that the improvement of a relaxation characteristic is not enough. Then, the relaxation characteristics can be improved by screwing the bolt into the bolt holder, applying a tensile stress in the axial direction exceeding the elastic limit, and performing a heat treatment between 200 ° C. and 300 ° C. in the loaded region. It is disclosed.

JP 2001-348618 A JP 2004-116624 A

  In the method according to the embodiment of Patent Document 2, a bolt is screwed into a bolt holder and an axial tensile stress exceeding the elastic limit is applied, and heat treatment between 200 ° C. and 300 ° C. is performed in that state. That is, since each bolt is attached to the bolt holder and put into the heat treatment apparatus, the heat treatment apparatus becomes large and the productivity is not good. However, Patent Document 2 states that the mere bluing heat treatment disclosed in Patent Document 1 is not enough to improve the relaxation characteristics. Thus, in the prior art, there remains a problem with respect to improving the relaxation characteristics of the non-tempered high strength bolt.

  The objective of this invention is providing the manufacturing method of the non-tempered high strength bolt which makes it possible to improve the relaxation characteristic in a non-tempered high strength bolt more easily.

  The manufacturing method of the non-tempered high-strength bolt according to the present invention is based on the facts found in the experiment for improving the relaxation characteristics, which is the manufacturing method. The experiment includes a method other than heat treatment while applying an axial load and applying plastic strain, and more specifically, unloading the load after applying plastic strain to improve relaxation characteristics. This was done for the purpose of not being able to plan. As a result, it has been found that the relaxation characteristics of high-strength bolts can be improved even when unloading after applying plastic strain under some conditions. In the following, these experimental results are used as a method for producing a non-tempered high strength bolt.

  The method for producing a non-tempered high strength bolt according to the present invention is a method for producing an axial load corresponding to 80% or more and less than 100% of the tensile strength of the bolt after forming the non-tempered bolt. In the relationship between the load loading process for applying plastic strain by loading, the unloading process for gradually unloading and removing the bolt from the jig, and the temperature and time for heat treatment of the removed bolt, 5 minutes at 200 ° C. and 200 ° C. 60 minutes at 250 ° C and 1 minute at 250 ° C and 10 minutes at 250 ° C and 0.5 minutes at 300 ° C and 5 minutes at 300 ° C and 0.5 minutes at 400 ° C and 1 minute at 400 ° C And a processing step of performing blueing processing within a processing condition range surrounded by each processing condition.

  With this configuration, the bolt is unloaded after the load loading step using a tension jig, and the removed bolt is heat-treated under a predetermined processing condition range, so it is not necessary to heat-treat with the load applied. The relaxation characteristics of the non-tempered high strength bolt can be improved more easily.

  Moreover, the manufacturing method of the non-tempered high-strength bolt according to the present invention is the axial direction corresponding to 90% or more and less than 100% of the tensile strength of the bolt using an arbitrary tensile jig after forming the non-tempered bolt. It includes a load loading step of applying a load and applying plastic strain, and an unloading step of gradually unloading and removing the bolt from the tension jig.

  According to this configuration, if the load is strong within a predetermined range, it is only necessary to unload the bolt after the load loading process using a tension jig. Improvements can be made even more easily.

  Moreover, the manufacturing method of the non-tempered high-strength bolt which concerns on this invention is the blueing process of processing temperature range 200 degreeC or more and 250 degrees C or less and processing time range 15 minutes or more and 30 minutes or less after shaping | molding a non-tempered bolt. And a load load that gives plastic strain by applying an axial load corresponding to 90% or more and less than 100% of the tensile strength of the bolt using an arbitrary tensile jig. And a unloading step of gradually unloading and removing the bolt from the tension jig.

  According to this configuration, if the load is strong within a predetermined range, heat treatment is performed in advance, and then the bolt is loaded and unloaded using a tension jig. The relaxation characteristics of the bolt can be improved more easily.

  Moreover, in the manufacturing method of the non-tempered high-strength bolt according to the present invention, the tension jig is shorter than the effective length L1 of the threaded portion of the bolt after molding, and the bolt is used to be fitted to the counterpart in actual use. It has a shape in which a screw portion of a bolt is fitted to at least a part of an arbitrary length L3 that is longer than the fitting length L2, and the load portion of the load loading step includes a bolt jig portion that applies plastic strain. A step of fitting at least a part of the portion of the length L3 and attaching the bolt to the tension jig, and a tension step of pulling the bolt attached to the tension jig in the axial direction under an arbitrary axial load It is preferable to have.

  With the above-described configuration, plastic strain can be applied to a screw portion that is not fitted in the effective length L1 of the screw portion using a tension jig.

  The non-heat treated high-strength bolt manufacturing method according to the present invention is a method of forming a non-heat treated bolt and then tightening the bolt with an arbitrary snag torque using an arbitrary rotary tightening jig. 5 minutes at 200 ° C. in the relationship between the load loading step of retightening at an angle of less than an angle, the unloading step of unloading and removing the bolt from the jig, and the temperature and time for heat treatment of the removed bolt, and 60 minutes at 200 ° C and 1 minute at 250 ° C and 10 minutes at 250 ° C and 0.5 minutes at 300 ° C and 5 minutes at 300 ° C and 0.5 minutes at 400 ° C and 1 at 400 ° C And a processing step of performing a blueing process within a processing condition range surrounded by each processing condition.

  With this configuration, the bolt is unloaded after the load loading process using the rotary tightening jig, and the removed bolt is heat treated under a predetermined processing condition range. In other words, the relaxation characteristics of the non-tempered high strength bolt can be improved more easily.

  The non-heat treated high-strength bolt manufacturing method according to the present invention is a method of forming a non-heat treated bolt, and then tightening the bolt with an arbitrary snag torque using an arbitrary rotary tightening jig. It includes a load loading step of performing additional tightening at an angle of less than or equal to a degree, and an unloading step of gradually unloading and removing the bolt from the rotary tightening jig.

  According to this configuration, if the load is strong within a predetermined range, it is only necessary to unload the bolt after the load loading process using the rotary tightening jig, and the relaxation in the non-tempered high strength bolt Improvements in properties can be made even more easily.

  Moreover, the manufacturing method of the non-tempered high-strength bolt which concerns on this invention is the blueing process of processing temperature range 200 degreeC or more and 250 degrees C or less and processing time range 15 minutes or more and 30 minutes or less after shaping | molding a non-tempered bolt. And the non-tempered bolt after the brewing treatment is tightened with an arbitrary snag torque of the bolt using an arbitrary rotary tightening jig, and further tightened at an angle of 90 degrees to 270 degrees And a load unloading step of unloading and removing the bolt from the rotary fastening jig.

  According to this configuration, if the load is strong within a predetermined range, heat treatment is performed in advance, and then the bolt is loaded and unloaded using a rotary tightening jig. The relaxation characteristics of the high-strength bolt can be improved more easily.

  Further, in the method for producing a non-tempered high strength bolt according to the present invention, the high strength bolt is a bolt with a head having a head having a diameter larger than the shaft diameter, and the rotary fastening jig is a screw portion of the bolt. Including a through-hole having a part of a screw portion of an arbitrary length L3 that is shorter than the effective length L1 and whose bolt is fitted to the other party in actual use and longer than the fitting length L2. When the bolt is inserted into the through hole, screwed into the threaded portion, and fitted with the length of L3, the head has a shape that stops at the end of the through hole. Screwing in until it stops at the end of the rotary tightening jig, and the bolt with the head with a snug torque of any size with the head stopped at the end of the rotary tightening jig Tightening process of tightening and tightening bolts with heads with snag torque It is preferred to have the tightening step of tightening in addition any angle al, the.

  With the above-described configuration, by tightening the head-attached bolt using the rotary fastening jig, plastic strain can be applied to the screw portion that is not fitted in the effective length L1 of the screw portion.

  In the method for producing a non-tempered high-strength bolt according to the present invention, the high-strength bolt is a stud bolt having screw portions at least at both ends of the shaft, and the rotary tightening jig is an effective screw portion of the bolt. Including a hole that has a screw part of an arbitrary length L3 that is shorter than the length L1 and that is longer than the use fitting length L2 that the bolt is fitted to the other party in actual use, and inserts a stud bolt into the hole When the screw part is screwed into the screw part and the screw part at one end thereof is fitted with the length of L3, the other end of the stud bolt has a shape protruding more than L2 from the end part of the hole. Installation process of inserting into the hole of the rotary tightening jig, screwing it into the screw part, fitting the screw part at one end to the length of L3, and attaching the tightening nut to the other end of the stud bolt protruding from the end of the hole And tighten the clamping nut And then tightening the stud bolt with a snug torque of any size, and a retightening step of further tightening the tightening nut at an arbitrary angle from the tightened state of the snag torque. Is preferred.

  With the above-described configuration, the strain bolt can be plastically strained on the screw portion that is not fitted in the effective length L1 of the screw portion by tightening the stud bolt using the rotary fastening jig.

  As described above, according to the method for producing a non-tempered high-strength bolt according to the present invention, the relaxation characteristics can be improved more easily.

  Embodiments according to the present invention will be described below in detail with reference to the drawings. In the following, a method for manufacturing a non-tempered high-strength bolt in which six types of relaxation characteristics are improved will be described. However, in common with them, the relaxation characteristics are improved by a manufacturing method that does not require heat treatment with a load applied. There is. In these six manufacturing methods, there are three load methods, one using a tension jig and the other using a rotary tightening jig. That is, it can be divided into three different manufacturing methods except for differences in load-loading jigs.

  The difference in processing among the three manufacturing methods is caused by the degree of load, that is, the magnitude of plastic strain applied to the bolt after forming. That is, the first manufacturing method is performed by the procedure of load loading-unloading-heat treatment. In the second and third manufacturing methods, the degree of load is made stronger than in the first manufacturing method, and in the second manufacturing method, only load load-unloading is required. In the third method, heat treatment is performed in advance, and thereafter, only loading / unloading is required. Hereinafter, these six production methods will be described in detail.

  FIG. 1 is a flowchart showing a processing procedure of a method for manufacturing a non-tempered high strength bolt. The manufacturing method of the high-strength bolt is to improve the relaxation characteristics by performing a predetermined treatment on the formed bolt, that is, the one already formed into the outer shape of the bolt. This is a method for manufacturing a bolt having an outer shape and excellent relaxation characteristics on the premise of manufacturing.

  The bolt forming step (S10) is a step until a material having a bolt outer shape is produced from a material. The contents are: a process for preparing a piano wire material, a patenting process for the material, that is, a process for performing a pearlite process so as to obtain an arbitrarily determined pearlite occupancy ratio, and a surface reduction rate that is arbitrarily determined for the pearlite process. That is, it includes a processing step of drawing under a reduction rate of the cross-sectional area of the wire. After this step, it is preferable to determine the material material, the patenting process, the conditions for the drawing process, and the like so that the tensile strength is 1500 MPa to 1700 MPa. After the drawing process, under the optional rolling conditions, the stud bolts are only rolled, and the head bolts are further molded.

  As a material of the piano wire, SWRS82B defined by JIS can be used. Of course, a raw material wire made of other materials, for example, a carbon steel wire SWRCH for cold forging may be used. The wire diameter can be set to 8 mm to 9.5 mm in consideration of the area reduction rate and the bolt size in the drawing process.

  As the patenting treatment, the wire material having a pearlite structure can be obtained by heating to 950 ° C. to form austenite and then performing a constant temperature transformation treatment in a 525 ° C. lead bath. Of course, these processing temperature conditions may be changed according to the material.

  In the drawing process, after a patenting process, a known pickling process, a bond process, and the like are performed, and the sheet is processed with an arbitrary reduction in area by a drawing apparatus. The area reduction rate is about 50% in order to ensure the tensile strength. The wire diameter after the surface reduction is 5.35 mm or 6.35 mm, and as a result, the bolt after rolling is M6 with an effective diameter of 5.35 mm or an M7 stud bolt with an effective diameter of 6.35 mm and a hexagon head bolt. And Here, a stud bolt is a bolt without a head larger than a shaft diameter. Further, the M6 bolt having an effective diameter of 5.35 mm is a bolt having the same diameter as that of the shaft without the screw portion and the effective diameter of the screw portion of 5.35 mm. The effective diameter is an intermediate diameter between the crest diameter and the trough diameter of the screw portion. In addition, what is used corresponding to the effective diameter is a nominal diameter. In this case, the diameter of the shaft without the screw portion is the same as the crest diameter (nominal diameter) of the screw portion. The effective diameter shape and the nominal diameter shape may differ in the thread forming distortion in the bolt forging process and the plastic strain of the axial load load described later, and thereby, the manufacturing method of the non-tempered high strength bolt Conditions may vary.

  Thus, if bolt formation is made, it will become a load loading process (S12) which next gives plastic strain with a tension jig. The load loading step is a step of pulling the bolt beyond its elastic limit and giving an arbitrary plastic strain to the screw portion. It is preferable that the plastic strain is applied to a portion that is not a so-called fitting portion that fits with the other screw portion when the bolt is attached to an actual device or the like. This plastic strain is introduced in order to suppress the phenomenon of relaxation (stress relaxation) due to proliferation of movable dislocations introduced in the process up to bolt forming. Therefore, this plastic strain is preferably applied to a portion where the bolt is extended when fastening the bolt, that is, a screw portion which is not a fitting portion.

  This will be described with reference to FIG. FIG. 2A is a view showing a so-called stud bolt 10 in which screw portions 12 are cut at both ends of the shaft portion with an effective length L1. Here, L2 is a length that the stud bolt 10 is fitted to the mating female screw in actual use, that is, a so-called use fitting portion 14. Therefore, it is preferable that plastic strain is generated in a portion other than the use fitting portion 14 in the screw portion 12, that is, in the bare screw portion 15 in use when not being fitted to the mating female screw in actual use.

  FIG. 2B shows a so-called hexagon bolt 20, in which a threaded portion 22 is cut at an effective length L <b> 1 on the distal end side of the shaft portion, leaving the neck portion below the head portion 21. Here, L2 indicates the use fitting length of the use fitting portion 24 in which the hexagon bolt 20 is fitted with the mating female screw in actual use. Therefore, it is preferable that plastic strain is generated in the bare screw portion 25 in use other than the use fitting portion 24 in the screw portion 22.

  FIG. 3 is a view for explaining the structure and operation of a tension jig for applying plastic strain to the bare screw portion other than the bolt use fitting portion. Elements similar to those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted. FIG. 3A shows a stud bolt tension jig 30 for imparting plastic strain to the stud bolt 10. The stud bolt tension jig 30 is a member in which a female screw portion 18 having an opening on one side is cut, and is a kind of so-called cap nut. The effective length of the female screw portion 18 is indicated by L3. The length of L3 is set shorter than the effective length L1 of the stud bolt 10 and longer than the use fitting length L2. Two such stud bolt tensioning jigs 30 are prepared for one stud bolt 10, and the threaded portions 12 at both ends of the stud bolt 10 are fitted into each of the female threaded portions 18. In this state, the length of the bare screw portion 16 in this case is L4 = L1−L3. This length L4 is shorter than the length L1-L2 of the bare screw part 15 demonstrated in FIG.

  With the stud bolt tension jig 30 having such a configuration attached to both ends of the stud bolt 10, each stud bolt tension jig 30 is hung on a tension device (not shown) and is shown in FIG. The upper stud bolt tension jig 30 is pulled in the + X direction shown in the figure, and the lower stud bolt tension jig 30 is pulled in the -X direction. As a result, when the axial load is applied to the stud bolt 10 and the load load exceeds the elastic limit of the material of the stud bolt 10, the tensile jig 30 for both stud bolts is removed after the load is removed. Plastic strain occurs in the area between. Here, the plastic strain in the screw portion 12 occurs at the bare screw portion 16.

  FIG. 3B shows a hexagon bolt tensioning jig 40 for applying plastic strain to the hexagon bolt 20. The hexagon bolt tension jig 40 includes a nut 42 that can be fitted to the hexagon bolt 20, an upper jig 44, and a lower jig 46. Here, the nut 42 is used whose height, that is, the length of the female screw, is shorter than the length L1 of the screw portion 22 of the hexagon bolt 20.

  The upper jig 44 is a member that cooperates with the lower jig 46 and has a function of pushing down the nut 42 fitted into the hexagon bolt 20 in the −X direction shown in FIG. The upper jig 44 has a bottom portion and a plurality of standing wall portions extending upward from the bottom portion, and the screw portion 22 of the hexagon bolt 20 can pass through the bottom portion, but the through hole has a smaller hole diameter than the outer shape of the head portion 21. A hole is provided.

  The lower jig 46 is a member having a function of pushing up the head 21 of the hexagon bolt 20 in the + X direction shown in FIG. 3B in cooperation with the upper jig 44. The lower jig 46 has a cylindrical shape, and has a through hole through which the threaded portion 22 of the hexagon bolt 20 can pass and a hole through which the wall portion of the upper jig 44 can move freely. Provided. Here, the cylindrical inner diameter of the lower jig 46 is set larger than the outer shape of the bottom of the upper jig 44.

  Then, as shown in FIG. 3B, the wall portion of the ceiling portion of the lower jig 46 is directed from the lower side of the cylindrical hole of the lower jig 46 with the wall portion of the upper jig 44 facing upward. When the wall portion is passed through the through hole, the respective arrangements are set and combined such that the through hole in the bottom portion of the upper jig 44 and the through hole in the ceiling portion of the lower jig 46 are arranged substantially coaxially. . Here, the screw portion 22 of the hexagon bolt 20 is brought from above the upper jig 44 and inserted into the through hole at the bottom thereof. Then, the tip of the screw portion 22 protruding from the through hole is further passed through the through hole in the ceiling portion of the lower jig 46, and the nut 42 is fitted to the screw portion 22 protruding beyond the tip. The nut 42 is fitted in such a manner that the bare screw portion 26 is left on the root side of the length L1 without fitting the screw portion 22 to the full base. As shown in FIG. 3B, when the nut 42 is fitted from the tip of the screw portion 22 to the length of L3, the length L4 of the bare screw portion 26 on the root side of the screw portion 22 is L1-L3. Become.

  In this state, the upper jig 44 and the lower jig 46 are respectively put on a tensioning device (not shown), and the upper jig 44 shown in FIG. 3B is placed in the −X direction shown in FIG. Pull 46 in the + X direction. As a result, the head 21 of the hexagon bolt 20 is pushed up in the + X direction and the nut 42 is pushed down in the −X direction, so that an axial load is applied to the hexagon bolt 20 and the load load is the elastic limit of the material of the hexagon bolt 20. When the size exceeds the limit, plastic strain occurs in the portion between the head 21 and the nut 42 after the load is removed. Here, the plastic strain in the screw portion 22 occurs at the bare screw portion 26.

  As described above, both the stud bolt 10 and the hexagon bolt 20 are shorter than the effective length L1 of the threaded portion of the bolt after forming as a tension jig, and the bolt is fitted to the counterpart in actual use. A bolt having a shape that fits the screw portion of the bolt at at least a part of an arbitrary length L3 longer than the fitting length L2 is used, and the screw portion of the bolt that gives plastic strain is the length of the tension jig. Fit at least part of the L3 part, attach the bolt to the tensioning jig, and pull the bolt attached to the tensioning jig in the axial direction under any axial load to make the bare screw part plastic Can be distorted.

  As the tension jig, FIG. 3 (a) has been described with a cap nut shape, but it may be a simple nut or a member having a shape that can be easily attached to a tension device, such as a plate with a female thread cut. Good. Further, in FIG. 3 (b), the structure including a pair of upper jig and lower jig has been described, but the hexagon bolt is pulled using the head of the hexagon bolt and a nut fitted into the hexagon bolt. Any member may be used, for example, a combination of a member supporting the head and a member supporting the nut, and the member supporting the nut may be a member having a female screw cut.

  The axial load for applying plastic strain can be applied in a range exceeding the elastic limit of the bolt and less than the tensile strength, but here, a load corresponding to 80% or more of the tensile strength is applied. The reason is based on the results of detailed experiments described later.

  Returning to FIG. 1 again, after a predetermined load is applied to give plastic strain, the load is unloaded (S14). Specifically, the load of the tensioning device is returned to zero, and the stud bolt and the hexagon bolt are removed from the tensioning jig described with reference to FIGS. By this unloading, plastic strain is introduced into the stud bolt and the hexagon bolt.

  Next, the removed bolt is subjected to a blueing process (S16). The bluing process is a heat treatment process called a so-called strain aging process. Here, in relation to the temperature and time for heat treatment, 5 minutes at 200 ° C., 60 minutes at 200 ° C., 1 minute at 250 ° C., 10 minutes at 250 ° C., 0.5 minutes at 300 ° C., and Heat treatment is performed in a processing condition range surrounded by processing conditions of 300 ° C. for 5 minutes, 400 ° C. for 0.5 minutes, and 400 ° C. for 1 minute. The reason for determining this processing condition range depends on the results of experiments detailed below. In the heat treatment, a plurality of bolts are collectively processed.

  Here, the experiment conducted to determine the magnitude of the load applied in S12 and the heat treatment condition range performed in S16 will be described. Here, a large number of bolts formed in S12 are prepared, the magnitude of the applied load is changed to a magnitude corresponding to 75%, 80%, and 95% of the tensile strength, and the heat treatment temperature is set to 200 ° C. The heat treatment time was changed to 0.5 minutes, 1 minute, 5 minutes, 30 minutes, and 60 minutes by changing to 250 ° C., 300 ° C., and 400 ° C. The bolts thus treated were each subjected to a tensile test, and the yield ratio = 0.2% proof stress and 0.2% proof stress, which are the stresses when the tensile strength and 0.2% elongation remain. (Yield strength / tensile strength) = (0.2% yield strength / tensile strength) was determined.

  The result is shown in FIG. Here, the test groups are divided into seven groups. Test 1 is a bolt tensile test as it is, that is, only the step of S10. Test 2 is a tensile test for a product subjected to a blueing treatment at 250 ° C. for 30 minutes after bolt formation. This condition corresponds to the condition of the method of Patent Document 1 which is a conventional technique.

  Tests 3 to 6 were the tensile tests performed on the bolts subjected to the processing procedure of FIG. 1. Here, “the load stress ratio (%) to σB” is a load corresponding to the tensile strength described in S12. The magnitude of the axial load against the magnitude of Therefore, σB indicates the tensile strength. Hereinafter, (axial load load / load corresponding to tensile strength) will be described as a load stress ratio unless otherwise specified. Test 3 is a tensile test of a bolt which was processed at a temperature of bluing treatment of 200 ° C. and using the bluing treatment time and the load stress ratio as parameters. Similarly, test 4 has a bluing treatment temperature of 250 ° C., test 5 has a bluing treatment temperature of 300 ° C., test 6 has a bluing treatment temperature of 400 ° C., respectively, It is the tension test of the bolt processed using load stress ratio as a parameter.

  Test 7 is a comparative test, and here is a tensile test for a material that has been conventionally tempered and bolted and tempered after rolling. As the tempered bolt, a material of SCM440, which was tempered at 880 ° C. and tempered at 540 ° C., was used. According to this result, it is understood that the tempered bolt has a tensile strength lower than that of the test 2 but has a yield ratio of 0.90 or more.

  FIG. 5 is a diagram showing a result of an experiment conducted in more detail with respect to the related art in which the blueing process is performed after the bolt forming in relation to the test 2. FIG. Here, the time of the blueing treatment is fixed at 30 minutes, the temperature of the blueing treatment is taken on the horizontal axis, and the tensile strength and yield ratio, which are the results of the tensile test of each bolt after each treatment, are taken on the vertical axis. is there. As can be seen from these results, in the prior art with only bolt forming and bluing treatment, the yield ratio stays slightly above 0.8, and the tensile strength decreases as the treatment temperature increases.

  FIG. 6 is a diagram showing the results of a relaxation test for the prior art bolt of Test 2 and the tempered bolt of Test 7. FIG. Here, in the relaxation test, an axial load corresponding to 0.2% proof stress of the tensile test is applied to each bolt and the crosshead displacement of the tensile test is held constant, and the load at each holding time is maintained. The change of was performed by calculating | requiring the load decreasing rate from an initial load. In FIG. 6, with respect to a normal temperature relaxation test where the test temperature of the relaxation test is normal temperature and a high temperature holding relaxation test where the test temperature is 150 ° C., the horizontal axis indicates the holding time, and the vertical axis indicates the load reduction rate. Thus, it can be seen that the bolts of the prior art bolt forming + bluing treatment are inferior in relaxation properties compared to the tempered bolts.

  Thus, what performed only the bluing process of a prior art after bolt shaping | molding has a low yield ratio as mentioned above, and its load reduction rate in a relaxation test is large. The reason can be considered as follows. That is, relaxation is a phenomenon in which internal stress is reduced by a so-called creep phenomenon due to dislocation movement, and is related to the yield ratio. High relaxation means a decrease in the axial load after fastening the bolt to the object, that is, a so-called reduction in the axial force, which may cause loosening during actual use of the bolt and cause fatigue failure . On the other hand, tempered bolts generally have a higher yield ratio than non-tempered bolts because movable dislocations are pinned by an alloy compound by tempering heat treatment by quenching and tempering. In the case of non-tempered bolts, bluing treatment corresponds to the tempering heat treatment.

  However, as described in connection with the process of S10 in FIG. 1, the bolt forming in test 2 is about 50% of the surface reduction rate after a patenting process, and about the surface reduction rate of a general non-tempered bolt. High compared to 30%. Therefore, it has a higher dislocation density than a general non-tempered bolt. This is because the dislocation pinning effect is considered to be weak only by the brewing treatment because the movable dislocation is proliferated remarkably by subsequent bolt rolling, and this is presumed to be one of the reasons that the yield ratio is lowered in Test 2. Therefore, a yield ratio comparable to a tempered bolt can be considered as one index for improving the relaxation characteristics.

  FIGS. 7 to 14 are graphs of the results of tests 3 to 6 in FIG. 4, with the load stress ratio as a parameter, the horizontal axis representing the blueing time on the logarithmic axis, and the vertical axis representing the yield ratio. Alternatively, the tensile strength is shown. For example, FIG. 7 and FIG. 8 show the yield ratio and tensile stress for the bolts under each processing condition corresponding to Test 3. FIG. Similarly, FIGS. 9 and 10 show the bolts under the respective processing conditions corresponding to the test 4, FIGS. 11 and 12 show the bolts under the respective processing conditions corresponding to the test 5, and FIGS. 6 shows the yield ratio and tensile stress for the bolts under each processing condition corresponding to 6. From these results, it can be seen that all bolts satisfy the target with a tensile strength of 1500 Mpa or more, but a yield ratio of 0.9 or more, which is the same as a tempered bolt, can be obtained depending on conditions. In addition, those with a yield ratio of 0.9 or more are shown shaded in the column of the yield ratio data in FIG.

  Here, a bolt having a yield ratio equal to or higher than that of the tempered bolt, that is, a bolt having a yield ratio of 0.90 or more, that is, a bolt having undergone the process of FIG. 1, was subjected to a relaxation test, and compared with the result of FIG. The results are shown in FIGS. FIG. 15 shows the results of the room temperature relaxation test, and FIG. 16 shows the results of the high temperature relaxation test. The contents of the relaxation test and the meanings of the vertical and horizontal axes in FIGS. 15 and 16 are the same as those described in FIG. In the drawing, 0.95σB or the like indicates that the bolt has a yield ratio of 0.95, that is, a bolt that has undergone the process of FIG. From these figures, the bolts with a yield ratio equal to or higher than tempered bolts, that is, with a yield ratio of 0.90 or more, have improved relaxation characteristics compared to the conventional bolting + bluing process. In addition, it can be seen that it is improved to the same level as the tempered bolt or more.

  Therefore, with reference to FIGS. 7, 9, 11, and 13, the processing time at which the yield ratio is 0.9 or more was obtained at each processing temperature. This is summarized in FIG. FIG. 17 shows the blueing treatment temperature on the horizontal axis and the blueing treatment time on the logarithmic axis on the vertical axis. In FIGS. The area surrounded by them is indicated by diagonal lines. This shaded area is considered to be a processing condition range for obtaining a yield ratio of 0.9 or more. The treatment condition ranges are 200 ° C. for 5 minutes, and 200 ° C. for 60 minutes, and 250 ° C. for 1 minute, and 250 ° C. for 10 minutes, and 300 ° C. for 0.5 minutes, and 300 ° C. for 5 minutes, and It is an area surrounded by connecting each processing condition at 400 ° C. for 0.5 minute and 400 ° C. for 1 minute.

  Thus, in the procedure of the method for manufacturing the non-tempered high-strength bolt in FIG. 1, the load stress ratio of S12 is 80% or more and less than 100%, and the brewing condition of S16 is the processing condition range described in FIG. By doing so, it is possible to obtain a non-tempered high strength bolt having a tensile strength of 1500 MPa or more, a yield ratio of 0.9 or more, and improved relaxation characteristics.

  FIG. 18 is a flowchart showing another processing procedure for the method of manufacturing the non-tempered high-strength bolt. This manufacturing method differs from the method described with reference to FIG. 1 in the load loading step (S20) for applying plastic strain with a tension jig, and further, the blueing treatment can be omitted.

  In FIG. 18, the process of bolt forming (S10) is exactly the same as the content described in the bolt forming process of FIG. Accordingly, a piano wire material is prepared, patented, drawn at a predetermined area reduction ratio, the tensile strength is changed from 1500 MPa to 1700 MPa, and the outer shape of the bolt is formed by rolling and head forming. .

  The formed bolt is subjected to an axial load under the condition that the load stress ratio is higher than that of the manufacturing method of FIG. For the load application, the tension jig described with reference to FIG. 3 is used. Thereafter, it is unloaded (S14). This unloading process is exactly the same as the contents described in the unloading process of FIG. This completes the method for producing the non-tempered high-strength bolt in FIG. Here, the bluing process by the heat treatment is omitted, but it can be said that the strain aging process is performed at room temperature if the view is changed.

  Therefore, in the load loading step (S20), various treatments were performed on the bolts using the load stress ratio and the holding time for holding the load load, that is, the time until unloading as parameters, and then a tensile test was performed. As the evaluation index, as described above, a yield ratio equal to or higher than that of the tempered bolt is 0.90 or higher.

  FIG. 19 is a diagram showing the results of a tensile test as to Test 8 for each bolt subjected to the treatment using various load stress ratios after bolt formation and the load holding time as parameters. Here, for reference, the data of Test 1, Test 2, and Test 7 described in FIG. 4 are transcribed. FIG. 20 and FIG. 21 are graphs of the results of Test 8, each using the load stress ratio as a parameter, taking the load holding time on the logarithmic axis on the horizontal axis and taking the yield ratio or tensile strength on the vertical axis. It is shown.

  From these results, it can be seen that all bolts satisfy the target with a tensile strength of 1500 Mpa or more, but a yield ratio of 0.9 or more, which is the same as a tempered bolt, can be obtained depending on conditions. It can be seen that the condition does not depend on the load loading time and the load stress ratio is 90% or more. Note that those with a yield ratio of 0.9 or more are shaded in the column of yield ratio data in FIG.

  Thus, in the procedure of the manufacturing method of the non-tempered high strength bolt in FIG. 18, the tensile strength is 1500 MPa or more and the yield ratio is 0.9 by setting the load stress ratio of S20 to 90% or more and less than 100%. As described above, a non-tempered high-strength bolt with improved relaxation characteristics can be obtained.

  FIG. 22 is a flowchart showing yet another processing procedure for the method of manufacturing a non-tempered high strength bolt. Compared with the method described in FIG. 1, in this manufacturing method, the brewing process (S22) is arranged next to the bolt forming step (S10), and accordingly, a load loading step (plastic load is applied by a tension jig) ( The difference in the content of S24) is different. The manufacturing method of FIG. 22 is related to the manufacturing method described in FIG. 18, that is, by increasing the load stress ratio, so that heat treatment after unloading can be omitted due to effects such as room temperature strain aging. When the ratio is increased, it is based on the idea that the characteristics may be further improved by performing blueing treatment in advance.

  In the procedure of the manufacturing method of FIG. 22, the bolt forming (S10) step is exactly the same as the content described in the bolt forming step of FIG. Accordingly, a piano wire material is prepared, patented, drawn at a predetermined area reduction ratio, the tensile strength is changed from 1500 MPa to 1700 MPa, and the outer shape of the bolt is formed by rolling and head forming. . Once the bolt is formed, a brewing process is performed (S22). Then, a load loading step (S24) for applying plastic strain with a tension jig is performed and unloaded (S14). This unloading process is exactly the same as the contents described in the unloading process of FIG.

  Here, the content of the bluing treatment step (S22) was the same as that used in the prior art method, that is, 250 ° C. for 30 minutes. Then, in the load loading step (S24), as in the load loading step (S20) in FIG. 18, the load stress ratio and the time for holding the load load, that is, the time until unloading, are used as parameters. The treatment was performed and then a tensile test was performed. As the evaluation index, as described above, a yield ratio equal to or higher than that of the tempered bolt is 0.90 or higher.

  FIG. 23 is a diagram showing the results of a tensile test as to test 9 for each bolt subjected to the treatment using various load stress ratios and the load holding time as parameters after the bolt forming. Here, for reference, the data of Test 1, Test 2, and Test 7 described in FIG. 4 are transcribed. FIGS. 24 and 25 are graphs of the results of Test 9, each using the load stress ratio as a parameter, the horizontal axis taking the load holding time on the logarithmic axis, and the vertical axis taking the yield ratio or tensile strength. It is shown.

  From these results, it can be seen that the target with a tensile strength of 1500 Mpa or more is sufficiently satisfied over all the bolts, and is considerably improved as compared with, for example, the case without the pre-bluening treatment in FIG. Moreover, about yield ratio, it turns out that 0.9 or more like a tempered bolt is obtained depending on conditions. It can be seen that the condition does not depend on the load loading time and the load stress ratio is 90% or more. Note that those with a yield ratio of 0.9 or more are shaded in the column of yield ratio data in FIG. In addition, the pre-blowing treatment condition is 250 ° C. for 30 minutes in the prior art, but the temperature range may be 200 ° C. to 250 ° C., and the time range may be 15 minutes to 30 minutes.

  In this way, in the procedure of the method for manufacturing the non-tempered high-strength bolt in FIG. 22, the bluing treatment condition of S22 is set to 200 ° C. to 250 ° C. for 30 minutes, and the load stress ratio of S24 is set to 90% to 100%. By making it less than the above, it is possible to obtain a non-tempered high strength bolt having a tensile strength of 1500 MPa or more, a yield ratio of 0.9 or more, and improved relaxation characteristics.

  FIG. 26 shows a method for producing a non-tempered high-strength bolt in the case where a load-carrying method, more specifically, a jig for loading a load is not a tension jig but a rotary fastening jig. It is a flowchart which shows a procedure. Here, compared with the manufacturing method of FIG. 1, the load loading process (S30) which gives a plastic strain with a rotation fastening jig | tool differs, and other bolt shaping | molding (S10), unloading (S14), blueing process ( Step S16) is exactly the same as the corresponding step in FIG.

  In other words, in the manufacturing method of FIG. 26, the load application step in FIG. 1 applies a predetermined plastic strain by pulling both ends of the bolt with a tensioning device, and this is equivalent to the plastic region tightening method of the bolt. A load is applied in the axial direction of the magnitude so as to give the same predetermined plastic strain. Therefore, the degree to which the plastic region is tightened by the rotary tightening jig is determined such that the magnitude of the axial load load thereby becomes the same as the load stress ratio described in relation to FIG. By doing so, it is possible to obtain a non-heat treated high strength bolt having exactly the same characteristics as the non-heat treated high strength bolt described in FIG.

  In the load loading step (S30) for applying plastic strain with the rotary tightening jig, the bolt is tightened until the elastic limit is exceeded, as in the load loading step (S12) for applying plastic strain with the tension jig, and the screw portion is arbitrarily selected. It is the process of giving the plastic strain of. As described in relation to S12, the plastic strain is preferably applied to a portion that is not a so-called fitting portion that fits with the other screw portion when the bolt is attached to an actual device or the like. In addition, it is also preferable that the plastic strain is provided to a portion where the bolt extends when the bolt is fastened, that is, a screw portion that is not a fitting portion. That is, as described with reference to FIGS. 2A and 2B, with respect to the stud bolt 10, this plastic strain is a portion other than the use fitting portion 14 in the screw portion 12, that is, in actual use. It is preferable that plastic distortion occurs in the bare screw portion 15 when used without being fitted to the female screw on the other side, and the hexagon bolt 20 is also bare when used except for the fitting portion 24 within the screw portion 22. It is preferable that plastic strain occurs in the screw portion 25.

  FIG. 27 is a diagram for explaining the structure and operation of a rotary tightening jig for applying plastic strain to a bare screw portion other than the bolt use fitting portion. About the bolt, the same code | symbol is attached | subjected to the element similar to the tension jig | tool of FIG. 3, and detailed description is abbreviate | omitted. FIG. 27A shows a stud bolt rotary tightening jig 50 for applying plastic strain to the stud bolt 10. The stud bolt rotary tightening jig 50 includes a screwing jig 52 into which the screw part 12 on one side of the stud bolt 10 is screwed and a nut 54 to be fitted into the screw part 12 on one side of the stud bolt 10. The

  The screwing jig 52 is a cylindrical member having an overall height of a length J that is shorter than the entire length of the stud bolt 10, and has a center hole into which the stud bolt 10 can be inserted, and a female screw having an effective length L3 at the bottom of the center hole. The part 18 is cut. L3 is set shorter than the effective length L1 of the threaded portion 12 of the stud bolt 10 and longer than the length L2 of the use fitting portion 14 of the stud bolt 10. The axial length J of the screwing jig 52 is such that when the threaded part 12 on one side of the stud bolt is screwed into the entire female threaded part 18, the threaded part 12 on the other side of the stud bolt 10 does not protrude entirely. Set to length. At that time, the nut 54 is set so that the axial height of the nut 54 is shorter than the length of the portion where the screw portion 12 on the other side of the stud bolt 10 protrudes.

  Using the stud bolt rotary tightening jig 50 having such a configuration, the screw part 12 on one side of the stud bolt 10 is first passed through the center hole of the screwing jig 52 and the female thread part 18 at the bottom thereof The screw part 12 at the tip is fitted. Then, the nut 54 is fitted into the screw portion 12 on the other side of the stud bolt 10 protruding from the screwing jig 52, and turned until the nut 54 stops on the upper surface of the screwing jig 52. As shown in FIG. 27A, two bare screw portions 16 appear between the retaining surface of the nut 54 that is the upper surface of the screwing jig 52 and the female screw portion 18. The axial length L4 of the two bare screw portions 16 is preferably the same, but may be different.

  In this state, the stud bolt 10 is attached to the stud bolt rotary fastening jig 50. Thereafter, the nut 54 is screwed into the screwing jig 52 by a plastic zone fastening method using a rotating device (not shown). On the other hand, the stud bolt 10 is tightened by the θ rotation shown in FIG. The plastic zone tightening method is a method of further tightening from the snag torque to give an axial strain exceeding the elastic limit of the material of the bolt, and the amount of strain giving the plastic strain can be arbitrarily set by the size of the tightening. it can.

  FIG. 28 is a diagram for explaining the relationship between the snag torque and the additional tightening angle in the plastic region tightening method. In this figure, the horizontal axis represents the rotation angle, and the vertical axis represents the magnitude of torque received by the bolt. This torque-rotation angle characteristic corresponds to the stress-strain diagram of the bolt. Here, the snag torque is one of the indices indicating the elastic region of the material. The last part of the linear region in the torque-rotation angle characteristic is considered as the yield start point A of the material, and the state further rotated by 10 ° therefrom. Assuming that point B is the point C and the state when 90 ° rotation is returned from point B is point C, the torque at point C is called the snag torque. Retightening is a method of reliably entering the plastic region based on this snag torque.

  Returning to FIG. 27 again, FIG. 27B shows a hexagon bolt rotary tightening jig 60 for applying plastic strain to the hexagon bolt 20. The hexagon bolt rotary tightening jig 60 is screwed with the screw portion 22 of the hexagon bolt 20, and is approximately the length of the shaft portion including the screw portion 22 having an effective length L <b> 1 below the head portion 21 of the hexagon bolt 20. A cylindrical member having the same overall height, which can be inserted into the shaft portion of the hexagon bolt 20, has a central through hole with an inner diameter smaller than the outer shape of the head 21, and an effective length at the back of the central through hole The female screw part 18 of L3 is cut. L3 is set to be shorter than the effective length L1 of the screw portion 12 of the hexagon bolt 20 and longer than the length L2 of the use fitting portion 14 of the hexagon bolt 20.

  Using the hexagon bolt rotary tightening jig 60 having such a configuration, the shaft portion of the hexagon bolt 20 is passed through the center through hole, and the screw portion 22 at the tip is fitted to the female screw portion 18 at the bottom. Then, the head 21 is rotated until it stops at the upper surface of the hexagon bolt rotary fastening jig 60. As shown in FIG. 27 (b), the dimensional relationship at this time is between the female screw portion 18 and the bare screw portion 16 between the stop surface of the head 21 that is the upper surface of the hexagon bolt rotary tightening jig 60 and the female screw portion 18. Appears.

  In this state, the hexagon bolt 20 is attached to the rotary tightening jig 60 for the hexagon bolt. Therefore, as described in relation to FIG. 27A, after that, using a rotating device (not shown), the head 21 is attached to the hexagon bolt rotary fastening jig 60 by the plastic zone fastening method as shown in FIG. The stud bolt 10 is tightened by the θ rotation shown in b) to apply an axial load to the stud bolt 10. The load stress ratio can be arbitrarily set by the magnitude of the additional tightening from the snag torque.

  Thus, in both the case of the stud bolt 10 and the case of the hexagon bolt 20, the rotary tightening jig is shorter than the effective length L1 of the screw portion of the bolt, and the bolt is used to be fitted to the counterpart in actual use. It has a shape in which the screw portion of the bolt is fitted to at least a part of an arbitrary length L3 longer than the fitting length L2, and the screw portion of the bolt that gives plastic strain is formed on the L3 of the rotary fastening jig. Fit at least part of the part, attach the bolt to the rotary tightening jig, tighten from the snag torque by the plastic zone tightening method, and give plastic strain to the bare screw part as in the case of the tension jig it can. In FIG. 27 (a), the nut is used as the rotary tightening jig. However, a member having a shape that can be easily attached to the rotating device, such as a plate member having a female screw cut, may be used.

  Therefore, the load loading step (S30) is the same as the load loading step (S12) in FIG. 1 in that only a jig is different and a load is applied in the axial direction of the bolt to apply plastic strain. As described with reference to FIG. 1, the relationship between the degree of load loading in the load loading step (S30) by the plastic zone tightening method and the processing conditions in the brewing step (S16) is the yield ratio. Relaxation characteristics can be improved by evaluating 0.9 or more as one index.

  Here, the experiment conducted to determine the magnitude of the load applied in S30 and the heat treatment condition range performed in S16 will be described. Here, a large number of bolts formed in S12 are prepared, and the magnitude of the applied load is changed at 90 °, 180 °, and 270 ° at the tightening angle, and the heat treatment conditions are 200 ° C. for 30 minutes and 300 ° C. 3 minutes and 400 ° C. for 1 minute. As the heat treatment conditions, representative points were selected from the treatment condition range shown in FIG. 17 obtained when the tension jig was used. The bolts thus treated were each subjected to a tensile test to determine tensile strength, 0.2% proof stress, and yield ratio.

  The result is shown in FIG. FIG. 30 is a graph of the results of FIG. 29, with the bluing process conditions as parameters, the horizontal axis indicating the tightening angle, and the vertical axis indicating the yield ratio. 29 and 30 also partially show the results of Example 5 described later.

  From these results, it can be seen that all bolts satisfy the target with a tensile strength of 1500 Mpa or more, but the yield ratio is 0.9 or more, which is the same as a tempered bolt, under all conditions. Note that those with a yield ratio of 0.9 or more are shaded in the yield ratio data column in FIG. Thus, by setting the retightening angle of S20 to 90 degrees or more and 270 degrees or less, the tensile strength is 1500 MPa or more and the yield ratio under the typical conditions in the treatment condition range for the blueing treatment described in FIG. Can be 0.9 or more. From this, it is expected that the retightening angle of 90 degrees or more and 270 degrees or less corresponds to a load stress ratio of 80% or more in the case of the tension jig. Therefore, the bluing condition is the processing condition range of FIG. It is thought that it can be used.

  Here, the bolt which passed through the process of FIG. 26 which has the yield ratio 0.90 or more was selected, and the relaxation test was done. The results are shown in FIGS. These figures correspond to FIGS. 15 and 16 using a tension jig. FIG. 31 shows the result of the normal temperature relaxation test, and FIG. 32 shows the result of the high temperature relaxation test. The contents of the relaxation test and the meanings of the vertical and horizontal axes in FIGS. 31 and 32 are the same as those described with reference to FIG. 15 and the like, and the conventional technology and tempered bolt data are also shown for comparison. In the drawing, 0.93σB or the like is the same for a bolt having a yield ratio of 0.93. From these figures, the bolts with a yield ratio equal to or higher than tempered bolts, that is, with a yield ratio of 0.90 or more, have improved relaxation characteristics compared to the conventional bolting + bluing process. In addition, it can be seen that it is improved to the same level as the tempered bolt or more. Moreover, it turns out that it is the same result as what is based on a tension jig.

  Therefore, in the procedure of the manufacturing method of the non-tempered high-strength bolt in FIG. 26, the tightening angle of S30 is set to 90 degrees or more and 270 degrees or less, and the blueing condition of S16 is set to the processing condition range described in FIG. A non-tempered high strength bolt having a tensile strength of 1500 MPa or more and a yield ratio of 0.9 or more and improved relaxation characteristics can be obtained.

  FIG. 33 is a flowchart showing another processing procedure using a rotary tightening jig in the method for producing a non-tempered high-strength bolt. This manufacturing method corresponds to the method described in FIG. That is, instead of the load loading step (S20) for applying plastic strain with a tension jig, the load loading step (S32) applies plastic strain with a rotary fastening jig. Then, the bluing process can be omitted as in the method of FIG.

  In FIG. 33, the bolt forming step (S10) and the unloading step (S14) are the same as those described so far. The load loading step (S32) differs from the load loading step (S30) of FIG. 26 only in the degree of load load, and the method of arbitrarily setting the amount of strain that gives plastic strain by retightening with a rotary tightening jig is the same. It is.

  Therefore, in the load application step (S32), various treatments were performed on the bolt using the additional tightening angle as a parameter, and then a tensile test was performed. As the evaluation index, as described above, a yield ratio equal to or higher than that of the tempered bolt is 0.90 or higher.

  The results are shown in FIGS. 29 and 30. As can be seen from this result, all bolts satisfy the target with a tensile strength of 1500 Mpa or more, but the yield ratio is 0.9 or more, which is the same as that of a tempered bolt, depending on conditions. The condition is that the tightening angle is not less than 180 degrees and not more than 270 degrees. Note that those with a yield ratio of 0.9 or more are shaded in the yield ratio data column in FIG.

  Thus, in the procedure of the manufacturing method of the non-tempered high strength bolt in FIG. 33, the tensile strength is 1500 MPa or more and the yield ratio is 0.9 by setting the retightening angle of S32 to 180 degrees or more and 270 degrees or less. As described above, a non-tempered high-strength bolt with improved relaxation characteristics can be obtained.

  FIG. 34 is a flowchart showing still another processing procedure using a rotary tightening jig in the method for producing a non-tempered high-strength bolt. This manufacturing method corresponds to the method described in FIG. That is, instead of the load loading step (S24) in which plastic strain is applied with a tension jig, the load loading step (S34) applies plastic strain with a rotary tightening jig. Further, the brewing process (S22) having the same contents as in FIG. 22 is arranged next to the bolt forming process (S10).

  In FIG. 34, the bolt forming step (S10) and the unloading step (S14) are the same as those described so far. The load loading step (S34) differs from the load loading step (S30) in FIG. 26 only in the degree of load loading, and the method of arbitrarily setting the amount of strain that gives plastic strain by retightening with a rotary tightening jig is the same. It is.

  Here, the content of the bluing treatment step (S22) was the same as the bluing treatment step of FIG. 22 as described above, that is, 250 ° C. for 30 minutes used in the method of the prior art. In the load application step (S34), various treatments were performed on the bolts using the additional tightening angle as a parameter, and then a tensile test was performed. As the evaluation index, as described above, a yield ratio equal to or higher than that of the tempered bolt is 0.90 or higher.

  The result is shown in FIG. FIG. 36 shows the relationship between the additional tightening angle and the yield ratio, and FIG. 37 shows the relationship between the additional tightening angle and the tensile strength. As can be seen from these results, it can be seen that all bolts satisfy the target with a tensile strength of 1500 Mpa or more, and that the yield ratio is 0.9 or more, which is the same as a tempered bolt, under all conditions. Further, as described with reference to FIG. 22, the condition of the pre-blueing process may be 200 ° C. for 30 minutes.

  In this way, in the procedure of the method for producing the non-tempered high-strength bolt in FIG. 34, the bluing treatment condition of S22 is set to 200 ° C. to 250 ° C. for 30 minutes, and the retightening angle of S34 is set to 90 ° to 270 °. By setting it as below, it is possible to obtain a non-tempered high-strength bolt having a tensile strength of 1500 MPa or more, a yield ratio of 0.9 or more, and improved relaxation characteristics.

3 is a flowchart showing a processing procedure of a method for manufacturing a non-tempered high-strength bolt in Example 1. In embodiment which concerns on this invention, it is a figure explaining a mode that a plastic strain is given to a high intensity | strength bolt. In embodiment which concerns on this invention, it is a figure explaining the structure and effect | action of a tension jig. In Example 1, it is a figure which shows the result of the tension test about the bolt of various parameters. It is a figure which shows the relationship between the blueing process conditions and the result of a tension test about the prior art which performs a blueing process after bolt shaping | molding. It is a figure which shows the result of the relaxation test about the bolt of a prior art, and a tempered bolt. In Example 1, it is a figure which shows the result of the tension test about the bolt of 200 degreeC blueing. In Example 1, it is a figure which shows the result of the tension test about the bolt of 200 degreeC blueing. In Example 1, it is a figure which shows the result of the tension test about the bolt of 250 degreeC blueing. In Example 1, it is a figure which shows the result of the tension test about the bolt of 250 degreeC blueing. In Example 1, it is a figure which shows the result of the tension test about the bolt of 300 degreeC blueing various parameters. In Example 1, it is a figure which shows the result of the tension test about the bolt of 300 degreeC blueing various parameters. In Example 1, it is a figure which shows the result of the tension test about the bolt of 400 degreeC brewing various parameters. In Example 1, it is a figure which shows the result of the tension test about the bolt of 400 degreeC brewing various parameters. It is a figure which shows the result of the normal temperature relaxation test about the volt | bolt of Example 1. FIG. It is a figure which shows the result of the high temperature relaxation test about the volt | bolt of Example 1. FIG. It is a figure which shows the brewing process condition range in Example 1. FIG. It is a flowchart which shows the process sequence of the manufacturing method of the non-tempered high intensity | strength bolt in Example 2. FIG. In Example 2, it is a figure which shows the result of the tension test about the bolt of various parameters. FIG. 20 is a graph of the result of FIG. 19. FIG. 20 is a graph of the result of FIG. 19. It is a flowchart which shows the process sequence of the manufacturing method of the non-tempered high intensity | strength bolt in Example 3. FIG. In Example 3, it is a figure which shows the result of the tension test about the bolt of various parameters. FIG. 24 is a graph showing the result of FIG. 23. FIG. 24 is a graph showing the result of FIG. 23. It is a flowchart which shows the process sequence of the manufacturing method of the non-tempered high intensity | strength volt | bolt in Example 4. In embodiment which concerns on this invention, it is a figure explaining the structure and effect | action of a rotation fastening jig | tool. In embodiment which concerns on this invention, it is a figure explaining the relationship between the snag torque by a plastic zone fastening method, and retightening. In Example 4, 5, it is a figure which shows the result of the tension test about the bolt of various parameters. FIG. 30 is a graph showing the result of FIG. 29. It is a figure which shows the result of the normal temperature relaxation test about the volt | bolt of Example 4. FIG. It is a figure which shows the result of the high temperature relaxation test about the volt | bolt of Example 4. FIG. It is a flowchart which shows the process sequence of the manufacturing method of the non-tempered high intensity | strength volt | bolt in Example 5. It is a flowchart which shows the process sequence of the manufacturing method of the non-tempered high intensity | strength volt | bolt in Example 6. In Example 6, it is a figure which shows the result of the tension test about the bolt of various parameters. FIG. 36 is a graph showing the result of FIG. FIG. 36 is a graph showing the result of FIG.

Explanation of symbols

  10 Stud bolts, 12, 22 threaded parts, 14, 24 Use fitting parts, 15, 16, 25, 26 Bare threaded parts, 18 Female threaded parts, 20 Hexagon bolts, 21 Heads, 30, 50 Tensile treatment for stud bolts Tools, 40, 60 Hexagon bolt tension jig, 42, 54 nut, 44 upper jig, 46 lower jig, 52 screw jig.

Claims (9)

A load-loading step of applying plastic load by applying an axial load corresponding to 80% or more and less than 100% of the tensile strength of the bolt using an arbitrary tensile jig after forming the non-tempered bolt;
Unloading process to unload and remove the bolt from the jig;
In relation to the temperature and time for heat treatment of the removed bolt, 5 minutes at 200 ° C., 60 minutes at 200 ° C., 1 minute at 250 ° C., 10 minutes at 250 ° C., and 0.5 minute at 300 ° C. And a treatment step of performing a blueing treatment in a treatment condition range surrounded by treatment conditions of 300 ° C. for 5 minutes, 400 ° C. for 0.5 minute, and 400 ° C. for 1 minute;
A method for producing a non-tempered high-strength bolt, comprising: A load-loading step of applying plastic strain by applying an axial load corresponding to 90% or more and less than 100% of the tensile strength of the bolt using an arbitrary tension jig after forming the non-tempered bolt;
Unloading process to remove the bolt from the tension jig
A method for producing a non-tempered high-strength bolt, comprising: After forming the non-tempered bolt, a treatment step of performing a blueing treatment with a treatment temperature range of 200 ° C. or more and 250 ° C. or less and a treatment time range of 15 minutes or more and 30 minutes or less,
A load-loading step of applying an axial load corresponding to 90% or more and less than 100% of the tensile strength of the bolt using an arbitrary tension jig to impart plastic strain to the non-tempered bolt after the blueing treatment,
Unloading process to remove the bolt from the tension jig
A method for producing a non-tempered high-strength bolt, comprising: In the manufacturing method of the non-tempered high intensity | strength bolt of any one of Claim 1 to 3,
The tension jig is
At least part of the portion of the arbitrary length L3 that is shorter than the effective length L1 of the threaded portion of the bolt after molding and longer than the use fitting length L2 that the bolt is fitted to the other party in actual use. It has a shape to fit the screw part,
The loading process is
An attaching step of fitting the bolt to the tension jig by fitting the screw portion of the bolt giving plastic strain with at least a part of the length L3 of the tension jig;
A tensioning step of pulling a bolt attached to a tensioning jig in an axial direction under an arbitrary axial load;
A method for producing a non-tempered high-strength bolt, comprising: After forming the non-tempered bolt, a load loading step of tightening with an arbitrary snag torque of the bolt using an arbitrary rotary tightening jig and further tightening at an angle of 90 degrees to 270 degrees;
Unloading process to unload and remove the bolt from the jig;
In relation to the temperature and time for heat treatment of the removed bolt, 5 minutes at 200 ° C., 60 minutes at 200 ° C., 1 minute at 250 ° C., 10 minutes at 250 ° C., and 0.5 minute at 300 ° C. And a treatment step of performing a blueing treatment in a treatment condition range surrounded by treatment conditions of 300 ° C. for 5 minutes, 400 ° C. for 0.5 minute, and 400 ° C. for 1 minute;
A method for producing a non-tempered high-strength bolt, comprising: After forming the non-tempered bolt, a load loading step of tightening with an arbitrary snag torque of the bolt using an arbitrary rotary tightening jig and further tightening at an angle of 180 degrees to 270 degrees;
Unloading process to remove and remove the bolt from the rotary tightening jig,
A method for producing a non-tempered high-strength bolt, comprising: After forming the non-tempered bolt, a treatment step of performing a blueing treatment with a treatment temperature range of 200 ° C. or more and 250 ° C. or less and a treatment time range of 15 minutes or more and 30 minutes or less,
A load-loading step of tightening the non-tempered bolt after the blueing treatment with an arbitrary snug torque of the bolt using an arbitrary rotary tightening jig, and further tightening at an angle of 90 degrees to 270 degrees;
Unloading process to remove and remove the bolt from the rotary tightening jig,
A method for producing a non-tempered high-strength bolt, comprising: In the manufacturing method of the non-tempered high intensity | strength bolt of any one of Claim 5 to 7,
A high-strength bolt is a headed bolt having a head with a diameter larger than the shaft diameter,
The rotary tightening jig has a screw portion of an arbitrary length L3 that is shorter than the effective length L1 of the screw portion of the bolt and longer than the use fitting length L2 that the bolt is fitted to the counterpart in actual use. Including a through hole in the part, and when the head-attached bolt is inserted into the through hole, screwed into the screw part and fitted with a length of L3, the head part has a shape that stops at the end of the through hole,
The loading process is
An attachment process in which the head bolt is screwed in and attached until the head stops at the end of the rotary tightening jig;
A tightening step of tightening the bolt with the head with a snag torque of an arbitrary size while the head is stopped at the end of the rotary tightening jig;
A retightening step of retightening the bolt with head at an arbitrary angle from the tightened state of the snag torque;
A method for producing a non-tempered high-strength bolt, comprising: In the manufacturing method of the non-tempered high intensity | strength bolt of any one of Claim 5 to 7,
High-strength bolts are stud bolts that have threaded portions at least at both ends of the shaft,
The rotary tightening jig has a screw portion of an arbitrary length L3 that is shorter than the effective length L1 of the screw portion of the bolt and longer than the use fitting length L2 that the bolt is fitted to the counterpart in actual use. When the stud bolt is inserted into the hole, screwed into the threaded portion, and the threaded portion at one end thereof is fitted to the length of L3, the other end of the stud bolt protrudes more than L2 from the end of the hole. With shape,
The loading process is
Insert the stud bolt into the hole of the rotary tightening jig, screw it into the screw part, fit the screw part at one end with the length of L3, and tighten the nut on the other end of the stud bolt protruding from the end of the hole Mounting process for attaching,
A tightening process of rotating the tightening nut until it stops at the end of the hole, and then tightening the stud bolt with a snag torque of any size;
A retightening step of retightening the tightening nut at an arbitrary angle from the tightened state of the snag torque;
A method for producing a non-tempered high-strength bolt, comprising:

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