US20090003968A1 - Bolt and Manufacturing Method of Bolt - Google Patents

Bolt and Manufacturing Method of Bolt Download PDF

Info

Publication number
US20090003968A1
US20090003968A1 US12/087,603 US8760307A US2009003968A1 US 20090003968 A1 US20090003968 A1 US 20090003968A1 US 8760307 A US8760307 A US 8760307A US 2009003968 A1 US2009003968 A1 US 2009003968A1
Authority
US
United States
Prior art keywords
bolt
male screw
nut
screw
present
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US12/087,603
Other languages
English (en)
Inventor
Norikazu Tezuka
Kazuharu Hirokawa
Keisuke Ihara
Kei Osawa
Hiroshi Ishikawa
Taiji Torigoe
Ryuichi Yamamoto
Yukihiro Hashimoto
Nobuyuki Izutsu
Koji Takahashi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mitsubishi Heavy Industries Ltd
Original Assignee
Mitsubishi Heavy Industries Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mitsubishi Heavy Industries Ltd filed Critical Mitsubishi Heavy Industries Ltd
Assigned to MITSUBISHI HEAVY INDUSTRIES, LTD. reassignment MITSUBISHI HEAVY INDUSTRIES, LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: HASHIMOTO, YUKIHIRO, HIROKAWA, KAZUHARU, IHARA, KEISUKE, ISHIKAWA, HIROSHI, IZUTSU, NOBUYUKI, OSAWA, KEI, TAKAHASHI, KOJI, TEZUKA, NORIKAZU, TORIGOE, TAIJI, YAMAMOTO, RYUICHI
Publication of US20090003968A1 publication Critical patent/US20090003968A1/en
Abandoned legal-status Critical Current

Links

Images

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24C—ABRASIVE OR RELATED BLASTING WITH PARTICULATE MATERIAL
    • B24C1/00—Methods for use of abrasive blasting for producing particular effects; Use of auxiliary equipment in connection with such methods
    • B24C1/10—Methods for use of abrasive blasting for producing particular effects; Use of auxiliary equipment in connection with such methods for compacting surfaces, e.g. shot-peening
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23G—THREAD CUTTING; WORKING OF SCREWS, BOLT HEADS, OR NUTS, IN CONJUNCTION THEREWITH
    • B23G9/00—Working screws, bolt heads, or nuts in conjunction with thread cutting, e.g. slotting screw heads or shanks, removing burrs from screw heads or shanks; Finishing, e.g. polishing, any screw-thread
    • B23G9/001—Working screws
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
    • B23P15/00—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
    • B23P9/00—Treating or finishing surfaces mechanically, with or without calibrating, primarily to resist wear or impact, e.g. smoothing or roughening turbine blades or bearings; Features of such surfaces not otherwise provided for, their treatment being unspecified
    • B23P9/04—Treating or finishing by hammering or applying repeated pressure
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0093—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for screws; for bolts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D5/00—Blades; Blade-carrying members; Heating, heat-insulating, cooling or antivibration means on the blades or the members
    • F01D5/02—Blade-carrying members, e.g. rotors
    • F01D5/06—Rotors for more than one axial stage, e.g. of drum or multiple disc type; Details thereof, e.g. shafts, shaft connections
    • F01D5/066—Connecting means for joining rotor-discs or rotor-elements together, e.g. by a central bolt, by clamps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16B—DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING
    • F16B33/00—Features common to bolt and nut
    • F16B33/06—Surface treatment of parts furnished with screw-thread, e.g. for preventing seizure or fretting
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2230/00—Manufacture
    • F05D2230/30—Manufacture with deposition of material
    • F05D2230/31—Layer deposition
    • F05D2230/311—Layer deposition by torch or flame spraying
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2230/00—Manufacture
    • F05D2230/90—Coating; Surface treatment
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2260/00—Function
    • F05D2260/94—Functionality given by mechanical stress related aspects such as low cycle fatigue [LCF] of high cycle fatigue [HCF]
    • F05D2260/941—Functionality given by mechanical stress related aspects such as low cycle fatigue [LCF] of high cycle fatigue [HCF] particularly aimed at mechanical or thermal stress reduction
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2300/00—Materials; Properties thereof
    • F05D2300/20—Oxide or non-oxide ceramics
    • F05D2300/21—Oxide ceramics
    • F05D2300/211—Silica
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2300/00—Materials; Properties thereof
    • F05D2300/20—Oxide or non-oxide ceramics
    • F05D2300/21—Oxide ceramics
    • F05D2300/2112—Aluminium oxides
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2300/00—Materials; Properties thereof
    • F05D2300/20—Oxide or non-oxide ceramics
    • F05D2300/22—Non-oxide ceramics
    • F05D2300/226—Carbides
    • F05D2300/2261—Carbides of silicon
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/47—Burnishing
    • Y10T29/479—Burnishing by shot peening or blasting

Definitions

  • the present invention relates to a bolt that is effective to be used in a place where a male screw is subject to a repetitive stress, and relates to a manufacturing method of the bolt.
  • An example of a bolt used in a place where a male screw is subject to a repetitive stress includes, for example, a rotor spindle bolt of a gas turbine or a stud bolt of an engine crank case. Referring to FIGS. 10 and 1A , description will be given below for a rotor spindle bolt of a gas turbine.
  • a reference numeral “100” denotes a rotor of a compressor of a gas turbine.
  • the rotor 100 is configured by: a plurality of discs 103 that are fastened by a rotor spindle bolt (a fastening bolt for the gas turbine), that is, a bolt 101 , and a nut 102 ; and moving blades 104 that are respectively fixed to the plurality of discs 103 .
  • the plurality of discs 103 are fastened by the plurality of bolts 101 and the plurality of nuts 102 that are disposed at approximately equal intervals in the circumferential direction of the discs 103 .
  • thermal extension difference is generated associated with starting up and stopping of the gas turbine, and an elongation and a shrinkage are caused by projections of fluctuating loads due to thrust, a centrifugal force, or a rotation of the rotor 100 with a deformation under the weight thereof. Therefore, the fastening force of the bolt 101 and the nut 102 is varied.
  • a fluctuating stress (a tensile stress and a bending stress) is applied to an engaging portion of a male screw of the bolt 101 and a female screw of the nut 102 , that is, a screw engaging portion 105 .
  • the screw engaging portion 105 When the fluctuating stress is applied to the screw engaging portion 105 , the screw engaging portion 105 tends to suffer from wear and fatigable damage. Therefore, improvement is necessary for a fatigue resistance (especially, a fretting fatigue resistance) of the screw engaging portion 105 , especially, the male screw of the bolt 101 .
  • Patent Document 1 and Patent Document 2 Techniques that improve the fatigue resistance of screw fastening members (for example, a bolt and a nut, and a stud bolt) are conventionally presented (for example, Patent Document 1 and Patent Document 2). Description will be given below for a bolt that is a conventional screw fastening member.
  • the bolt that is a conventional screw fastening member is a bolt formed by shaping a male screw that fits with a female screw, into a tapered shape in a direction along which the bolt is pulled (Patent Document 1).
  • Another bolt is a bolt formed by molding a bolt with a round portion beneath the bolt neck thereof that has the curvature radius within a range of 1.2 to 3.0 times as large as that of a round portion beneath the bolt neck of the finished product bolt and by shaping the round portion beneath the bolt neck of the bolt by applying cold working such that the portion has a predetermined curvature radius (Patent Document 2).
  • Patent Document 1 is a technique that equalizes the tensile stress applied on the male screw by shaping the male screw into the tapered shape in a direction along which the bolt is pulled, and is not a technique that increases the surface hardness of the male screw and applies a compressive residual stress to the male screw.
  • Patent Document 2 is a technique that increases the surface hardness of the round portion beneath the bolt neck by applying cold working to the round portion beneath the bolt neck and applies a compressive residual stress to the round portion beneath the bolt neck, however, is not a technique that increases the surface hardness of the male screw and applies a compressive residual stress to the male stress. Therefore, similarly to the former, improvement by the latter of the fatigue resistance of the male screw is also limited.
  • Patent Document 1 Japanese Patent Application Laid-open Publication No. 1981-53651
  • Patent Document 1 Japanese Patent Application Laid-open Publication No. 07-180714
  • the problem that the present invention is to solve lies in that improvement of the fatigue resistance of the male screw is limited for a bolt that is a conventional fastening member.
  • the present invention (the invention of claim 1 ) includes a surface hardening portion that is disposed at least on the surface of the male screw to increase a surface hardness and to provide a compressive residual stress.
  • the surface hardening portion is formed by a process in which the particles having a equal or smaller particle size of being capable of passing through a mesh with a mesh size of #150 are projected to at least the surface of the male screw.
  • the present invention includes the steps of cutting to form the male screw, and processing to provide on at least the surface of the male screw a surface hardening portion that has increased hardness and that is applied with a compressive residual stress.
  • the processing step includes a surface treatment by which the particles having a equal or smaller particle size of being capable of passing through a mesh with a mesh size of #150 are projected to at least the surface of the male screw.
  • the bolt of the present invention (the present invention of claim 1 ) has the increased surface hardness of the male screw thereof and has a compressive residual stress applied to the surface of the male screw thereof, due to the surface hardening portion provided at least on the surface of the male screw thereof. Therefore, the bolt of the present invention (the present invention of claim 1 ) enables improvement of the fatigue resistance of the male screw thereof and, therefore, the bolt is effective to be used in a portion where the male screw is subject to a repetitive stress.
  • the bolt of the present invention (the present invention of claim 2 ) has the surface hardening portion that is provided by processing of applying particles each having the particle diameter that can pass through the mesh having the mesh size of #150 or a smaller particle diameter, to at least the surface of the male screw. Therefore, the bolt of the present invention (the present invention of claim 2 ) has the increased surface hardness of the male screw thereof and has the compressive residual stress applied to the surface of the male screw thereof while no influence is given to the improvement of the fatigue resistance of the male screw due to the roughness of the surface of the male screw. As a result, the bolt of the present invention (the present invention of claim 2 ) securely enables the improvement of the fatigue resistance of the male screw.
  • the manufacturing method of the bolt of the present invention provides, using the step of processing, the surface hardening portion on the surface of the male screw of the bolt formed by the step of cutting. Therefore, due to the surface hardening portion, the surface hardness of the male screw is increased and a compressive residual stress is applied to the surface of the male screw. Therefore, the manufacturing method of a bolt of the present invention (the present invention of claim 3 ) enables improvement of the fatigue resistance of the male screw and, therefore, the method enables the manufacture of a bolt that is effective to be used in a portion that generates a repetitive stress to the male screw thereof.
  • the surface hardening portion is formed on the surface of the male screw of the bolt by processing of applying the particles each having the particle diameter that can pass through the mesh having the mesh size of #150 or a smaller particle diameter, to at least the surface of the male screw. Therefore, the manufacturing method of a bolt of the present invention (the present invention of claim 4 ) enables increase of the surface hardness of the male screw and application of the compressive residual stress to the surface of the male screw while no influence is given to the improvement of the fatigue resistance of the male screw due to the roughness of the surface of the male screw. As a result, the manufacturing method of a bolt of the present invention (the present invention of claim 4 ) enables manufacture of a bolt of which the fatigue resistance of the male screw can securely be improved.
  • FIGS. 1A and 1B are partial enlarged cross-sectional views of an embodiment of a bolt according to the present invention.
  • FIGS. 2A and 2B are a view and a chart for explaining an embodiment of a manufacturing method of a bolt according to the present invention.
  • FIG. 3 is a view for explaining a fatigue resistance validating test using a fatigue resistance validation testing apparatus.
  • FIG. 4 is a chart for explaining the result of the fatigue resistance validating test using the fatigue resistance validation testing apparatus for a conventional product and an product 1 of the present invention.
  • FIG. 5 is a chart for explaining the influence on the fatigue resistance depending on particle sizes.
  • FIG. 6 is a chart for explaining the influence on the fatigue resistance depending on the number of projections.
  • FIG. 7 is a chart for explaining the influence on the fatigue resistance depending on projection distances.
  • FIGS. 8A and 8B are views for explaining an embodiment of a manufacturing method of a nut.
  • FIG. 9 is a chart for explaining the result of a fretting fatigue test using test pieces of nuts.
  • FIG. 10 is a view for explaining a conventional bolt used as a rotor spindle bolt of a gas turbine.
  • FIG. 11 is a partial enlarged cross-sectional view of an engaging portion of screws.
  • FIG. 1A is a partial enlarged cross-sectional view of the structure of a female screw of a nut
  • FIG. 1B is a partial enlarged cross-sectional view of the structure of a male screw of a bolt according to the embodiment.
  • FIG. 2A is a view for explaining an embodiment of a processing step of a surface hardening portion of the manufacturing method of a bolt according to the embodiment and
  • FIG. 2B is a chart for explaining a condition for the processing of the surface hardening portion.
  • a reference numeral “1” denotes a bolt according to the embodiment.
  • the bolt 1 is configured by, for example, a nickel-based super alloy.
  • the bolt 1 can be a bolt that is configured by, for example, iron, low alloy steel, stainless steel, or another super alloy, in addition to the nickel-based super alloy.
  • the bolt 1 includes a head portion, a shaft portion, and a screw portion each formed by cutting processing.
  • a male screw 10 having an effective diameter d is formed by cutting processing.
  • a surface hardening portion 11 having increased surface hardness and applied with a compressive residual stress is provided.
  • the surface hardening portion 11 is formed by a processing step such as, for example, a shot blast or a shot peening.
  • a processing step such as, for example, a shot blast or a shot peening.
  • the head portion, the shaft portion, and the screw portion of the bolt 1 are configured and the male screw 10 having the effective diameter d is formed on the outer face of the screw portion.
  • the surface hardening portion 11 having increased surface hardness and applied with a compressive residual stress is provided.
  • the surface hardening portion 11 is processed under the condition shown in FIGS. 2A and 2B . That is: a bolt screw thread circumferential velocity (S) at which the male screw 10 of the bolt 1 is rotated around the shaft center thereof is 80 mm/s; a blast gun moving velocity (V) at which a blast gun 13 is moved in parallel to the shaft center of the bolt 1 is 8 mm/s; an projections distance (L) that is the distance from the blast gun 13 to the male screw 10 of the bolt 1 is 500 mm; a blast material supplying pressure (P) that is the force to apply a blast material from the blast gun 13 to the male screw 10 of the bolt 1 is 0.55 MPa; and the particle diameter of the blast material to be applied from the blast gun 13 to the male screw 10 of the bolt 1 is a particle diameter that can pass through a mesh having the mesh size of #150 (a mesh is 100 ⁇ m ⁇ 100 ⁇ m) or a smaller particle diameter.
  • S bolt screw thread circumferential velocity
  • V blast gun moving velocity
  • L
  • each of the bolt 1 according to the embodiment and the bolt 1 manufactured according to the manufacturing method of a bolt according the embodiment can be used, for example, as the rotor spindle bolt of the gas turbine shown in FIG. 10 or a stud bolt of an engine crank case. That is, each of the bolt 1 according to the embodiment and the bolt 1 manufactured according to the manufacturing method of a bolt according the embodiment is effective as a bolt to be used in a portion where the male screw 10 is subject to a repetitive stress.
  • the bolt 1 to be tested is inserted into a lateral hole 31 of a base 30 of the fatigue resistance validation testing apparatus 3 .
  • the bolt 1 is fixed on the base 30 under a predetermined tensile load by fastening a nut 2 or nuts 2 at an end or respectively ends of the bolt 1 .
  • a pushing bar 33 is inserted into a longitudinal hole 32 of the base 30 and the pushing bar 33 is pressed onto the bolt 1 .
  • a stress measuring device 34 is provided on the bolt 1 in the vicinity of a portion 35 to be tested.
  • the stress measuring device 34 is a measuring device to judge whether any crack has been generated in the portion 35 to be tested and, when the value being measured suddenly varies, this shows that a crack is generated in the portion 35 to be tested.
  • a fatigue test on the portion 35 to be tested (the thread face and the screw bottom of the bolt 1 ) of the bolt 1 is executed by applying a predetermined repetitive bending load to the bolt 1 by the pushing bar 33 .
  • the predetermined tensile load is a load that is about 2 ⁇ 3 of the load that plastic-deforms the bolt 1 .
  • the predetermined repetitive bending load is a load that is about 2 to 2.5% of the load that plastic-deforms the bolt 1 .
  • FIG. 4 The result of the fatigue resistance validating test using the fatigue resistance validation testing apparatus 3 is shown in FIG. 4 .
  • the axis of ordinate of FIG. 4 represents the number of times of the application of the predetermined repetitive bending load applied to the bolt by the pushing bar 33 .
  • a conventional product (a conventional bolt) has a crack generated in the portion to be tested when the number of times of the application of the predetermined repetitive bending load is about 6.3 ⁇ 10 6 .
  • the product 1 of the present invention (each of the bolt 1 according to the embodiment and the bolt 1 manufactured according to the manufacturing method of a bolt according to the embodiment) has no crack generated in the portion 35 to be tested even when the number of times of the application of the predetermined repetitive bending load exceeds about 1.2 ⁇ 10 7 . That is, the product 1 of the present invention has obtained the fatigue resistance thereof that is about two times as high as that of the conventional product.
  • each of the bolt 1 according to the embodiment and the bolt 1 manufactured according to the manufacturing method of a bolt according to the embodiment can obtain fatigue resistance that is more than two times as high as that of a conventional bolt and, therefore, is effective as a bolt to be used in a portion where the male screw 10 is subject to a repetitive stress such as the rotor spindle bolt of the gas turbine as shown in FIG. 10 or a stud bolt of an engine crank case.
  • the surface hardening portion 11 having increased surface hardness and applied with a compressive residual stress is provided at least on the surface of the male screw 10 by processing of applying particles (the blast material) to at least the surface of the male screw 10 .
  • the most important factor is the particle diameter of the particles (the blast material) to be applied to at least the surface of the male screw 10 .
  • objects are “to improve the hardness of” and “to apply a compressive residual stress to” at least the surface of the male screw 10 to improve the fatigue resistance thereof.
  • the “roughness” of at least the surface of the male screw 10 is varied and, thereby, the fatigue resistance of the screw bottom is significantly influenced.
  • the “improvement of the hardness of” and “application of a compressive residual stress to” at least the surface of the male screw 10 are not influenced by the magnitude of the particle diameter.
  • the “roughness” of at least the surface of the male screw 10 is influenced by the magnitude of the particle diameter.
  • the particle diameter is for the mesh size #46 (a mesh is 355 ⁇ m ⁇ 355 ⁇ m, that is, a measure of the blast material particle diameter)
  • the mesh size #80 a mesh is 180 ⁇ m ⁇ 180 ⁇ m, that is, a measure of the blast material particle diameter
  • the mesh size #100 a mesh is 150 ⁇ m ⁇ 150 ⁇ m, that is, a measure of the blast material particle diameter
  • the “surface roughness” of at least the surface of the male screw 10 is high and the fatigue resistance of the screw bottom is almost same as that of the conventional product shown in FIG. 4 .
  • the particle diameter is for the mesh size #150 (a mesh is 100 ⁇ m ⁇ 100 ⁇ m, that is a measure of the blast material particle diameter), and the mesh size #360 (a mesh is 70 ⁇ m ⁇ 70 ⁇ m, that is a measure of the blast material particle diameter)
  • the “surface roughness” of at least the surface of the male screw 10 is low and the fatigue resistance of the screw bottom almost same as that of the product 1 of the present invention shown in FIG. 4 can be obtained.
  • the male screw 10 is applied with the blast material having the particle diameter that can pass through a mesh of the mesh size #150 (a mesh is 100 ⁇ m ⁇ 100 ⁇ m) or a smaller particle diameter, preferably, the mesh size #150 (a mesh is 100 ⁇ m ⁇ 100 ⁇ m, that is, a measure of the blast material particle diameter), and the mesh size #360 (a mesh is 70 ⁇ m ⁇ 70 ⁇ m, that is, a measure of the blast material particle diameter).
  • Conditions for the processing using the blast material include the number of times of the projections of the blast material and the projection distance (L) from the blast gun to the male screw as the next important factors following the particle diameter of the blast material. Referring to FIGS. 6 and 7 , description will be given below for the influence on the fatigue resistance due to the number of times of the projections of the blast material to the male screw 10 of the bolt 1 and the projection distance (L) from the blast gun to the male screw.
  • FIG. 6 is a chart of the relation between the number of times of the projections of the blast material, and the residual stress and the surface roughness.
  • the axis of abscissa represents the number of times of the projections.
  • the axis of ordinate on the left represents the compressive residual stress.
  • the axis of ordinate on the right represents the surface roughness (Rmax) of the surface of the male screw.
  • the compressive residual stress is represented as becoming larger in the upward direction on the axis of ordinate and smaller in the downward direction on the axis of ordinate.
  • the blast material is applied to the outer surface of the male screw 10 of the bolt 1 with the bolt being rotated while the blast gun is simultaneously moved along the shaft direction.
  • the gun turns into the reverse direction when the gun reaches the end of the male screw and is moved in the reverse direction continuously applying the blast material.
  • the gun repeats this repetitive movement and, thereby, the processing of the surface of the male screw is executed.
  • the number of times of the projections represents the number of times (the frequency) the blast material is applied to one same surface.
  • FIG. 7 shows the relation between the projection distance from the blast gun to the male screw, and the residual stress and the surface roughness.
  • the axis of abscissa represents the projection distance.
  • the axes of ordinates are same as those of FIG. 6 .
  • FIG. 7 shows the result of the processing with, as the processing conditions, the number of times of the projections being fixed at four times, other conditions being selected similarly to those in FIG. 6 , and varied projection distances.
  • the policy on the reference values and the axes of ordinates is same as that of FIG. 6 .
  • the compressive residual stress is significantly insufficient for the reference value when the number of times of projections is two times, and reaches the reference value when the number of times of the projections is four.
  • the number of times of the projections is six, some increase of the compressive residual stress can be recognized.
  • the surface roughness has no significant change in the magnitude thereof when the number of times of the projections is two to four.
  • the surface roughness is somewhat increased when the number of times of the projections is six. When the number of times of the projections exceeds six, the surface roughness is drastically increased.
  • the compressive residual stress is insufficient for the reference value and the surface roughness significantly exceeds the reference value when the projection distance is 200 mm.
  • the compressive residual stress and the surface roughness both respectively satisfy the reference values thereof.
  • the projection distance is 750 mm
  • the compressive residual stress and the surface roughness both respectively are somewhat lower than the reference values thereof.
  • the compressive residual stress is remarkably lowered.
  • the compressive residual stress exceeds the reference value thereof while the variation of the surface roughness is relatively small and almost no influence associated with the increase of the surface roughness on the fatigue resistance is present.
  • the projection distance is 500 to 750 mm
  • the compressive residual stress almost reaches the reference value thereof and, even when the projection distance is increased, decrease of the compressive residual stress is relatively small. That is, though the compressive residual stress is increased when the number of times of the projections is increased, decrease of the fatigue resistance is caused because the surface roughness becomes too large when the number of times of the projections exceeds six.
  • the compressive residual stress becomes larger when the projection distance is smaller, the fatigue resistance, on the contrary, becomes lower because the surface roughness simultaneously becomes larger.
  • the projection distance exceeds 750 mm, the effect of the blast processing becomes weak and the fatigue resistance is not increased. Therefore, it is preferable to select the number of times of the projections of four to six times and the projection distance of 500 to 750 mm as the processing conditions. Under these conditions, the hardness equal to or larger than that of the base material of the bolt can be secured as the surface hardness of the surface hardening portion.
  • a rustproof nonferrous material such as alumina (Al 2 O 3 ), silicon carbide (SiC), or silica (SiO 2 ) is used as the material of the particles to be applied to at least the surface of the male screw 10 .
  • FIG. 8A is a partial enlarged cross-sectional view of the surface roughness of the male screw of the bolt and the surface roughness of the female screw of the nut.
  • FIG. 8B is a partial enlarged cross-sectional view of the structure of the female screw of the nut.
  • the reference numerals “ 2 ” denote the nut.
  • the nut 2 is configured by, for example, steel.
  • a threaded hole is configured by cutting. Inside the threaded hole, a female screw 20 is formed by cutting.
  • a surface soft coating portion 21 having hardness that is lower than that of the base material of the nut 2 is provided on the surface of the female 20 of the nut 2 .
  • the surface soft coating portion 21 is provided by, for example, Cu—Ni—In flame spray coating, cermetal W coating, silver plating, copper plating, etc. As shown in FIGS. 8A and 8B , the thickness (film thickness) T of the surface soft coating portion 21 is set to be larger than the sum of the maximum T 1 of the roughness of the surface 12 of the male screw 10 of the bolt 1 and the maximum T 2 of the roughness of the surface 22 of the female screw 20 of the nut 2 .
  • the effective diameter of the female screw 20 of the nut 2 needs to be varied. That is, for the nut 2 , the effective diameter DO of the female screw 20 (that is, the effective diameter DO of the female screw of the base material) employed when the surface soft coating portion 21 is provided needs to be set to be larger by the dimension almost same as that of the thickness T of the surface soft coating portion 21 than the effective diameter D of the female screw 20 (that is, the effective diameter D of a finished product female screw) employed when the surface soft coating portion 21 is not provided.
  • the thickness T of the surface soft coating portion 21 when the thickness T of the surface soft coating portion 21 is set to be too large, the effective diameter D 0 of the female screw of the base material becomes too large against the effective diameter D of the finished product female screw. Thereby, the screw ridge in the original size becomes too small and, therefore, the strength may be insufficient.
  • the thickness T of the surface soft coating portion 21 has the maximum thereof around the dimension (X) with which the thread ridge in the original size is not too small and, thereby, the strength is not insufficient.
  • the thickness T of the surface soft coating portion 21 is in the following range. That is, the range is T 1 +T 2 ⁇ T ⁇ (X).
  • the thickness T of the surface soft coating portion 21 differs depending on the tolerance of the screw and, for example, the thickness T is about 25 ⁇ m for the Class-II screw tolerance (for the Class-II fitting).
  • a screw hole of the nut 2 is configured and the female screw 20 is formed on the inner face of the screw hole.
  • the effective diameter D 0 of the female screw 20 is larger by the thickness T of the surface soft coating portion 21 than the effective diameter D of the finished product female screw.
  • the surface soft coating portion 21 having hardness that is lower than that of the base material of the nut 2 is provided on the surface of the female screw 20 of the nut 2 by, for example, Cu—Ni—In flame spray coating, cermetal W coating, silver plating, copper plating, etc.
  • the nut 2 shown in FIG. 1A and the nut 2 manufactured according to the manufacturing method of a nut shown in FIGS. 8A and 8B can be used as a nut to be screwed into the rotor spindle bolt of the gas turbine shown in FIG. 10 or a stud bolt of an engine crank case. That is, almost similarly to the bolt 1 according to the embodiment and the bolt 1 manufactured according to the manufacturing method of a bolt according to the embodiment, the nut 2 shown in FIG. 1A and the nut 2 manufactured according to the manufacturing method of a nut shown in FIGS. 8A and 8B are effective as nuts to be used in a portion where the engaging portion of the male screw 10 of the bolt 1 and the female screw 20 of the nut 2 is subject to a repetitive stress.
  • the axis of ordinate of FIG. 9 represents the number of times of repetition of fatigue.
  • a break occurs to a conventional product (a conventional nut).
  • a break occurs to the products 2 of the present invention (the nut 2 shown in FIG. 1A and the nut 2 manufactured according to the manufacturing method of a nut shown in FIGS. 8A and 8B that each have a surface soft coating portion 21 formed by plating).
  • the number of times of fatigue repetition has exceeded about 1.1 ⁇ 10 7 , no break occurs to products 3 of the present invention (the nut 2 shown in FIG.
  • the bolt 1 and the nut 2 are further effective as a bolt and a nut used in a portion where the engaging portion of the male screw 10 of the bolt 1 and the female screw 20 of the nut 2 is subject to a repetitive stress such as the rotor spindle bolt and the nut of the gas turbine shown in FIG. 10 .
  • a bolt according to the present invention and a manufacturing method of a bolt according to the present invention are useful as a bolt and a manufacturing method of the bolt to be used in a portion where a male screw thereof is subject to a repetitive stress.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Articles (AREA)
  • Connection Of Plates (AREA)
US12/087,603 2006-02-10 2007-01-25 Bolt and Manufacturing Method of Bolt Abandoned US20090003968A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP2006034168 2006-02-10
JP2006-034168 2006-02-10
PCT/JP2007/051148 WO2007091430A1 (fr) 2006-02-10 2007-01-25 Boulon et procede de fabrication de boulons

Related Parent Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2007/051148 A-371-Of-International WO2007091430A1 (fr) 2006-02-10 2007-01-25 Boulon et procede de fabrication de boulons

Related Child Applications (1)

Application Number Title Priority Date Filing Date
US13/178,928 Division US8607604B2 (en) 2006-02-10 2011-07-08 Bolt and manufacturing method of bolt

Publications (1)

Publication Number Publication Date
US20090003968A1 true US20090003968A1 (en) 2009-01-01

Family

ID=38345035

Family Applications (2)

Application Number Title Priority Date Filing Date
US12/087,603 Abandoned US20090003968A1 (en) 2006-02-10 2007-01-25 Bolt and Manufacturing Method of Bolt
US13/178,928 Active 2027-07-10 US8607604B2 (en) 2006-02-10 2011-07-08 Bolt and manufacturing method of bolt

Family Applications After (1)

Application Number Title Priority Date Filing Date
US13/178,928 Active 2027-07-10 US8607604B2 (en) 2006-02-10 2011-07-08 Bolt and manufacturing method of bolt

Country Status (5)

Country Link
US (2) US20090003968A1 (fr)
EP (1) EP1990552B1 (fr)
JP (2) JPWO2007091430A1 (fr)
CN (1) CN101379307A (fr)
WO (1) WO2007091430A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100166546A1 (en) * 2008-12-31 2010-07-01 Mahan Vance A Apparatuses, systems, and methods of gas turbine engine component interconnection
US8465259B2 (en) 2010-04-29 2013-06-18 Siemens Energy, Inc. Gas turbine spindle bolt structure with reduced fretting motion
US20160010481A1 (en) * 2014-07-14 2016-01-14 Siemens Energy, Inc. Gas turbine spindle bolt structure with reduced fretting fatigue
CN117889137A (zh) * 2024-03-18 2024-04-16 中国航发四川燃气涡轮研究院 一种可提高盘间螺栓抗疲劳能力的螺栓结构及其设计方法

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101780629B (zh) * 2010-04-08 2011-04-27 浙江裕泰紧固件制造有限公司 一种异形螺栓的生产工艺
CN102649218A (zh) * 2011-02-25 2012-08-29 温永林 一种手动卡紧螺栓加工工艺
US20150107072A1 (en) * 2013-10-22 2015-04-23 Kazim Ozbaysal Fatigue resistant turbine through bolt
CN105772869A (zh) * 2016-05-13 2016-07-20 贵州航太精密制造有限公司 一种高强度外螺纹的加工方法
KR101939728B1 (ko) * 2017-08-04 2019-01-17 주식회사 배성 스터드볼트 제조방법
KR102009082B1 (ko) * 2017-09-29 2019-08-08 한국서부발전 주식회사 볼트 제작 방법
TWI683967B (zh) * 2018-12-28 2020-02-01 態金材料科技股份有限公司 製造防鏽蝕自攻螺絲之方法及其製品
CN110270797B (zh) * 2019-06-27 2020-09-15 宁波嘉东工具有限公司 一种弹簧压缩器加工方法
CN116604474A (zh) * 2023-06-13 2023-08-18 上海海隆石油管材研究所 一种钻杆接头螺纹表面处理工艺

Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2263527A (en) * 1940-02-09 1941-11-18 Reed & Prince Mfg Company Fastening device and process
US2270662A (en) * 1939-01-19 1942-01-20 Anchor Hocking Glass Corp Coated steel article
US2335958A (en) * 1941-03-31 1943-12-07 Arthur L Parker Sealing and antiseize composition and article coated therewith
US3294139A (en) * 1964-06-01 1966-12-27 Elastic Stop Nut Corp Plastic patch, self-locking threaded fasteners and methods of making such fasteners
US3345452A (en) * 1964-02-27 1967-10-03 Thomas & Betts Corp Sintered powdered metal connectors
US3527729A (en) * 1964-06-22 1970-09-08 Minnesota Mining & Mfg Glare-free coating compositions of elastomeric particles in an elastomeric film-former
US4824314A (en) * 1985-02-19 1989-04-25 Northrop Corporation Composite fastener system and manufacturing method thereof
US4863330A (en) * 1987-07-15 1989-09-05 Northrop Corporation Composite fastener and method of manufacture
US5417776A (en) * 1991-07-17 1995-05-23 Daidousanso Co., Ltd. Hard austenitic stainless steel screw
US5484244A (en) * 1994-02-07 1996-01-16 Mse, Inc. Self-locking threaded fasteners
US20080019793A1 (en) * 2006-07-21 2008-01-24 Hilti Aktiengesellschaft Fastening element

Family Cites Families (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5279163A (en) 1975-12-03 1977-07-04 Nippon Steel Corp Screw joint which is excellent in fatigue characteristics
US4243821A (en) 1979-09-13 1981-01-06 Pennwalt Corporation Process for the preparation of symmetrical dicumyl peroxides
JPS616209A (ja) 1984-06-20 1986-01-11 Hikari Seikou Kk ステンレス鋼製ボルト
JP2646728B2 (ja) * 1989-02-17 1997-08-27 トヨタ自動車株式会社 高強度ボルトの製造方法
JPH04256577A (ja) * 1991-02-08 1992-09-11 Toyo Seiko Kk 静的負荷ボルトの遅れ破壊防止法
JPH0649509A (ja) * 1992-01-28 1994-02-22 Mazda Motor Corp 鉄系焼結合金製部材およびその製造方法
JPH06229409A (ja) * 1993-01-29 1994-08-16 Mazda Motor Corp 鋼製ボルトの製造方法
JPH07180714A (ja) 1993-12-24 1995-07-18 Nippon Steel Corp 疲労強度の優れたボルトの製造法
CN1060226C (zh) 1997-04-29 2001-01-03 蔡东宏 使金属锅体具有高硬度、耐蚀、不沾性的表面加工方法
JP3456636B2 (ja) * 1999-05-13 2003-10-14 新東工業株式会社 ショットピ−ニング方法
JP3436724B2 (ja) * 1999-09-27 2003-08-18 株式会社メイドー ボルトおよび該ボルトの製造方法
JP4256577B2 (ja) 1999-11-25 2009-04-22 株式会社リコー 画像形成装置
JP4437353B2 (ja) * 2000-03-30 2010-03-24 株式会社タンガロイ 被覆切削工具およびその製造方法
JP4289645B2 (ja) 2000-06-20 2009-07-01 三菱重工業株式会社 圧縮機のスピンドルボルト取付構造
JP2002036115A (ja) * 2000-07-31 2002-02-05 Sintokogio Ltd ショットピ−ニング処理方法及びその被処理品
JP3420568B2 (ja) * 2000-12-18 2003-06-23 大阪瓦斯株式会社 低熱膨張係数材料
US7438512B2 (en) * 2001-08-20 2008-10-21 Maclean-Fogg Company U-bolt assembly
US7017952B2 (en) * 2002-06-21 2006-03-28 Maclean-Fogg Company Fluid connector
JP2005187850A (ja) * 2003-12-24 2005-07-14 Sanyo Special Steel Co Ltd 高強度機械部品の製造方法
JP2005199329A (ja) * 2004-01-16 2005-07-28 Daido Steel Co Ltd βチタン合金ボルトの製造方法
JP2005207268A (ja) * 2004-01-21 2005-08-04 Isuzu Motors Ltd シリンダブロック
JP2005221038A (ja) * 2004-02-06 2005-08-18 Sumitomo Metal Ind Ltd 油井管用ネジ継手、及びその製造方法
DE602005021286D1 (de) * 2004-09-15 2010-07-01 Sumitomo Metal Ind Stahl-Rohr mit ausgezeichneter Beständigkeit gegen Abblättern auf der inneren Oberfläche

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2270662A (en) * 1939-01-19 1942-01-20 Anchor Hocking Glass Corp Coated steel article
US2263527A (en) * 1940-02-09 1941-11-18 Reed & Prince Mfg Company Fastening device and process
US2335958A (en) * 1941-03-31 1943-12-07 Arthur L Parker Sealing and antiseize composition and article coated therewith
US3345452A (en) * 1964-02-27 1967-10-03 Thomas & Betts Corp Sintered powdered metal connectors
US3294139A (en) * 1964-06-01 1966-12-27 Elastic Stop Nut Corp Plastic patch, self-locking threaded fasteners and methods of making such fasteners
US3527729A (en) * 1964-06-22 1970-09-08 Minnesota Mining & Mfg Glare-free coating compositions of elastomeric particles in an elastomeric film-former
US4824314A (en) * 1985-02-19 1989-04-25 Northrop Corporation Composite fastener system and manufacturing method thereof
US4863330A (en) * 1987-07-15 1989-09-05 Northrop Corporation Composite fastener and method of manufacture
US5417776A (en) * 1991-07-17 1995-05-23 Daidousanso Co., Ltd. Hard austenitic stainless steel screw
US5484244A (en) * 1994-02-07 1996-01-16 Mse, Inc. Self-locking threaded fasteners
US20080019793A1 (en) * 2006-07-21 2008-01-24 Hilti Aktiengesellschaft Fastening element

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100166546A1 (en) * 2008-12-31 2010-07-01 Mahan Vance A Apparatuses, systems, and methods of gas turbine engine component interconnection
US8465259B2 (en) 2010-04-29 2013-06-18 Siemens Energy, Inc. Gas turbine spindle bolt structure with reduced fretting motion
US20160010481A1 (en) * 2014-07-14 2016-01-14 Siemens Energy, Inc. Gas turbine spindle bolt structure with reduced fretting fatigue
US9598961B2 (en) * 2014-07-14 2017-03-21 Siemens Energy, Inc. Gas turbine spindle bolt structure with reduced fretting fatigue
CN117889137A (zh) * 2024-03-18 2024-04-16 中国航发四川燃气涡轮研究院 一种可提高盘间螺栓抗疲劳能力的螺栓结构及其设计方法

Also Published As

Publication number Publication date
EP1990552B1 (fr) 2013-10-02
JPWO2007091430A1 (ja) 2009-07-02
US8607604B2 (en) 2013-12-17
CN101379307A (zh) 2009-03-04
JP5404847B2 (ja) 2014-02-05
WO2007091430A1 (fr) 2007-08-16
EP1990552A1 (fr) 2008-11-12
EP1990552A4 (fr) 2012-06-27
JP2012176491A (ja) 2012-09-13
US20110268533A1 (en) 2011-11-03

Similar Documents

Publication Publication Date Title
US8607604B2 (en) Bolt and manufacturing method of bolt
RU2128109C1 (ru) Способ упрочняющего накатывания детали
EP1938926B1 (fr) Procédé pour la détermination de paramètres de brunissage initiaux
Wang et al. Influence of ultrasonic surface rolling process and shot peening on fretting fatigue performance of Ti-6Al-4V
Huang et al. On the role of thermal exposure on the stress controlled fatigue behaviour of a high strength titanium–aluminum alloy
TWI387687B (zh) 用於將以低塑性變形能力之材料製作之螺帽加以鎖定之方法
JP2001079766A (ja) ショットピーニング用投射材
Gronostajski et al. The use of 3D scanning methods to evaluate the hybrid layer used in forging tools in order to improve their durability
Kelbassa et al. Laser cladding as a repair technique for BLISKs out of titanium and nickel base alloys used in aero engines
JP2007211932A (ja) ねじ締結部材、および、ねじ締結部材の製造方法
Byczkowska et al. Analysis of the impact of double shot peening on the value of roughness parameter and distribution of stresses in the RSA 501 alloy
Yu et al. Fracture failure of bolts assembled in tuning-wheel of a marine diesel engine
CN108362417B (zh) 一种轧辊表面等离子熔覆钴基合金残余应力计算方法
Stephens et al. Influence of cold rolling threads before or after heat treatment on the fatigue resistance of high strength coarse thread bolts for multiple preload conditions
Bradley et al. Influence of cold rolling threads before or after heat treatment on the fatigue resistance of high strength fine thread bolts for multiple preload conditions
Vinh et al. Study the Effect of Chrome Coating Thickness to Fatigue Strength of the Axle-Shaped Machine Parts
Horn et al. Influence of cold rolling threads before or after heat treatment on high strength bolts for different fatigue preload conditions
Hazra et al. Failure of Locking Wires of an Aeroengine Component: Attributed Primarily to Over-twisting and Secondarily to Engine Vibration and Improper Material Selection
Kadhim et al. Mechanical properties of burnished steel AISI 1008
RU2484914C1 (ru) СПОСОБ ИЗГОТОВЛЕНИЯ КРЕПЕЖНЫХ ИЗДЕЛИЙ ИЗ ДВУХФАЗНЫХ (α+β) ТИТАНОВЫХ СПЛАВОВ
Eccles Fatigue failure of bolts
Shirakawa et al. An Effect of Bearing Surface Angle at Bolt Head on the Nut Factor and Contact Area Ratio in Tightening Bolted Joints
Nadar Fatigue testing of scratched flapper valve steel
JPS62235539A (ja) ボルトの保守管理方法
Glienke et al. Experimental Investigations of the Mechanical-Technological Properties and Fatigue Strength of Stainless Steel Bolting Assemblies

Legal Events

Date Code Title Description
AS Assignment

Owner name: MITSUBISHI HEAVY INDUSTRIES, LTD., JAPAN

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:TEZUKA, NORIKAZU;HIROKAWA, KAZUHARU;IHARA, KEISUKE;AND OTHERS;REEL/FRAME:021271/0315

Effective date: 20080623

STCB Information on status: application discontinuation

Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION