WO2017061445A1 - Method and device for manufacturing hardened steel, steel for hardening, and hardened steel - Google Patents

Method and device for manufacturing hardened steel, steel for hardening, and hardened steel Download PDF

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Publication number
WO2017061445A1
WO2017061445A1 PCT/JP2016/079553 JP2016079553W WO2017061445A1 WO 2017061445 A1 WO2017061445 A1 WO 2017061445A1 JP 2016079553 W JP2016079553 W JP 2016079553W WO 2017061445 A1 WO2017061445 A1 WO 2017061445A1
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Prior art keywords
steel material
steel
heating
quenching
locally
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PCT/JP2016/079553
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French (fr)
Japanese (ja)
Inventor
嘉明 中澤
直明 嶋田
雄也 金井田
茂貴 山下
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新日鐵住金株式会社
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Publication of WO2017061445A1 publication Critical patent/WO2017061445A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D7/00—Bending rods, profiles, or tubes
    • B21D7/16—Auxiliary equipment, e.g. for heating or cooling of bends
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/34—Methods of heating
    • C21D1/42—Induction heating
    • 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
    • C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
    • 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
    • C21D9/50—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for welded joints
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

Definitions

  • the present disclosure relates to a method and an apparatus for manufacturing a hardened steel material, a steel material for hardening, and a hardened steel material.
  • the present inventors are researching and developing a three-dimensional hot bending and quenching (3DQ) technique in which an arbitrary portion of a steel material is heated, bent into an arbitrary shape, and strengthened by quenching.
  • 3DQ is a technique suitably used for manufacturing vehicle structural materials and the like.
  • the structural material manufactured by 3DQ has the features of light weight and high strength. There is a feature that a mold is not necessary for manufacturing a structural material or the like by 3DQ.
  • the heating device and the cooling device are arranged close to each other.
  • a bending moment in an arbitrary direction is given to a high temperature portion generated in the steel material between the heating device and the cooling device while passing the steel material in the order of the heating device and the cooling device.
  • any part of steel can be bent into any shape and processed into a hardened member.
  • the bending moment applying means is not particularly limited.
  • a bending moment applying means a movable roller die arranged on the downstream side in the steel material feed direction of the cooling device as in International Publication Number WO2006 / 093006, and a steel material end on the downstream side in the steel material feed direction as in International Publication Number WO2010 / 050460
  • Patent Document 1 and Patent Document 3 disclose that twist processing is possible with 3DQ.
  • International publication number WO2010 / 084898 discloses a torsion member according to 3DQ.
  • the main purpose of the present disclosure is to provide a technology capable of preventing or suppressing fatigue failure of a member manufactured by a technique such as 3DQ, which is deformed by bending, such as hot, and then quenched.
  • a steel material for quenching having a martensite structure or a bainite structure for producing a quenched steel material by induction heating and quenching is provided.
  • a steel material for quenching that is a welded steel pipe having a martensite structure or a bainite structure is provided.
  • a steel material for quenching manufactured by heating a steel material to Ac3 transformation point + 10 ° C. or higher and 1100 ° C. or lower and then cooling.
  • a steel material for quenching manufactured by heating a steel material of a welded steel pipe to an Ac3 transformation point + 10 ° C. or higher and 1100 ° C. or lower and then cooling.
  • FIG. 1 is a schematic configuration diagram for explaining a hardened steel manufacturing apparatus according to a preferred embodiment of the present disclosure.
  • FIG. 2 is an SEM photograph of a ferrite-pearlite structure tube that was not heat-treated before 3DQ.
  • FIG. 3 is an SEM photograph of an element tube having a martensite structure manufactured by heat treatment before 3DQ.
  • FIG. 4 is an SEM photograph of an elementary tube having a bainite structure manufactured by heat treatment before 3DQ.
  • FIG. 5 is a diagram showing a comparison of hardness when the 3DQ heating temperature is 850 ° C.
  • FIG. 6A is a photograph of a surface crack observed by a microscope when there is no heat treatment before 3DQ and the structure before 3DQ uses a ferrite-pearlite tube and the 3DQ heating temperature is 900 ° C.
  • FIG. 6B is a photograph of a surface crack observed by a microscope when heat treatment before 3DQ is performed and a raw tube whose structure before 3DQ is martensite is used and the 3DQ heating temperature is 900 ° C.
  • the fatigue fracture surface of a member manufactured by 3DQ is a grain boundary fracture surface, and Cu exists on the fracture surface.
  • fatigue failure often occurs outside the bending of a bent member. From this, the present inventors considered the reason why fatigue fracture occurs as follows.
  • 3DQ is the following method. While feeding the steel material, the induction heating device locally heats the steel material to the Ac3 transformation point or higher, and the steel material is rapidly quenched by the cooling device on the downstream side in the steel feed direction from the induction heating device. In the steel material between the induction heating device and the cooling device, a high temperature portion having a temperature equal to or higher than the local Ac3 transformation point is generated. By applying a bending moment to the high-temperature part, the steel material is hot-bent and is quenched and fixed in shape by cooling with a cooling device.
  • the steel material subjected to fatigue failure was manufactured by rapidly heating a steel material having a ferrite-pearlite structure to 1000 ° C. or higher (for example, a heating rate of 800 ° C./sec) with an induction heating device.
  • the reason for rapid heating is that the processing accuracy is better if the region softened at a high temperature of the steel material is narrowed.
  • the Ac3 transformation point of the steel material is approximately 800 to 900 ° C. depending on its composition.
  • the distribution of carbides in the steel material of the original material is not uniform, so C is not uniformly dispersed and the hardness after quenching is not stable. In order to uniformly disperse C in order to stabilize the hardness after quenching, heating at 1000 ° C. or higher is necessary in the case of rapid heating.
  • the heating temperature is lowered to avoid melting of Cu, the hardness after quenching will be hindered. If the heating rate is lowered to disperse C even at a low temperature at which the melting of Cu is avoided, the processing accuracy is hindered. That is, it is not possible to solve all of the hardness, processing accuracy, and fatigue fracture avoidance after quenching only by changing the hot bending quenching conditions.
  • the inventors of the present invention do not need to raise the temperature to a high temperature by rapid heating if the steel material to be subjected to 3DQ is not a ferrite-pearlite structure steel material but a steel material in which C is uniformly dispersed before rapid heating. We thought that all of hardness after hardening, processing accuracy and fatigue fracture avoidance could be achieved.
  • the steel material in which C is uniformly dispersed is a steel material having a martensite structure or a bainite structure.
  • the embodiment of the present disclosure is based on the above knowledge, and according to one aspect of the embodiment, (1) A step of locally inductively heating a steel material having a martensite structure or a bainite structure to a temperature not lower than the Ac3 transformation point and not higher than 950 ° C. while continuously moving the position of the portion to be locally induction heated; A step of locally continuously deforming a locally induction-heated portion of the steel material of the martensite structure or bainite structure; And a step of continuously quenching a locally continuously deformed portion of the steel material having the martensite structure or the bainite structure.
  • the method further includes the step of manufacturing a steel material.
  • a method for producing a quenched steel material according to (7) preferably, The chemical composition is mass%, Ti: 0.001% or more and 0.05% or less, Nb: 0.001% or more and 0.05% or less, V: 0.02% to 0.5%, Cr: 0.02% to 0.5%, Mo: 0.02 to 0.5%, It contains one or more elements selected from the group consisting of Cu: 0.02% to 1.0% and Ni: 0.02% to 1.0%.
  • (10) A method for producing a quenched steel material according to any one of (2) to (4), wherein the steel material is preferably set to Ac3 transformation point + 10 ° C. or higher and 1100 ° C. or lower for 0.3 second or longer and 10 minutes. Heat less than.
  • the time from the arrival to the cooling for quenching is 0.2 second or more and 1.0 second or less.
  • a first heating device for heating the steel material for heating the steel material; A first cooling device that cools the heated steel material; A second heating device for locally inductively heating the steel material; A deforming force applying device for applying a deforming force locally to the locally heated portion of the steel material; A second cooling device for cooling and quenching a locally deformed portion of the steel material; A moving device for continuously moving the steel material, The moving device is a moving device that moves the steel material relative to the first heating device, the first cooling device, the second heating device, and the second cooling device; The first heating device, the first cooling device, the second heating device, and the second cooling device are arranged in this order in the relative movement direction of the steel material.
  • a device for manufacturing a quenched steel material according to (13), preferably, A control device for controlling the moving device, the first heating device, the first cooling device, the second heating device, the second cooling device, and the deformation force applying device;
  • the control device causes the moving device to continuously move the steel material relative to the first heating device, the first cooling device, the second heating device, and the second cooling device in this order.
  • the steel material is heated to Ac3 transformation point + 10 ° C. or higher and 1100 ° C. or lower by the first heating device while being moved, and the heated steel material is cooled by the first cooling device, and the second heating device.
  • the steel material is induction-heated locally continuously from the Ac3 transformation point to 950 ° C., and the deformation force is applied to the locally heated portion of the steel material by the deformation-force applying device. Then, the moving device and the first heating device are configured so that the steel material is continuously deformed and the locally deformed portion of the steel material is continuously cooled and quenched by the second cooling device.
  • the moving device, the second heating device, and the second cooling device are controlled so that the time until the time is 0.2 second or more and 1.0 second or less.
  • a steel material for quenching with a martensite structure or a bainite structure for producing a quenched steel material after induction heating is provided.
  • a steel material for quenching which is a welded steel pipe having a martensite structure or a bainite structure is provided.
  • a steel material for quenching manufactured by heating a steel material to Ac3 transformation point + 10 ° C. or higher and 1100 ° C. or lower and then cooling the steel is provided.
  • a steel material for quenching produced by heating a steel material of a welded steel pipe to an Ac3 transformation point + 10 ° C. to 1100 ° C. and then cooling the steel material is provided.
  • the steel material having the ferrite-pearlite structure includes a bainite structure of 30% by volume or less.
  • the steel material for quenching according to any one of (18) to (28) is locally moved to a temperature not lower than the Ac3 transformation point and not higher than 950 ° C. while continuously moving the position of the portion to be locally induction heated.
  • the three-dimensional hot bending and quenching (3DQ) technique in which an arbitrary portion of the steel material is heated, bent into an arbitrary shape, and strengthened by quenching has been described, but the present disclosure is preferable.
  • the embodiment includes not only the case where the heated high temperature portion of the steel material is bent, but also the case where the heated high temperature portion of the steel material is deformed, such as when twisting or shearing. Therefore, hereinafter, a technique for performing deformation such as bending, twisting, and shearing in the hot state and then performing quenching is referred to as a hot deformation and quenching technique.
  • the hot bending and quenching (3DQ) technology is used when the only hot deformation is bending, or when the hot deformation includes bending, such as twisting while hot. That's it.
  • the heating is preferably performed by induction heating.
  • induction heating In order to increase the processing accuracy, it is better to narrow the region softened at a high temperature of the steel material, and for that purpose, a higher heating rate is better.
  • the steel material In order to narrow the region softened at high temperature, the steel material is locally heated by induction heating, and the position of the portion to be locally induction heated is continuously moved while the cooling position is also adjusted to the induction heating. To move.
  • the heating temperature is preferably from Ac3 transformation point to 950 ° C.
  • the heating temperature exceeds 950 ° C.
  • surface cracking occurs in the processed steel material, which is not preferable. Since surface cracks are the starting point of fatigue fracture, fatigue fracture can be prevented or suppressed by avoiding surface cracks.
  • the melting point of Cu is 1085 ° C. However, since Cu mixed on the steel material surface is not pure Cu, the melting point is lower than 1085 ° C., and the heating temperature for hot deformation quenching that can avoid fatigue failure is preferably 950 ° C. or less that can avoid surface cracking.
  • the locally induction-heated portion is locally and continuously deformed.
  • the deformation is preferably at least one of bending, twisting and shearing.
  • the locally continuously deformed part of the steel having a martensite or bainite structure is continuously quenched, and martensitic transformation is performed.
  • a hardened steel material is manufactured.
  • the time from when the locally induction-heated portion of the steel material of the martensite structure or bainite structure reaches the Ac3 transformation point until the quenching cooling is performed is 0.2 in order to achieve stable austenite. It is preferable that it is 1.0 second or less from a viewpoint of productivity more than second.
  • the structure of the steel material before hot deformation quenching to a martensite structure or a bainite structure.
  • the steel structure before hot deformation quenching is martensitic or bainite
  • the steel is heated to Ac3 + 10 ° C. or higher and 1100 ° C. or lower, and then cooled to obtain a steel material having a martensitic or bainite structure.
  • the cooling rate is controlled even at a heating temperature of 720 ° C. or more and Ac3 point or less and the second phase is a structure in which a bainite or martensite structure is mixed, the hardenability is higher than that in which heat treatment before hot deformation quenching is not performed.
  • the temperature of the hot deformation quenching is not sufficiently lowered, it is preferable to perform heating at Ac3 + 10 ° C. or higher in the embodiment.
  • the heating temperature of the hot deformation quenching exceeds 1100 ° C., the austenite grain size becomes coarse, the quenching stability at the time of martensitic transformation is deteriorated, and the toughness is lowered. It is preferable to set it to below °C.
  • the heating temperature and heating time vary depending on the heating mode, and in the case of rapid heating, it is preferable to heat to a higher temperature to achieve complete austenite. On the other hand, in the case of low-speed heating, heating at a lower temperature is possible than in the case of rapid heating.
  • the heating time is preferably at least 0.3 seconds or more in the temperature range of Ac3 + 10 ° C. to 1100 ° C. in order to achieve stable austenite.
  • An upper limit is not specified, but heating for an excessively long time is preferably less than 10 minutes in order to cause scale generation and productivity reduction.
  • the cooling and temperature conditions after heating may be controlled according to the target tissue.
  • it may be cooled to room temperature after heating, and may be set while looking at the CCT (continuous cooling transformation diagram) of the material.
  • the steel material having a martensite structure or a bainite structure is preferably a martensite structure or a bainite structure: 80% by volume or more, and the balance: retained austenite, ferrite, and carbide.
  • carbides are easily dissolved when austenitizing, so that the Ac3 transformation point can be lowered. As a result, the heating temperature at the time of hot deformation quenching can be lowered.
  • a steel material having a martensite structure or a bainite structure As a material for producing a steel material having a martensite structure or a bainite structure, a steel material having a ferrite-pearlite structure is preferably used.
  • the hot deformation quenching technique is a technique in which deformation such as bending, twisting, and shearing is performed hot, followed by quenching, so that a mold or the like is not required.
  • a steel material having a steel pipe shape can be used as a steel material having a martensite structure or a bainite structure as a material for hot deformation quenching.
  • a steel material having a martensitic structure or a bainite structure of a welded steel pipe is preferably used as a material for hot deformation quenching.
  • a welded steel pipe by welding a steel sheet having a martensite structure or a bainite structure.
  • a steel material having a martensite structure or a bainite structure has high strength and low ductility, so that it is inferior in pipe forming workability and cracks during welding. Therefore, it is preferable to manufacture a steel material having a martensite structure or a bainite structure by manufacturing a welded steel pipe in advance and heating the steel material of the welded steel pipe to an Ac3 transformation point + 10 ° C. to 1100 ° C. and then cooling.
  • the welded steel pipe manufactured in advance is preferably a welded steel pipe having a ferrite-pearlite structure manufactured by welding steel sheets having a ferrite-pearlite structure.
  • a steel material having a ferrite-pearlite structure has high strength and low ductility, and therefore has excellent tube forming workability. Therefore, a welded steel pipe is not manufactured by welding a steel sheet having a martensite structure or a bainite structure, but a welded steel pipe is manufactured by previously welding a steel sheet having a ferrite-pearlite structure, and the welded steel pipe is heat-treated to obtain a martensite. It is easier to manufacture a welded steel pipe having a site structure or a bainite structure.
  • the structure after hot rolling is generally ferrite-pearlite and is not easily broken, but part of the structure may be bainite depending on the conditions of hot rolling. If the bainite structure is 30% by volume or less, the steel material having a ferrite-pearlite structure may contain a bainite structure of 30% by volume or less because it does not break.
  • the hardened steel material manufacturing apparatus 10 includes a pre-heat treatment unit 11, a hot deformation quenching unit 12, a moving device 21, a guide 40, and a deformation force applying device 71.
  • the pre-heat treatment unit 11 includes a heating device 32 and a cooling device 34.
  • the heating device 32 is disposed on the upstream side in the steel material moving direction 2, and the cooling device 34 is disposed on the downstream side in the steel material moving direction 2.
  • the heating device 32 includes a heating unit 31 and a power source 35 that supplies power to the heating unit 31.
  • a heating unit 31 for example, high frequency induction heating or resistance heating is preferably used.
  • high frequency induction heating a high frequency induction coil is suitably used for the heating unit 31, and an induction current is generated in the steel material 1 to heat the steel material 1.
  • resistance heating a heater is preferably used for the heating unit 31.
  • the cooling device 34 includes a cooling unit 33 and a cooling medium supply unit 37 that supplies the cooling unit 33 with a cooling medium.
  • a cooling medium for cooling by the cooling device 34, for example, water cooling or air cooling is preferably used.
  • water cooling for example, water is suitably used as the cooling medium.
  • air cooling gas is preferably used as the cooling medium.
  • the cooling unit 33 a nozzle that blows the cooling medium supplied from the cooling medium supply unit 37 onto the steel material 1 is preferably used.
  • the hot deformation quenching unit 12 includes a high frequency induction heating device 52 and a water cooling device 54.
  • the high frequency induction heating device 52 is arranged on the upstream side in the steel material moving direction 2, and the cooling device 54 is arranged on the downstream side in the steel material moving direction 2.
  • the high frequency induction heating device 52 includes an induction heating coil 51 and a high frequency power supply 55 that supplies high frequency power to the induction heating coil 51.
  • High frequency power is supplied from the high frequency power supply 55 to the induction heating coil 51, and an induction current is locally generated in the portion 61 of the steel material 1 inside the induction heating coil 51 to locally induction heat the portion 61 of the steel material 1.
  • the cooling device 54 includes a nozzle 53 and a cooling water supply unit 57 that supplies cooling water to the nozzle 53.
  • the cooling water supplied from the cooling water supply unit 57 is sprayed onto the steel material 1 by the nozzle 53, and the heated steel material 1 is rapidly cooled to quench the steel material 1.
  • the deforming force applying device 71 holds the downstream portion of the steel material moving direction 2 from the nozzle 53 of the steel material 1 by the holding portion 72 of the deforming force applying device 71.
  • a chuck is preferably used as the holding unit 72.
  • a manipulator is preferably used as the deforming force applying device 71.
  • a movable roller die is also preferably used.
  • the hot deformation and quenching portion 12 functions as a hot bending and quenching (3DQ) portion.
  • the guide 40 is provided between the cooling unit 33 of the pre-heat treatment unit 11 and the induction heating coil 51 of the hot deformation quenching unit 12.
  • the moving device 21 holds the upstream portion of the steel material 1 in the steel material moving direction 2 with the holding portion 23 of the moving device 21, and continues the long steel material 1 along its longitudinal direction (steel material moving direction 2). To move.
  • the heating unit 31, the cooling unit 33, the induction heating coil 51, and the nozzle 53 are arranged in this order in the steel material moving direction 2. Since the moving device 21 continuously moves the steel material 1 along the steel material moving direction 2, the steel material 1 is moved in the order of the heating unit 31, the cooling unit 33, the induction heating coil 51, and the nozzle 53. Further, by the continuous movement of the steel material 1 along the steel material movement direction 2, the deformation force is locally applied by the part 61 of the steel material 1 that is locally induction heated by the induction heating coil 51 and the deformation force applying device 71. The high temperature portion 63 of the steel material 1 and the portion 65 that is rapidly cooled by being sprayed with cooling water by the nozzle 53 also move continuously along the steel material movement direction 2.
  • the movement with respect to the heating part 31, the cooling part 33, the induction heating coil 51, and the nozzle 53 of the steel material 1 by the moving apparatus 21 is relative, and the heating part 31, the cooling part 33, the induction heating coil 51, and the nozzle 53 are relative. May be moved and the steel material 1 may be moved, and the steel material 1 may be fixed and the heating part 31, the cooling part 33, the induction heating coil 51, and the nozzle 53 may be moved.
  • an electric servo cylinder or a manipulator is preferably used as the moving device 21.
  • a chuck is preferably used as the holding unit 23.
  • the moving device 21, the heating device 32, the cooling device 34, the high frequency induction heating device 52, the water cooling device 54, and the deformation force applying device 71 are connected to the control device 100 and controlled by the control device 100.
  • the heat treatment and hot deformation quenching described above and below are performed by control of the moving device 21, the heating device 32, the cooling device 34, the high frequency induction heating device 52, the water cooling device 54, and the deformation force applying device 71 by the control device 100. Is called.
  • the structure of the steel material 1 becomes martensite or bainite by the pre-heat treatment part 11.
  • the steel material 1 having a martensite structure or a bainite structure is subjected to a hot deformation quenching process by the hot deformation quenching part 12 to produce a hardened steel material.
  • a steel material having a ferrite-pearlite structure is preferably used.
  • a steel pipe having a closed cross-sectional shape is preferably used, and as the steel pipe, a welded steel pipe is preferable. Used.
  • a steel material having a martensite structure or a bainite structure was produced in-line with a hardened steel material production apparatus 10 in which the pre-heat treatment part 11 and the hot deformation quenching part 12 were integrated, and subsequently hot deformation quenching treatment was performed.
  • a hardened steel material may be manufactured, but a heat treatment device including a pre-heat treatment unit 11 is provided separately from the hot deformation and quenching unit 12, and a steel material having a martensite structure or a bainite structure is manufactured using the heat treatment device including the pre-heat treatment unit 11 in advance. Then, you may manufacture the hardened steel material by which the hot deformation hardening process was carried out with the apparatus provided with the hot deformation hardening part 12 after that.
  • a steel material having a martensite structure or a bainite structure is manufactured by the high frequency induction heating device 52 and the water cooling device 54 without using the deformation force applying device 71.
  • a hardened steel material that has been subjected to hot deformation quenching with the high-frequency induction heating device 52, the water cooling device 54, and the deformable force applying device 71 may be manufactured using the deformable force applying device 71.
  • the steel material that is a material for producing the steel material of the martensite structure or bainite structure of the embodiment is preferably, Chemical composition is mass%, C: 0.12% to 0.60%, Si: 0.001% to 2.0%, Mn: 0.5% to 3.0%, P: 0.05% or less, S: 0.01% or less, sol. Al: 0.001% to 1.0%, N: 0.01% or less, B: 0.01% or less, The balance: Fe and impurities.
  • the chemical composition is in mass% instead of part of Fe, Ti: 0.001% or more and 0.05% or less, Nb: 0.001% or more and 0.05% or less, V: 0.02% to 0.5%, Cr: 0.02% to 0.5%, Mo: 0.02 to 0.5%, Cu: 0.02% to 1.0% and Ni: 0.02% to 1.0%, You may contain 1 type, or 2 or more types of elements chosen from the group which consists of.
  • C is mass% and is preferably controlled in the range of 0.12 to 0.60%.
  • the processing method in the embodiment is a manufacturing method using so-called quenching, in which heat treatment and processing history are controlled to obtain a high-strength and processed product that has undergone structural transformation from an austenite phase to a hard phase such as martensite. Since the strength after quenching of the steel sheet is mainly determined by the C content that controls the hardness of the martensite phase, the C content is determined according to the required strength. In order to secure the target strength of 1200 MPa or more in the embodiment, the C content is preferably 0.12% or more. In order to stably obtain higher strength, the content is more preferably over 0.20%. When the C content exceeds 0.60%, the toughness after quenching deteriorates and the risk of causing brittle fracture increases. Therefore, the upper limit of the C content is preferably 0.60%, and more preferably 0.50% or less.
  • Si is preferably mass%, and is preferably controlled in the range of 0.001% to 2.0%.
  • Si is an element that has the effect of increasing the strength after quenching without degrading the ductility or improving the ductility in order to suppress the formation of carbides in the cooling process from the austenite phase to the low temperature transformation phase. is there. If the Si content is less than 0.001%, it is difficult to obtain the above effect. Therefore, the Si content is preferably 0.001% or more. Note that when the Si content is 0.05% or more, the ductility is further improved. Therefore, the Si content is more preferably 0.05% or more. On the other hand, if the Si content exceeds 2.0%, the effects of the above action are saturated and disadvantageous economically, and the surface properties are significantly deteriorated. Therefore, the Si content is preferably 2.0% or less. More preferably, it is 1.5% or less.
  • Mn is preferably mass%, and is preferably controlled within the range of 0.5% to 3.0%.
  • Mn is an extremely effective element for enhancing the hardenability of the steel and ensuring the strength after quenching stably.
  • the Mn content is preferably 0.5% or more.
  • the Mn content is 1.0% or more, it is possible to ensure a tensile strength of 1350 MPa or more as the strength after quenching. For this reason, it is more preferable that the Mn content is 1.0% or more.
  • the Mn content is preferably 3.0% or less. From the viewpoint of alloy cost and the like, the Mn content is more preferably 2.5% or less.
  • P is preferably controlled to be 0.05% or less by mass%.
  • P is an impurity inevitably contained in steel, but it may be positively incorporated because it has the effect of increasing strength by solid solution strengthening.
  • the P content exceeds 0.05%, the resistance weldability between the member of the present invention and the other member is significantly deteriorated.
  • the risk of brittle fracture increases when the strength is increased to 2500 MPa or more. Therefore, the P content is preferably 0.05% or less.
  • the P content is more preferably 0.02% or less. In order to obtain the above action more reliably, the P content is preferably set to 0.003% or more.
  • S it is preferable to control S to 0.01% or less by mass%.
  • S is an impurity inevitably contained in the steel, and is combined with Mn and Ti to produce sulfide and precipitate. If the amount of this precipitate increases excessively, the interface between the precipitate and the main phase may become the starting point of fracture, so the lower the content, the better. If the S content exceeds 0.01%, the adverse effect becomes significant. Therefore, the S content is preferably 0.01% or less. More preferably, it is 0.003% or less, More preferably, it is 0.0015% or less.
  • Al is preferably controlled in the range of 0.001% to 1.0% or less.
  • Al is an element having an action of deoxidizing steel to make the steel material sound, and is also an element having an action of improving the yield of carbonitride forming elements such as Ti. sol.
  • the Al content is preferably 0.001% or more. More preferably, it is 0.015% or more.
  • sol. If the Al content exceeds 1.0%, the weldability is significantly lowered and the oxide inclusions are increased, so that the surface properties are remarkably deteriorated. Therefore, sol.
  • the Al content is preferably 1.0% or less. More preferably, it is 0.080% or less.
  • N is an impurity inevitably contained in the steel, and is preferably as low as possible from the viewpoint of weldability. If the N content exceeds 0.01%, the weldability is significantly reduced. Therefore, the N content is preferably 0.01% or less. More preferably, it is 0.006% or less.
  • B is preferably controlled to be 0.01% or less by mass.
  • B is an element having an effect of increasing low temperature toughness. Therefore, B may be contained. However, if the content exceeds 0.01%, the hot workability deteriorates and hot rolling becomes difficult. Therefore, the B content is preferably 0.01% or less. In addition, in order to acquire the effect by the said action more reliably, it is preferable to make B content 0.0003% or more.
  • the present inventors investigated the influence of the structure control before 3DQ on the surface crack and hardenability after 3DQ using 3DQ blanks having the chemical composition shown in Table 1.
  • the structure of the 3DQ base tube was ferrite-pearlite to ensure the workability when forming from steel plate.
  • This element tube has not been heat-treated before 3DQ.
  • the raw tube having martensite as the structure before 3DQ is heated to 1000 ° C., which is the same as the heating temperature at the time of 3DQ, by high-frequency induction heating, and heated at a heating rate of 800 ° C./sec by high-frequency induction heating. It was manufactured by a heat treatment that was rapidly cooled to room temperature with air and water (temperature decrease rate: 1000 ° C./sec).
  • the bainite-structured tube was heated to 1000 ° C. at a heating rate of 800 ° C./sec by high-frequency induction heating, and then cooled to 450 ° C. with Ar gas (temperature-decreasing rate 50 ° C./sec). After holding for 240 seconds, the substrate was manufactured by heat treatment by cooling to room temperature with Ar gas (temperature decrease rate: 50 ° C./sec).
  • SEM photograph of a ferrite-pearlite structure unprocessed 3DQ tube, a martensitic structure 3DQ preheated, and a bainite structure preheated 3DQ heat treated tube Are shown in FIGS. 2, 3, and 4, respectively. The magnification is 2000 times.
  • each tube was heated at 800 ° C to 1050 ° C by high-frequency induction heating, and the bending radius was 95 mm. 3D hot bending quenching (3DQ) was performed. Thereafter, the outer surface of each processed product was observed with a microscope and analyzed for surface cracks. Furthermore, the bending center section was cut out, and the presence or absence of quenching was evaluated by measuring the Vickers hardness with a load of 1 kgf in the cross section direction of the long axis side of the section.
  • FIG. 5 shows a comparison of hardness when the 3DQ heating temperature is 850 ° C.
  • the target hardness Vickers hardness 470
  • the target hardness can be obtained even at 850 ° C.
  • bainite has a higher hardness than martensite in the structure of the raw tube before 3DQ.
  • FIG. 6A and FIG. 6B show a comparison of microscopic surface crack observation photographs with and without heat treatment before 3DQ when the 3DQ heating temperature is 900 ° C.
  • FIG. The magnification is 175 times.
  • 6A shows the case where there is no heat treatment before 3DQ and the structure before 3DQ uses a ferrite-pearlite tube
  • FIG. 6B shows the tube where the heat treatment before 3DQ is performed and the structure before 3DQ is martensite. Is used.
  • FIG. 6B shows the tube where the heat treatment before 3DQ is performed and the structure before 3DQ is martensite.
  • Table 2 summarizes the evaluation results. The presence or absence of cracks was confirmed with a microscope (magnification of 175 times). When the Vickers hardness was 470 or more, it was determined that there was quenching.
  • the structure of the controlled element tube enables austenite transformation in a short time when heated in the 3DQ process, and is stable. Hardenability can be realized. That is, there is no surface cracking even under severe bending conditions, and stable hardenability can be ensured.

Abstract

The present invention includes continuously shifting the position of a section, which is to be locally induction-heated, of steel having a martensite structure or a bainite structure while locally induction-heating the section at a temperature between the Ac3 transformation point and 950 degrees Celsius inclusive, locally and continuously deforming the locally induction-heated section of the steel having the martensite structure or the bainite structure, and continuously hardening the locally and continuously deformed section of the steel having the martensite structure or the bainite structure.

Description

焼入れ鋼材の製造方法および製造装置、焼入れ用鋼材ならびに焼入れ鋼材Method and apparatus for manufacturing hardened steel, steel for hardening, and hardened steel
　本開示は、焼入れ鋼材の製造方法および製造装置、焼入れ用鋼材ならびに焼入れ鋼材に関する。 The present disclosure relates to a method and an apparatus for manufacturing a hardened steel material, a steel material for hardening, and a hardened steel material.
　鋼材の任意の箇所を、加熱し、任意の形状に曲げ、焼入れにより高強度化する３次元熱間曲げ焼入れ(３ＤＱ: 3Dimensional Hot Bending and Quench)技術を本発明者達は研究
開発している。３ＤＱは車両の構造材等の製造に好適に用いられる技術である。３ＤＱにより製造される構造材には軽量かつ高強度という特長がある。３ＤＱによる構造材等の製造には金型が不要であるという特長がある。 The present inventors are researching and developing a three-dimensional hot bending and quenching (3DQ) technique in which an arbitrary portion of a steel material is heated, bent into an arbitrary shape, and strengthened by quenching. 3DQ is a technique suitably used for manufacturing vehicle structural materials and the like. The structural material manufactured by 3DQ has the features of light weight and high strength. There is a feature that a mold is not necessary for manufacturing a structural material or the like by 3DQ.
　３ＤＱ装置では、加熱装置と冷却装置が近接して配置される。３ＤＱ装置を使用した鋼材の加工では、鋼材を加熱装置と冷却装置の順に通過させながら、加熱装置と冷却装置の間の鋼材に生じる高温部に任意の方向の曲げモーメントを与える。３ＤＱ技術によって、鋼材の任意の箇所が任意の形状に曲げられ、焼入れされた部材に加工できる。 In the 3DQ device, the heating device and the cooling device are arranged close to each other. In the processing of a steel material using a 3DQ device, a bending moment in an arbitrary direction is given to a high temperature portion generated in the steel material between the heating device and the cooling device while passing the steel material in the order of the heating device and the cooling device. With 3DQ technology, any part of steel can be bent into any shape and processed into a hardened member.
　曲げモーメント付与手段は、特に限定されない。曲げモーメント付与手段としては、国際公開番号ＷＯ２００６／０９３００６のように冷却装置の鋼材送り方向下流側に配置された可動ローラーダイス、国際公開番号ＷＯ２０１０／０５０４６０のように鋼材送り方向下流側の鋼材端部に取り付けられたチャックとマニピュレータ、国際公開番号ＷＯ２０１１／００７８１０のように鋼材送り方向上流側の鋼材端部に取り付けられたチャックとマニピュレータが例示される。 The bending moment applying means is not particularly limited. As a bending moment applying means, a movable roller die arranged on the downstream side in the steel material feed direction of the cooling device as in International Publication Number WO2006 / 093006, and a steel material end on the downstream side in the steel material feed direction as in International Publication Number WO2010 / 050460 The chuck and manipulator attached to the steel material, and the chuck and manipulator attached to the steel material end on the upstream side in the steel material feed direction as in International Publication No. WO2011 / 007810.
　３ＤＱでは、曲げ加工のみならず、ねじり加工も可能である。特許文献１と特許文献３には３ＤＱでねじり加工が可能であることが開示されている。国際公開番号ＷＯ２０１０／０８４８９８には３ＤＱによるねじり部材が開示されている。 3DQ allows not only bending but also twisting. Patent Document 1 and Patent Document 3 disclose that twist processing is possible with 3DQ. International publication number WO2010 / 084898 discloses a torsion member according to 3DQ.
開示の概要Summary of disclosure
　本開示の主な目的は、３ＤＱ等の、熱間で曲げ等の変形を行いその後焼入れを行う技術で製造された部材の疲労破壊を防止または抑制できる技術を提供することにある。 The main purpose of the present disclosure is to provide a technology capable of preventing or suppressing fatigue failure of a member manufactured by a technique such as 3DQ, which is deformed by bending, such as hot, and then quenched.
　本開示の一態様によれば、
　マルテンサイト組織またはベイナイト組織の鋼材を、局所的に誘導加熱する部分の位置を連続して移動させつつ、Ａｃ３変態点以上９５０℃以下の温度に局所的に誘導加熱する工程と、
　前記マルテンサイト組織またはベイナイト組織の鋼材の局所的に誘導加熱された部分を局所的に連続して変形する工程と、
　前記マルテンサイト組織またはベイナイト組織の鋼材の局所的に連続して変形された部分を連続して焼入れする工程と、を備える焼入れ鋼材の製造方法が提供される。 According to one aspect of the present disclosure,
A step of locally inductively heating a steel material having a martensite structure or a bainite structure to a temperature not lower than the Ac3 transformation point and not higher than 950 ° C. while continuously moving the position of the portion to be locally induction heated;
A step of locally continuously deforming a locally induction-heated portion of the steel material of the martensite structure or bainite structure;
And a step of continuously quenching a locally continuously deformed portion of the steel material having the martensite structure or the bainite structure.
　本開示の他の態様によれば、
　鋼材を加熱する第１の加熱装置と、
　加熱された前記鋼材を冷却する第１の冷却装置と、
　前記鋼材を局所的に誘導加熱する第２の加熱装置と、
　前記鋼材の局所的に誘導加熱された部分に局所的に変形力を付与する変形力付与装置と、
　前記鋼材の局所的に変形力を付与された部分を冷却して焼入れする第２の冷却装置と、
　前記鋼材を連続して移動させる移動装置と、を備え、
　前記移動装置は、前記鋼材を、前記第１の加熱装置、前記第１の冷却装置、前記第２の加熱装置および前記第２の冷却装置に対して相対的に移動させる移動装置であり、
　前記第１の加熱装置、前記第１の冷却装置、前記第２の加熱装置および前記第２の冷却装置は前記鋼材の相対的な移動方向にこの順に配置されている、焼入れ鋼材の製造装置が提供される。 According to another aspect of the present disclosure,
A first heating device for heating the steel material;
A first cooling device that cools the heated steel material;
A second heating device for locally inductively heating the steel material;
A deforming force applying device for applying a deforming force locally to the locally heated portion of the steel material;
A second cooling device for cooling and quenching a locally deformed portion of the steel material;
A moving device for continuously moving the steel material,
The moving device is a moving device that moves the steel material relative to the first heating device, the first cooling device, the second heating device, and the second cooling device;
The first heating device, the first cooling device, the second heating device, and the second cooling device are arranged in this order in the relative movement direction of the steel material. Provided.
　本開示のさらに他の態様によれば、誘導加熱後焼入れして焼入れ鋼材を製造するためのマルテンサイト組織あるいはベイナイト組織の焼入れ用鋼材が提供される。 According to still another aspect of the present disclosure, a steel material for quenching having a martensite structure or a bainite structure for producing a quenched steel material by induction heating and quenching is provided.
　本開示のさらに他の態様によれば、マルテンサイト組織あるいはベイナイト組織の溶接鋼管である焼入れ用鋼材が提供される。 According to still another aspect of the present disclosure, a steel material for quenching that is a welded steel pipe having a martensite structure or a bainite structure is provided.
　本開示のさらに他の態様によれば、鋼材を、Ａｃ３変態点＋１０℃以上１１００℃以下に加熱しその後冷却して製造した焼入れ用鋼材が提供される。 According to still another aspect of the present disclosure, there is provided a steel material for quenching manufactured by heating a steel material to Ac3 transformation point + 10 ° C. or higher and 1100 ° C. or lower and then cooling.
　本開示のさらに他の態様によれば、溶接鋼管の鋼材を、Ａｃ３変態点＋１０℃以上１１００℃以下に加熱しその後冷却して製造した焼入れ用鋼材が提供される。 According to still another aspect of the present disclosure, there is provided a steel material for quenching manufactured by heating a steel material of a welded steel pipe to an Ac3 transformation point + 10 ° C. or higher and 1100 ° C. or lower and then cooling.
図１は、本開示の好ましい実施の形態の焼入れ鋼材の製造装置を説明するための概略構成図である。FIG. 1 is a schematic configuration diagram for explaining a hardened steel manufacturing apparatus according to a preferred embodiment of the present disclosure. 図２は、３ＤＱ前の熱処理を行わなかったフェライト－パーライト組織の素管のＳＥＭ写真である。FIG. 2 is an SEM photograph of a ferrite-pearlite structure tube that was not heat-treated before 3DQ. 図３は、３ＤＱ前の熱処理を行なって製造したマルテンサイト組織を有する素管のＳＥＭ写真である。FIG. 3 is an SEM photograph of an element tube having a martensite structure manufactured by heat treatment before 3DQ. 図４は、３ＤＱ前の熱処理を行なって製造したベイナイト組織を有する素管のＳＥＭ写真である。FIG. 4 is an SEM photograph of an elementary tube having a bainite structure manufactured by heat treatment before 3DQ. 図５は、３ＤＱ加熱温度８５０℃の場合の硬度の比較を示す図である。FIG. 5 is a diagram showing a comparison of hardness when the 3DQ heating temperature is 850 ° C. 図６Ａは、３ＤＱ前の熱処理がなく３ＤＱ前の組織がフェライト－パーライトの素管を使用し、３ＤＱ加熱温度９００℃の場合のマイクロスコープによる表面割れ観察写真である。FIG. 6A is a photograph of a surface crack observed by a microscope when there is no heat treatment before 3DQ and the structure before 3DQ uses a ferrite-pearlite tube and the 3DQ heating temperature is 900 ° C. 図６Ｂは、３ＤＱ前の熱処理を行い、３ＤＱ前の組織をマルテンサイトとした素管を使用し、３ＤＱ加熱温度９００℃の場合のマイクロスコープによる表面割れ観察写真である。FIG. 6B is a photograph of a surface crack observed by a microscope when heat treatment before 3DQ is performed and a raw tube whose structure before 3DQ is martensite is used and the 3DQ heating temperature is 900 ° C.
　３ＤＱで製造された部材を疲労試験すると、１５０万回程度負荷をかけると疲労破壊することがある。疲労破壊した破面にはＣｕの介在が認められ、Ｃｕが疲労破壊に影響していると考えられる。３ＤＱに供せられる鋼材には故意にＣｕを付着させることは無く、Ｃｕはどこからか混入したものと考えられる。 When a member manufactured with 3DQ is subjected to a fatigue test, fatigue failure may occur if a load is applied about 1.5 million times. It is considered that Cu intervenes in the fractured surface after fatigue failure, and Cu influences fatigue failure. There is no intentional adhesion of Cu to the steel material used for 3DQ, and it is thought that Cu was mixed from somewhere.
　３ＤＱで製造された部材の疲労破壊した破面は粒界破面であり、破面にはＣｕが存在する。また、疲労破壊は曲げられた部材の曲げの外側で発生することが多い。このことから本発明者達は、疲労破壊の発生する理由を次のように考えた。 The fatigue fracture surface of a member manufactured by 3DQ is a grain boundary fracture surface, and Cu exists on the fracture surface. In addition, fatigue failure often occurs outside the bending of a bent member. From this, the present inventors considered the reason why fatigue fracture occurs as follows.
　３ＤＱは、次のような方法である。鋼材を送りながら、誘導加熱装置でＡｃ３変態点以上まで鋼材を局所的に加熱し、誘導加熱装置から鋼材の送り方向下流側において冷却装置で鋼材を速やかに焼入れする。誘導加熱装置と冷却装置の間の鋼材には局所的なＡｃ３変態点以上の温度の高温部が生じる。この高温部に曲げモーメントを与えることで鋼材を熱間曲げし、冷却装置による冷却により焼入れと形状の固定を行う。 3DQ is the following method. While feeding the steel material, the induction heating device locally heats the steel material to the Ac3 transformation point or higher, and the steel material is rapidly quenched by the cooling device on the downstream side in the steel feed direction from the induction heating device. In the steel material between the induction heating device and the cooling device, a high temperature portion having a temperature equal to or higher than the local Ac3 transformation point is generated. By applying a bending moment to the high-temperature part, the steel material is hot-bent and is quenched and fixed in shape by cooling with a cooling device.
　鋼材表面にＣｕが混入すると誘導加熱によりＣｕが溶融し鋼材表面から鋼材の結晶粒界に溶け込む。Ｃｕが溶け込み結晶粒界が弱くなった鋼材に曲げモーメントが与えられると結晶粒界に沿って微細な亀裂が生じる。微細な亀裂を抱えたまま鋼材に繰り返し負荷が与えられると微細な亀裂が起点になり、疲労破壊が生じる。 When Cu enters the steel surface, it is melted by induction heating and melts from the steel surface into the grain boundaries of the steel. When a bending moment is applied to a steel material in which Cu has melted and the crystal grain boundary has become weak, fine cracks are formed along the crystal grain boundary. When a load is repeatedly applied to a steel material with a fine crack, the fine crack becomes the starting point and fatigue failure occurs.
　この仮説によれば、Ｃｕが溶融し、鋼材表面から鋼材の結晶粒界に溶け込まなければ疲労破壊を防止または抑制できる。従って、誘導加熱装置による加熱をＣｕが溶融しない温度範囲に抑えることができれば疲労破壊を防止または抑制できると発明者達は考えた。 According to this hypothesis, fatigue fracture can be prevented or suppressed if Cu is melted and does not melt from the steel surface into the crystal grain boundaries of the steel. Accordingly, the inventors have thought that fatigue failure can be prevented or suppressed if heating by the induction heating device can be suppressed to a temperature range in which Cu does not melt.
　疲労破壊した鋼材は、フェライト－パーライト組織の鋼材を誘導加熱装置で１０００℃以上に急速加熱（例えば、昇温速度８００℃／ｓｅｃ）して製造したものであった。急速加熱するのは鋼材の高温で軟化した領域を狭くした方が、加工精度が良好であるからである。鋼材のＡｃ３変態点はその組成にもよるがおおよそ８００～９００℃である。急速加熱した場合、元の素材の鋼材中の炭化物の分布が均一でないためＣが均一に分散せず、焼入れした後の硬度が安定しない。焼入れした後の硬度を安定させるべく、Ｃを均一に分散させるには急速加熱する場合１０００℃以上の加熱が必要である。 The steel material subjected to fatigue failure was manufactured by rapidly heating a steel material having a ferrite-pearlite structure to 1000 ° C. or higher (for example, a heating rate of 800 ° C./sec) with an induction heating device. The reason for rapid heating is that the processing accuracy is better if the region softened at a high temperature of the steel material is narrowed. The Ac3 transformation point of the steel material is approximately 800 to 900 ° C. depending on its composition. When rapidly heated, the distribution of carbides in the steel material of the original material is not uniform, so C is not uniformly dispersed and the hardness after quenching is not stable. In order to uniformly disperse C in order to stabilize the hardness after quenching, heating at 1000 ° C. or higher is necessary in the case of rapid heating.
　Ｃｕの溶融を避けるべく加熱温度を下げると、焼入れ後の硬度に支障をきたす。Ｃｕの溶融が避けられる低い温度でもＣを分散させるべく加熱速度を下げると、加工精度に支障をきたす。つまり、熱間曲げ焼入れの条件を変更しただけでは焼入れ後の硬度と加工精度と疲労破壊回避の全てを解決することはできない。 If the heating temperature is lowered to avoid melting of Cu, the hardness after quenching will be hindered. If the heating rate is lowered to disperse C even at a low temperature at which the melting of Cu is avoided, the processing accuracy is hindered. That is, it is not possible to solve all of the hardness, processing accuracy, and fatigue fracture avoidance after quenching only by changing the hot bending quenching conditions.
　本発明者達は３ＤＱに供する鋼材が、フェライト－パーライト組織の鋼材ではなく、急速加熱される前からＣが均一に分散している鋼材であれば、急速加熱で高温まで昇温する必要がなく、焼入れ後の硬度と加工精度と疲労破壊回避の全てを達成できると考えた。 The inventors of the present invention do not need to raise the temperature to a high temperature by rapid heating if the steel material to be subjected to 3DQ is not a ferrite-pearlite structure steel material but a steel material in which C is uniformly dispersed before rapid heating. We thought that all of hardness after hardening, processing accuracy and fatigue fracture avoidance could be achieved.
　Ｃが均一に分散した鋼材とは、マルテンサイト組織あるいはベイナイト組織の鋼材である。 The steel material in which C is uniformly dispersed is a steel material having a martensite structure or a bainite structure.
　従って、３ＤＱ用の鋼材としてマルテンサイト組織あるいはベイナイト組織の鋼材を用いれば、焼入れ後の硬度と加工精度と疲労破壊回避の全てを達成できると考えられる。 Therefore, it is considered that if a steel material having a martensite structure or a bainite structure is used as the steel material for 3DQ, all of the hardness, processing accuracy, and fatigue fracture avoidance after quenching can be achieved.
　本開示の実施の形態は、上記知見に基づくものであり、実施の形態の一態様によれば、
（１）マルテンサイト組織またはベイナイト組織の鋼材を、局所的に誘導加熱する部分の位置を連続して移動させつつ、Ａｃ３変態点以上９５０℃以下の温度に局所的に誘導加熱する工程と、
　前記マルテンサイト組織またはベイナイト組織の鋼材の局所的に誘導加熱された部分を局所的に連続して変形する工程と、
　前記マルテンサイト組織またはベイナイト組織の鋼材の局所的に連続して変形された部分を連続して焼入れする工程と、を備える焼入れ鋼材の製造方法が提供される。 The embodiment of the present disclosure is based on the above knowledge, and according to one aspect of the embodiment,
(1) A step of locally inductively heating a steel material having a martensite structure or a bainite structure to a temperature not lower than the Ac3 transformation point and not higher than 950 ° C. while continuously moving the position of the portion to be locally induction heated;
A step of locally continuously deforming a locally induction-heated portion of the steel material of the martensite structure or bainite structure;
And a step of continuously quenching a locally continuously deformed portion of the steel material having the martensite structure or the bainite structure.
（２）（１）の焼入れ鋼材の製造方法であって、好ましくは、鋼材を、Ａｃ３変態点＋１０℃以上１１００℃以下に加熱しその後冷却して、前記マルテンサイト組織あるいはベイナイト組織の鋼材を製造する工程をさらに備える。 (2) A method for producing a quenched steel material according to (1), wherein the steel material is preferably heated to an Ac3 transformation point + 10 ° C. to 1100 ° C. and then cooled to produce the steel material having the martensite structure or bainite structure. The process of carrying out is further provided.
（３）（１）の焼入れ鋼材の製造方法であって、好ましくは、溶接鋼管の鋼材を、Ａｃ３変態点＋１０℃以上１１００℃以下に加熱しその後冷却して、前記マルテンサイト組織あるいはベイナイト組織の鋼材を製造する工程をさらに備える。 (3) A method for producing a hardened steel material according to (1), wherein the steel material of the welded steel pipe is preferably heated to an Ac3 transformation point + 10 ° C. or higher and 1100 ° C. or lower and then cooled to obtain the martensitic structure or bainite structure. The method further includes the step of manufacturing a steel material.
（４）（２）または（３）の焼入れ鋼材の製造方法であって、好ましくは、前記鋼材は、フェライト－パーライト組織の鋼材である。 (4) A method for producing a quenched steel material according to (2) or (3), wherein the steel material is preferably a steel material having a ferrite-pearlite structure.
（５）（１）から（４）までのいずれかの焼入れ鋼材の製造方法であって、好ましくは、前記マルテンサイト組織またはベイナイト組織の鋼材は溶接鋼管である。 (5) A method for producing a hardened steel material according to any one of (1) to (4), wherein the steel material having the martensite structure or the bainite structure is preferably a welded steel pipe.
（６）（１）から（５）までのいずれかの焼入れ鋼材の製造方法であって、好ましくは、前記マルテンサイト組織またはベイナイト組織の鋼材は、マルテンサイト組織またはベイナイト組織：８０体積％以上、残部：残留オーステナイト、フェライトおよび炭化物である。 (6) The method for producing a quenched steel material according to any one of (1) to (5), wherein the martensite structure or bainite structure steel is preferably a martensite structure or bainite structure: 80% by volume or more, The balance: residual austenite, ferrite and carbide.
（７）（２）から（４）までのいずれかの焼入れ鋼材の製造方法であって、好ましくは、前記マルテンサイト組織またはベイナイト組織を製造する前の鋼材は、
　化学組成が、質量％で、
　Ｃ：０．１２％以上０．６０％以下、
　Ｓｉ：０．００１％以上２．０％以下、
　Ｍｎ：０．５％以上３．０％以下、
　Ｐ：０．０５％以下、
　Ｓ：０．０１％以下、
　ｓｏｌ．Ａｌ：０．００１％以上１．０％以下、
　Ｎ：０．０１％以下、
　Ｂ：０．０１％以下、
　残部：鉄および不純物
である。 (7) A method for producing a quenched steel material according to any one of (2) to (4), wherein the steel material before producing the martensite structure or bainite structure is preferably
Chemical composition is mass%,
C: 0.12% to 0.60%,
Si: 0.001% to 2.0%,
Mn: 0.5% to 3.0%,
P: 0.05% or less,
S: 0.01% or less,
sol. Al: 0.001% to 1.0%,
N: 0.01% or less,
B: 0.01% or less,
The balance: iron and impurities.
（８）（７）の焼入れ鋼材の製造方法であって、好ましくは、
　前記化学組成が、質量％で、
　Ｔｉ：０．００１％以上０．０５％以下、
　Ｎｂ：０．００１％以上０．０５％以下、
　Ｖ　：０．０２％以上０．５％以下、
　Ｃｒ：０．０２％以上０．５％以下、
　Ｍｏ：０．０２以上０．５％以下、
　Ｃｕ：０．０２％以上１．０％以下および
　Ｎｉ：０．０２％以上１．０％以下、からなる群から選択された１種または２種以上の元素を含有する。 (8) A method for producing a quenched steel material according to (7), preferably,
The chemical composition is mass%,
Ti: 0.001% or more and 0.05% or less,
Nb: 0.001% or more and 0.05% or less,
V: 0.02% to 0.5%,
Cr: 0.02% to 0.5%,
Mo: 0.02 to 0.5%,
It contains one or more elements selected from the group consisting of Cu: 0.02% to 1.0% and Ni: 0.02% to 1.0%.
（９）（４）の焼入れ鋼材の製造方法であって、好ましくは、前記フェライト－パーライト組織の鋼材は、３０体積％以下のベイナイト組織を含む。 (9) The method for producing a hardened steel material according to (4), wherein the steel material having a ferrite-pearlite structure preferably includes 30% by volume or less of a bainite structure.
（１０）（２）から（４）までのいずれかの焼入れ鋼材の製造方法であって、好ましくは、前記鋼材を、Ａｃ３変態点＋１０℃以上１１００℃以下に、０．３秒以上、１０分未満加熱する。 (10) A method for producing a quenched steel material according to any one of (2) to (4), wherein the steel material is preferably set to Ac3 transformation point + 10 ° C. or higher and 1100 ° C. or lower for 0.3 second or longer and 10 minutes. Heat less than.
（１１）（１）から（１０）までのいずれかの焼入れ鋼材の製造方法であって、好ましくは、前記マルテンサイト組織またはベイナイト組織の鋼材の局所的に誘導加熱される部分がＡｃ３変態点に到達してから焼入れ用の冷却が行われるまでの時間が０．２秒以上１．０秒以下である。 (11) A method for producing a quenched steel material according to any one of (1) to (10), wherein a locally induction-heated portion of the steel material of the martensite structure or bainite structure is preferably at the Ac3 transformation point. The time from the arrival to the cooling for quenching is 0.2 second or more and 1.0 second or less.
（１２）（１）から（１１）までのいずれかの焼入れ鋼材の製造方法であって、好ましくは、前記変形は、曲げ、捩り、せん断の少なくとも一つである。 (12) The method for producing a hardened steel material according to any one of (1) to (11), wherein the deformation is preferably at least one of bending, twisting, and shearing.
　実施の形態の他の態様によれば、
（１３）鋼材を加熱する第１の加熱装置と、
　加熱された前記鋼材を冷却する第１の冷却装置と、
　前記鋼材を局所的に誘導加熱する第２の加熱装置と、
　前記鋼材の局所的に誘導加熱された部分に局所的に変形力を付与する変形力付与装置と、
　前記鋼材の局所的に変形力を付与された部分を冷却して焼入れする第２の冷却装置と、
　前記鋼材を連続して移動させる移動装置と、を備え、
　前記移動装置は、前記鋼材を、前記第１の加熱装置、前記第１の冷却装置、前記第２の加熱装置および前記第２の冷却装置に対して相対的に移動させる移動装置であり、
　前記第１の加熱装置、前記第１の冷却装置、前記第２の加熱装置および前記第２の冷却装置は前記鋼材の相対的な移動方向にこの順に配置されている、焼入れ鋼材の製造装置が提供される。 According to another aspect of the embodiment,
(13) a first heating device for heating the steel material;
A first cooling device that cools the heated steel material;
A second heating device for locally inductively heating the steel material;
A deforming force applying device for applying a deforming force locally to the locally heated portion of the steel material;
A second cooling device for cooling and quenching a locally deformed portion of the steel material;
A moving device for continuously moving the steel material,
The moving device is a moving device that moves the steel material relative to the first heating device, the first cooling device, the second heating device, and the second cooling device;
The first heating device, the first cooling device, the second heating device, and the second cooling device are arranged in this order in the relative movement direction of the steel material. Provided.
（１４）（１３）の焼入れ鋼材の製造装置であって、好ましくは、
　前記移動装置、前記第１の加熱装置、前記第１の冷却装置、前記第２の加熱装置、前記第２の冷却装置および前記変形力付与装置を制御する制御装置、をさらに備え、
　前記制御装置は、前記移動装置により前記鋼材を、前記第１の加熱装置、前記第１の冷却装置、前記第２の加熱装置および前記第２の冷却装置に対してこの順で連続的に相対的に移動させながら、前記第１の加熱装置により前記鋼材をＡｃ３変態点＋１０℃以上１１００℃以下に加熱し、前記加熱した鋼材を前記第１の冷却装置により冷却し、前記第２の加熱装置により前記鋼材をＡｃ３変態点以上９５０℃以下に局所的に連続して誘導加熱し、前記鋼材の局所的に誘導加熱された部分に前記変形力付与装置により変形力を局所的に連続的に付与して前記鋼材を連続して変形し、前記第２の冷却装置により前記鋼材の局所的に変形された部分を連続して冷却して焼入れするように、前記移動装置、前記第１の加熱装置、前記第１の冷却装置、前記第２の加熱装置、前記第２の冷却装置および前記変形力付与装置を制御する。 (14) A device for manufacturing a quenched steel material according to (13), preferably,
A control device for controlling the moving device, the first heating device, the first cooling device, the second heating device, the second cooling device, and the deformation force applying device;
The control device causes the moving device to continuously move the steel material relative to the first heating device, the first cooling device, the second heating device, and the second cooling device in this order. The steel material is heated to Ac3 transformation point + 10 ° C. or higher and 1100 ° C. or lower by the first heating device while being moved, and the heated steel material is cooled by the first cooling device, and the second heating device. The steel material is induction-heated locally continuously from the Ac3 transformation point to 950 ° C., and the deformation force is applied to the locally heated portion of the steel material by the deformation-force applying device. Then, the moving device and the first heating device are configured so that the steel material is continuously deformed and the locally deformed portion of the steel material is continuously cooled and quenched by the second cooling device. The first cooling device, Serial second heating device and controls the second cooling device and the deforming force applying device.
（１５）（１４）の焼入れ鋼材の製造装置であって、好ましくは、前記制御装置は、前記鋼材を、Ａｃ３変態点＋１０℃以上１１００℃以下に、０．３秒以上、１０分未満加熱するように、前記移動装置、前記第１の加熱装置および前記第１の冷却装置を制御する。 (15) The apparatus for manufacturing a quenched steel material according to (14), wherein the control device preferably heats the steel material to Ac3 transformation point + 10 ° C. or higher and 1100 ° C. or lower for 0.3 second or longer and less than 10 minutes. In this manner, the moving device, the first heating device, and the first cooling device are controlled.
（１６）（１４）または（１５）の焼入れ鋼材の製造装置であって、好ましくは、前記鋼材の局所的に誘導加熱される部分がＡｃ３変態点に到達してから焼入れ用の冷却が行われるまでの時間が０．２秒以上１．０秒以下であるように前記移動装置、前記第２の加熱装置および前記第２の冷却装置を制御する。 (16) The apparatus for manufacturing a quenched steel material according to (14) or (15), preferably, the quenching cooling is performed after the locally induction-heated portion of the steel material reaches the Ac3 transformation point. The moving device, the second heating device, and the second cooling device are controlled so that the time until the time is 0.2 second or more and 1.0 second or less.
（１７）（１３）から（１６）までのいずれかの焼入れ鋼材の製造装置であって、好ましくは、前記変形は、曲げ、捩り、せん断の少なくとも一つである。 (17) The apparatus for producing a hardened steel material according to any one of (13) to (16), wherein the deformation is preferably at least one of bending, twisting, and shearing.
　実施の形態のさらに他の態様によれば、
（１８）誘導加熱後焼入れして焼入れ鋼材を製造するためのマルテンサイト組織あるいはベイナイト組織の焼入れ用鋼材が提供される。 According to yet another aspect of the embodiment,
(18) A steel material for quenching with a martensite structure or a bainite structure for producing a quenched steel material after induction heating is provided.
（１９）（１８）の焼入れ用鋼材であって、好ましくは、前記マルテンサイト組織あるいはベイナイト組織の焼入れ用鋼材は、溶接鋼管である。 (19) The steel material for quenching according to (18), wherein the steel material for quenching with the martensite structure or the bainite structure is a welded steel pipe.
　実施の形態のさらに他の態様によれば、
（２０）マルテンサイト組織あるいはベイナイト組織の溶接鋼管である焼入れ用鋼材が提供される。 According to yet another aspect of the embodiment,
(20) A steel material for quenching which is a welded steel pipe having a martensite structure or a bainite structure is provided.
　実施の形態のさらに他の態様によれば、
（２１）鋼材を、Ａｃ３変態点＋１０℃以上１１００℃以下に加熱しその後冷却して製造した焼入れ用鋼材が提供される。 According to yet another aspect of the embodiment,
(21) A steel material for quenching manufactured by heating a steel material to Ac3 transformation point + 10 ° C. or higher and 1100 ° C. or lower and then cooling the steel is provided.
　実施の形態のさらに他の態様によれば、
（２２）溶接鋼管の鋼材を、Ａｃ３変態点＋１０℃以上１１００℃以下に加熱しその後冷却して製造した焼入れ用鋼材が提供される。 According to yet another aspect of the embodiment,
(22) A steel material for quenching produced by heating a steel material of a welded steel pipe to an Ac3 transformation point + 10 ° C. to 1100 ° C. and then cooling the steel material is provided.
（２３）（２１）または（２２）の焼入れ用鋼材であって、好ましくは、前記鋼材は、フェライト－パーライト組織の鋼材である。 (23) The steel material for quenching according to (21) or (22), wherein the steel material is preferably a steel material having a ferrite-pearlite structure.
（２４）（１８）から（２０）までのいずれかの焼入れ用鋼材であって、好ましくは、
　前記マルテンサイト組織またはベイナイト組織の鋼材は、
　マルテンサイト組織またはベイナイト組織：８０体積％以上、
　残部：残留オーステナイト、フェライトおよび炭化物である。 (24) A steel material for quenching according to any one of (18) to (20), preferably,
The steel material of the martensite structure or bainite structure,
Martensite structure or bainite structure: 80% by volume or more,
The balance: residual austenite, ferrite and carbide.
（２５）（２１）から（２３）までのいずれかの焼入れ用鋼材であって、好ましくは、
　前記鋼材は、
　化学組成が、質量％で、
　Ｃ：０．１２％以上０．６０％以下、
　Ｓｉ：０．００１％以上２．０％以下、
　Ｍｎ：０．５％以上３．０％以下、
　Ｐ：０．０５％以下、
　Ｓ：０．０１％以下、
　ｓｏｌ．Ａｌ：０．００１％以上１．０％以下、
　Ｎ：０．０１％以下、
　Ｂ：０．０１％以下、
　残部：鉄および不純物
である。 (25) A steel material for quenching according to any one of (21) to (23), preferably,
The steel material is
Chemical composition is mass%,
C: 0.12% to 0.60%,
Si: 0.001% to 2.0%,
Mn: 0.5% to 3.0%,
P: 0.05% or less,
S: 0.01% or less,
sol. Al: 0.001% to 1.0%,
N: 0.01% or less,
B: 0.01% or less,
The balance: iron and impurities.
（２６）（２５）の焼入れ用鋼材であって、好ましくは、
　前記化学組成が、質量％で、
　Ｔｉ：０．００１％以上０．０５％以下、
　Ｎｂ：０．００１％以上０．０５％以下、
　Ｖ　：０．０２％以上０．５％以下、
　Ｃｒ：０．０２％以上０．５％以下、
　Ｍｏ：０．０２以上０．５％以下、
　Ｃｕ：０．０２％以上１．０％以下および
　Ｎｉ：０．０２％以上１．０％以下、
からなる群から選択された１種または２種以上の元素を含有する。 (26) A steel material for quenching according to (25), preferably,
The chemical composition is mass%,
Ti: 0.001% or more and 0.05% or less,
Nb: 0.001% or more and 0.05% or less,
V: 0.02% to 0.5%,
Cr: 0.02% to 0.5%,
Mo: 0.02 to 0.5%,
Cu: 0.02% to 1.0% and Ni: 0.02% to 1.0%,
1 type or 2 or more types of elements selected from the group which consists of.
（２７）（２３）の焼入れ用鋼材であって、好ましくは、前記フェライト－パーライト組織の鋼材は、３０体積％以下のベイナイト組織を含む。 (27) In the steel material for quenching according to (23), preferably, the steel material having the ferrite-pearlite structure includes a bainite structure of 30% by volume or less.
（２８）（２１）から（２３）までのいずれかの焼入れ用鋼材であって、好ましくは、前記鋼材を、Ａｃ３変態点＋１０℃以上１１００℃以下に、０．３秒以上、１０分未満加熱する。 (28) The steel material for quenching according to any one of (21) to (23), wherein the steel material is preferably heated to Ac3 transformation point + 10 ° C. or higher and 1100 ° C. or lower for 0.3 second or longer and less than 10 minutes. To do.
　実施の形態のさらに他の態様によれば、
（２９）（１８）から（２８）までのいずれかの焼入れ用鋼材を、局所的に誘導加熱する部分の位置を連続して移動させつつ、Ａｃ３変態点以上９５０℃以下の温度に局所的に誘導加熱し、前記鋼材の局所的に誘導加熱された部分を局所的に連続して変形し、前記鋼材の局所的に連続して変形された部分を連続して焼入れして製造した焼入れ鋼材が提供される。 According to yet another aspect of the embodiment,
(29) The steel material for quenching according to any one of (18) to (28) is locally moved to a temperature not lower than the Ac3 transformation point and not higher than 950 ° C. while continuously moving the position of the portion to be locally induction heated. A quenched steel material produced by induction heating, locally locally deforming a portion of the steel material that is locally induction heated, and continuously quenching a locally continuously deformed portion of the steel material. Provided.
　以下、実施の形態についてさらに詳細に説明する。 Hereinafter, the embodiment will be described in more detail.
　上記では、鋼材の任意の箇所を、加熱し、任意の形状に曲げ、焼入れにより高強度化する３次元熱間曲げ焼入れ(３ＤＱ: 3Dimensional Hot Bending and Quench)技術について
述べたが、本開示の好ましい実施の形態は、鋼材の加熱した高温部分を曲げる場合のみならず、捩る場合やせん断変形する場合等、鋼材の加熱した高温部分を変形する場合も含む。従って、以下では、熱間で曲げ、捩り、せん断等の変形を行いその後焼入れを行う技術を、熱間変形焼入れ技術という。熱間変形焼入れ技術のなかで、熱間での変形が曲げのみである場合や、熱間で曲げながら捩る等、熱間での変形に曲げが含まれる場合を熱間曲げ焼入れ(３ＤＱ）技術という。 In the above description, the three-dimensional hot bending and quenching (3DQ) technique in which an arbitrary portion of the steel material is heated, bent into an arbitrary shape, and strengthened by quenching has been described, but the present disclosure is preferable. The embodiment includes not only the case where the heated high temperature portion of the steel material is bent, but also the case where the heated high temperature portion of the steel material is deformed, such as when twisting or shearing. Therefore, hereinafter, a technique for performing deformation such as bending, twisting, and shearing in the hot state and then performing quenching is referred to as a hot deformation and quenching technique. Among the hot deformation and quenching technologies, the hot bending and quenching (3DQ) technology is used when the only hot deformation is bending, or when the hot deformation includes bending, such as twisting while hot. That's it.
　熱間変形焼入れ用の鋼管の焼入れ性を高めて、熱間変形焼入れ時の加熱温度を低温化するために、熱間変形焼入れ前に少なくとも１回以上、下記各元素の成分量（質量％）に対して下記実験式（１）で示されるＡｃ３変態点以上に加熱して熱間変形焼入れ前の鋼材の組織をマルテンサイト組織またはベイナイト組織に制御することが好ましい。
Ａｃ３＝９１０－２０３×√Ｃ－１５．２×Ｎｉ＋４４．７×Ｓｉ＋１０４×Ｖ＋３１．５×Ｍｏ－３０×Ｍｎ－１１×Ｃｒ －２０×Ｃｕ＋７００×Ｐ＋４００×Ａｌ＋５０×
Ｔｉ ・・・・（１） In order to improve the hardenability of the steel pipe for hot deformation quenching and to lower the heating temperature during hot deformation quenching, the amount of each element below (mass%) at least once before hot deformation quenching On the other hand, it is preferable to control the structure of the steel material before hot deformation quenching to a martensite structure or a bainite structure by heating to an Ac3 transformation point or more shown by the following empirical formula (1).
Ac3 = 910−203 × √C−15.2 × Ni + 44.7 × Si + 104 × V + 31.5 × Mo−30 × Mn−11 × Cr −20 × Cu + 700 × P + 400 × Al + 50 ×
Ti (1)
　このマルテンサイト組織またはベイナイト組織の鋼材を使用した熱間変形焼入れでは、加熱は誘導加熱で行うことが好ましい。加工精度を高めるためには、鋼材の高温で軟化した領域を狭くした方がよく、そのためには、加熱速度は大きい方がよいからである。高温で軟化した領域を狭くするために、鋼材を誘導加熱で局所的に加熱し、局所的に誘導加熱する部分の位置を連続して移動させつつ、冷却装置で冷却する位置も誘導加熱にあわせて移動させる。 In the hot deformation quenching using this martensitic or bainite steel, the heating is preferably performed by induction heating. In order to increase the processing accuracy, it is better to narrow the region softened at a high temperature of the steel material, and for that purpose, a higher heating rate is better. In order to narrow the region softened at high temperature, the steel material is locally heated by induction heating, and the position of the portion to be locally induction heated is continuously moved while the cooling position is also adjusted to the induction heating. To move.
　加熱する温度は、Ａｃ３変態点以上９５０℃以下が好ましい。加熱温度が９５０℃を超えると、加工後の鋼材に表面割れが生じるので好ましくない。表面割れは疲労破壊の起点となるので、表面割れを回避すれば疲労破壊を防止または抑制できる。Ｃｕの融点は１０８５℃である。しかし、鋼材表面に混入するＣｕは純粋なＣｕではないので融点は１０８５℃より低くなり、疲労破壊を回避できる熱間変形焼入れの加熱温度は、表面割れを回避できる９５０℃以下が好ましい。 The heating temperature is preferably from Ac3 transformation point to 950 ° C. When the heating temperature exceeds 950 ° C., surface cracking occurs in the processed steel material, which is not preferable. Since surface cracks are the starting point of fatigue fracture, fatigue fracture can be prevented or suppressed by avoiding surface cracks. The melting point of Cu is 1085 ° C. However, since Cu mixed on the steel material surface is not pure Cu, the melting point is lower than 1085 ° C., and the heating temperature for hot deformation quenching that can avoid fatigue failure is preferably 950 ° C. or less that can avoid surface cracking.
　マルテンサイト組織またはベイナイト組織の鋼材を局所的に誘導加熱した後、局所的に誘導加熱された部分を局所的に連続して変形する。変形は、曲げ、捩りおよびせん断の少なくとも一つであることが好ましい。 After the steel material having a martensite structure or a bainite structure is locally induction-heated, the locally induction-heated portion is locally and continuously deformed. The deformation is preferably at least one of bending, twisting and shearing.
　局所的に誘導加熱された高温部分を局所的に連続して変形した後、マルテンサイト組織またはベイナイト組織の鋼材の局所的に連続して変形された部分を連続して焼入れして、マルテンサイト変態させることによって、焼入れ鋼材を製造する。 After locally locally deforming the high-temperature part that has been induction-heated locally, the locally continuously deformed part of the steel having a martensite or bainite structure is continuously quenched, and martensitic transformation is performed. By hardening, a hardened steel material is manufactured.
　マルテンサイト組織またはベイナイト組織の鋼材の局所的に誘導加熱される部分がＡｃ３変態点に到達してから焼入れ用の冷却が行われるまでの時間は、安定したオーステナイト化を図るためには０．２秒以上、生産性の観点からは１．０秒以下であることが好ましい。 The time from when the locally induction-heated portion of the steel material of the martensite structure or bainite structure reaches the Ac3 transformation point until the quenching cooling is performed is 0.2 in order to achieve stable austenite. It is preferable that it is 1.0 second or less from a viewpoint of productivity more than second.
　上述のように、熱間変形焼入れ前の鋼材の組織をマルテンサイト組織またはベイナイト組織に制御することが好ましい。熱間変形焼入れ前の鋼材の組織をマルテンサイト組織またはベイナイト組織にする熱処理においては、鋼材をＡｃ３＋１０℃以上１１００℃以下に加熱し、その後冷却して、マルテンサイト組織またはベイナイト組織の鋼材にすることが好ましい。７２０℃以上Ａｃ３点以下の加熱温度においても冷却速度を制御して第２相をベイナイトまたはマルテンサイト組織を混在させた組織とすると、熱間変形焼入れ前の熱処理を行わないものに比べ焼入れ性が高まるが，熱間変形焼入れの加熱温度の低温化が十分ではないため、実施の形態では、Ａｃ３＋１０℃以上での加熱を行うことが好ましい。また、熱間変形焼入れの加熱温度が１１００℃を超えると、オーステナイト粒径が粗大化し、マルテンサイト変態時の焼入れ安定性を劣化させ、靱性を低下させるため、熱間変形焼入れの加熱温度は１１００℃以下にすることが好ましい。 As described above, it is preferable to control the structure of the steel material before hot deformation quenching to a martensite structure or a bainite structure. In the heat treatment in which the steel structure before hot deformation quenching is martensitic or bainite, the steel is heated to Ac3 + 10 ° C. or higher and 1100 ° C. or lower, and then cooled to obtain a steel material having a martensitic or bainite structure. Is preferred. When the cooling rate is controlled even at a heating temperature of 720 ° C. or more and Ac3 point or less and the second phase is a structure in which a bainite or martensite structure is mixed, the hardenability is higher than that in which heat treatment before hot deformation quenching is not performed. However, since the temperature of the hot deformation quenching is not sufficiently lowered, it is preferable to perform heating at Ac3 + 10 ° C. or higher in the embodiment. On the other hand, when the heating temperature of the hot deformation quenching exceeds 1100 ° C., the austenite grain size becomes coarse, the quenching stability at the time of martensitic transformation is deteriorated, and the toughness is lowered. It is preferable to set it to below ℃.
　加熱温度と加熱時間は加熱様式によって異なり、急速加熱の場合はより高温まで加熱して完全なオーステナイト化を図ることが好ましい。一方低速加熱の場合は、急速加熱の場合よりも低温での加熱が可能となる。加熱時間は，安定したオーステナイト化を図るためにＡｃ３＋１０℃以上１１００℃以下の温度領域での存在時間が少なくとも０．３秒以上であることが好ましい。上限の規定はないが、過度に長時間の加熱はスケール生成や生産性の低下を招くために好ましくは１０分未満である。 The heating temperature and heating time vary depending on the heating mode, and in the case of rapid heating, it is preferable to heat to a higher temperature to achieve complete austenite. On the other hand, in the case of low-speed heating, heating at a lower temperature is possible than in the case of rapid heating. The heating time is preferably at least 0.3 seconds or more in the temperature range of Ac3 + 10 ° C. to 1100 ° C. in order to achieve stable austenite. An upper limit is not specified, but heating for an excessively long time is preferably less than 10 minutes in order to cause scale generation and productivity reduction.
　加熱後の冷却および温度条件は、狙いとする組織に応じて制御すればよい。ベイナイト組織を得るためには、例えば加熱後、約４５０℃まで冷却してその温度で８０秒以上保持することが好ましい。またマルテンサイト組織を得るためには、加熱後室温まで冷却すればよく、その材料のＣＣＴ（連続冷却変態線図）を見ながら設定すればよい。 The cooling and temperature conditions after heating may be controlled according to the target tissue. In order to obtain a bainite structure, for example, after heating, it is preferable to cool to about 450 ° C. and hold at that temperature for 80 seconds or more. In order to obtain a martensite structure, it may be cooled to room temperature after heating, and may be set while looking at the CCT (continuous cooling transformation diagram) of the material.
　なお、マルテンサイト組織またはベイナイト組織の鋼材は、好ましくは、マルテンサイト組織またはベイナイト組織：８０体積％以上、残部：残留オーステナイト、フェライトおよび炭化物である。この組成であると、オーステナイト化する際に炭化物が溶けやすく、そのためＡｃ３変態点を低下させることが可能となる。その結果熱間変形焼入れ時の加熱温度の低温化が可能となるからである。 The steel material having a martensite structure or a bainite structure is preferably a martensite structure or a bainite structure: 80% by volume or more, and the balance: retained austenite, ferrite, and carbide. With this composition, carbides are easily dissolved when austenitizing, so that the Ac3 transformation point can be lowered. As a result, the heating temperature at the time of hot deformation quenching can be lowered.
　マルテンサイト組織またはベイナイト組織の鋼材を製造する素材としては、好ましくはフェライト－パーライト組織の鋼材が用いられる。 As a material for producing a steel material having a martensite structure or a bainite structure, a steel material having a ferrite-pearlite structure is preferably used.
　熱間変形焼入れ技術は、熱間で曲げ、捩り、せん断等の変形を行いその後焼入れを行う技術であるので、金型等を必要としない。従って、熱間変形焼入れの素材となるマルテンサイト組織またはベイナイト組織の鋼材は、鋼管形状のものを使用することができる。その中でも、溶接鋼管のマルテンサイト組織またはベイナイト組織の鋼材が、熱間変形焼入れ用素材として好適に用いられる。 The hot deformation quenching technique is a technique in which deformation such as bending, twisting, and shearing is performed hot, followed by quenching, so that a mold or the like is not required. Accordingly, a steel material having a steel pipe shape can be used as a steel material having a martensite structure or a bainite structure as a material for hot deformation quenching. Among them, a steel material having a martensitic structure or a bainite structure of a welded steel pipe is preferably used as a material for hot deformation quenching.
　マルテンサイト組織またはベイナイト組織の鋼板を溶接して溶接鋼管を製造するのは、困難である。マルテンサイト組織またはベイナイト組織の鋼材は強度が高く延性が低いため、造管加工性に劣り、溶接の際に割れてしまうからである。そこで、予め溶接鋼管を製造しておき、その溶接鋼管の鋼材を、Ａｃ３変態点＋１０℃以上１１００℃以下に加熱しその後冷却して、マルテンサイト組織あるいはベイナイト組織の鋼材を製造することが好ましい。予め製造しておく溶接鋼管は、フェライト－パーライト組織の鋼板を溶接して製造したフェライト－パーライト組織の溶接鋼管であることが好ましい。フェライト－パーライト組織の鋼材は、強度が高く延性が低いため、造管加工性に優れるからである。そのため、マルテンサイト組織またはベイナイト組織の鋼板を溶接して溶接鋼管を製造するのではなく、フェライト－パーライト組織の鋼板を予め溶接して溶接鋼管を製造しておき、その溶接鋼管を熱処理してマルテンサイト組織またはベイナイト組織の溶接鋼管を製造する方が容易である。熱間圧延後の組織は、一般にフェライト－パーライトであり、割れにくいが、熱間圧延の条件によっては、組織の一部がベイナイトになることもある。ベイナイト組織が３０体積％以下であれば、割れないので、フェライト－パーライト組織の鋼材は、３０体積％以下のベイナイト組織を含んでいてもよい。 It is difficult to manufacture a welded steel pipe by welding a steel sheet having a martensite structure or a bainite structure. This is because a steel material having a martensite structure or a bainite structure has high strength and low ductility, so that it is inferior in pipe forming workability and cracks during welding. Therefore, it is preferable to manufacture a steel material having a martensite structure or a bainite structure by manufacturing a welded steel pipe in advance and heating the steel material of the welded steel pipe to an Ac3 transformation point + 10 ° C. to 1100 ° C. and then cooling. The welded steel pipe manufactured in advance is preferably a welded steel pipe having a ferrite-pearlite structure manufactured by welding steel sheets having a ferrite-pearlite structure. This is because a steel material having a ferrite-pearlite structure has high strength and low ductility, and therefore has excellent tube forming workability. Therefore, a welded steel pipe is not manufactured by welding a steel sheet having a martensite structure or a bainite structure, but a welded steel pipe is manufactured by previously welding a steel sheet having a ferrite-pearlite structure, and the welded steel pipe is heat-treated to obtain a martensite. It is easier to manufacture a welded steel pipe having a site structure or a bainite structure. The structure after hot rolling is generally ferrite-pearlite and is not easily broken, but part of the structure may be bainite depending on the conditions of hot rolling. If the bainite structure is 30% by volume or less, the steel material having a ferrite-pearlite structure may contain a bainite structure of 30% by volume or less because it does not break.
　次に、図１を参照して実施の形態の焼入れ鋼材製造装置を説明する。 Next, a hardened steel material manufacturing apparatus according to an embodiment will be described with reference to FIG.
　実施の形態の焼入れ鋼材製造装置１０は、前熱処理部１１、熱間変形焼入れ部１２、移動装置２１、ガイド４０および変形力付与装置７１を備えている。 The hardened steel material manufacturing apparatus 10 according to the embodiment includes a pre-heat treatment unit 11, a hot deformation quenching unit 12, a moving device 21, a guide 40, and a deformation force applying device 71.
　前熱処理部１１は、加熱装置３２と冷却装置３４とを備えている。加熱装置３２は鋼材移動方向２の上流側に配置され、冷却装置３４は鋼材移動方向２の下流側に配置されている。 The pre-heat treatment unit 11 includes a heating device 32 and a cooling device 34. The heating device 32 is disposed on the upstream side in the steel material moving direction 2, and the cooling device 34 is disposed on the downstream side in the steel material moving direction 2.
　加熱装置３２は、加熱部３１と加熱部３１に電力を供給する電源３５を備えている。加熱装置３２による加熱は、例えば、高周波誘導加熱や抵抗加熱が好適に用いられる。加熱部３１には、高周波誘導加熱の場合には、高周波誘導コイルが好適に用いられ、鋼材１に誘導電流を発生させて鋼材１を加熱する。抵抗加熱の場合には、加熱部３１にはヒータが好適に用いられる。 The heating device 32 includes a heating unit 31 and a power source 35 that supplies power to the heating unit 31. For the heating by the heating device 32, for example, high frequency induction heating or resistance heating is preferably used. In the case of high frequency induction heating, a high frequency induction coil is suitably used for the heating unit 31, and an induction current is generated in the steel material 1 to heat the steel material 1. In the case of resistance heating, a heater is preferably used for the heating unit 31.
　冷却装置３４は、冷却部３３と、冷却部３３に冷却媒体を供給する冷却媒体供給部３７とを備えている。冷却装置３４による冷却は、例えば、水冷や空冷が好適に用いられる。水冷の場合には、冷却媒体としては、例えば、水が好適に用いられる。空冷の場合には、冷却媒体としては、ガスが好適に用いられる。冷却部３３としては、冷却媒体供給部３７から供給される冷却媒体を鋼材１に吹き付けるノズルが好適に用いられる。 The cooling device 34 includes a cooling unit 33 and a cooling medium supply unit 37 that supplies the cooling unit 33 with a cooling medium. For cooling by the cooling device 34, for example, water cooling or air cooling is preferably used. In the case of water cooling, for example, water is suitably used as the cooling medium. In the case of air cooling, gas is preferably used as the cooling medium. As the cooling unit 33, a nozzle that blows the cooling medium supplied from the cooling medium supply unit 37 onto the steel material 1 is preferably used.
　熱間変形焼入れ部１２は、高周波誘導加熱装置５２と水冷装置５４とを備えている。高周波誘導加熱装置５２は鋼材移動方向２の上流側に配置され、冷却装置５４は鋼材移動方向２の下流側に配置されている。 The hot deformation quenching unit 12 includes a high frequency induction heating device 52 and a water cooling device 54. The high frequency induction heating device 52 is arranged on the upstream side in the steel material moving direction 2, and the cooling device 54 is arranged on the downstream side in the steel material moving direction 2.
　高周波誘導加熱装置５２は、誘導加熱コイル５１と誘導加熱コイル５１に高周波電力を供給する高周波電源５５を備えている。高周波電源５５から誘導加熱コイル５１に高周波電力が供給され、誘導加熱コイル５１の内側の鋼材１の一部分６１に局所的に誘導電流を発生させて鋼材１の一部分６１を局所的に誘導加熱する。 The high frequency induction heating device 52 includes an induction heating coil 51 and a high frequency power supply 55 that supplies high frequency power to the induction heating coil 51. High frequency power is supplied from the high frequency power supply 55 to the induction heating coil 51, and an induction current is locally generated in the portion 61 of the steel material 1 inside the induction heating coil 51 to locally induction heat the portion 61 of the steel material 1.
　冷却装置５４は、ノズル５３と、ノズル５３に冷却水を供給する冷却水供給部５７とを備えている。冷却水供給部５７から供給された冷却水をノズル５３によって鋼材１に吹き付け、加熱された鋼材１を急速冷却して鋼材１を焼入れする。 The cooling device 54 includes a nozzle 53 and a cooling water supply unit 57 that supplies cooling water to the nozzle 53. The cooling water supplied from the cooling water supply unit 57 is sprayed onto the steel material 1 by the nozzle 53, and the heated steel material 1 is rapidly cooled to quench the steel material 1.
　変形力付与装置７１は、変形力付与装置７１の保持部７２で鋼材１のノズル５３よりも鋼材移動方向２の下流側の部分を保持する。保持部７２としては、例えば、チャックが好適に用いられる。変形力付与装置７１としては、例えば、マニピュレータが好適に用いられる。マニピュレータとチャックに代えて、可動ローラーダイスも好適に用いられる。変形力付与装置７１によって、誘導加熱コイル５１によって局所的に誘導加熱された一部分６１とノズル５３によって冷却水が吹き付けられ急速冷却される部分６５との間の加熱された高温部分６３に局所的に変形力が加えられる。変形力としては曲げモーネント、捩り力およびせん断力の少なくとも一つが付与されることが好ましい。変形力として、曲げモーネントが付与される場合には、熱間変形焼入れ部１２は、熱間曲げ焼入れ（３ＤＱ）部として機能する。 The deforming force applying device 71 holds the downstream portion of the steel material moving direction 2 from the nozzle 53 of the steel material 1 by the holding portion 72 of the deforming force applying device 71. For example, a chuck is preferably used as the holding unit 72. For example, a manipulator is preferably used as the deforming force applying device 71. Instead of the manipulator and the chuck, a movable roller die is also preferably used. By the deforming force applying device 71, the heated high-temperature portion 63 is locally applied between the portion 61 that is locally induction-heated by the induction heating coil 51 and the portion 65 that is rapidly cooled by being sprayed with cooling water by the nozzle 53. Deformation force is applied. It is preferable that at least one of bending moment, torsional force and shearing force is applied as the deformation force. When a bending moment is applied as the deformation force, the hot deformation and quenching portion 12 functions as a hot bending and quenching (3DQ) portion.
　ガイド４０は、前熱処理部１１の冷却部３３と熱間変形焼入れ部１２の誘導加熱コイル５１との間に設けられている。 The guide 40 is provided between the cooling unit 33 of the pre-heat treatment unit 11 and the induction heating coil 51 of the hot deformation quenching unit 12.
　移動装置２１は、移動装置２１の保持部２３で鋼材１の鋼材移動方向２の上流側の部分を保持して、長尺の鋼材１をその長手方向（鋼材移動方向２）に沿って連続して移動させる。 The moving device 21 holds the upstream portion of the steel material 1 in the steel material moving direction 2 with the holding portion 23 of the moving device 21, and continues the long steel material 1 along its longitudinal direction (steel material moving direction 2). To move.
　加熱部３１、冷却部３３、誘導加熱コイル５１およびノズル５３は、鋼材移動方向２にこの順に配置されている。移動装置２１は、鋼材１を鋼材移動方向２に沿って連続して移動させるので、鋼材１を加熱部３１、冷却部３３、誘導加熱コイル５１およびノズル５３の順に移動させる。また、鋼材１の鋼材移動方向２に沿った連続的な移動によって、誘導加熱コイル５１によって局所的に誘導加熱される鋼材１の一部分６１、変形力付与装置７１によって局所的に変形力が加えられる鋼材１の高温部分６３およびノズル５３によって冷却水が吹き付けられ急速冷却される部分６５も鋼材移動方向２に沿って連続的に移動する。 The heating unit 31, the cooling unit 33, the induction heating coil 51, and the nozzle 53 are arranged in this order in the steel material moving direction 2. Since the moving device 21 continuously moves the steel material 1 along the steel material moving direction 2, the steel material 1 is moved in the order of the heating unit 31, the cooling unit 33, the induction heating coil 51, and the nozzle 53. Further, by the continuous movement of the steel material 1 along the steel material movement direction 2, the deformation force is locally applied by the part 61 of the steel material 1 that is locally induction heated by the induction heating coil 51 and the deformation force applying device 71. The high temperature portion 63 of the steel material 1 and the portion 65 that is rapidly cooled by being sprayed with cooling water by the nozzle 53 also move continuously along the steel material movement direction 2.
　なお、移動装置２１による、鋼材１の加熱部３１、冷却部３３、誘導加熱コイル５１およびノズル５３に対する移動は相対的なものであり、加熱部３１、冷却部３３、誘導加熱コイル５１およびノズル５３を固定して、鋼材１を移動させてもよく、鋼材１を固定して、加熱部３１、冷却部３３、誘導加熱コイル５１およびノズル５３を移動してもよい。 In addition, the movement with respect to the heating part 31, the cooling part 33, the induction heating coil 51, and the nozzle 53 of the steel material 1 by the moving apparatus 21 is relative, and the heating part 31, the cooling part 33, the induction heating coil 51, and the nozzle 53 are relative. May be moved and the steel material 1 may be moved, and the steel material 1 may be fixed and the heating part 31, the cooling part 33, the induction heating coil 51, and the nozzle 53 may be moved.
　移動装置２１としては、例えば、電動サーボシリンダーやマニピュレータが好適に用いられる。保持部２３としては、例えば、チャックが好適に用いられる。 For example, an electric servo cylinder or a manipulator is preferably used as the moving device 21. For example, a chuck is preferably used as the holding unit 23.
　移動装置２１、加熱装置３２、冷却装置３４、高周波誘導加熱装置５２、水冷装置５４、および変形力付与装置７１は制御装置１００に接続され、制御装置１００によって制御される。前述および後述の熱処理や熱間変形焼入れ等は、制御装置１００による、移動装置２１、加熱装置３２、冷却装置３４、高周波誘導加熱装置５２、水冷装置５４、および変形力付与装置７１の制御によって行われる。 The moving device 21, the heating device 32, the cooling device 34, the high frequency induction heating device 52, the water cooling device 54, and the deformation force applying device 71 are connected to the control device 100 and controlled by the control device 100. The heat treatment and hot deformation quenching described above and below are performed by control of the moving device 21, the heating device 32, the cooling device 34, the high frequency induction heating device 52, the water cooling device 54, and the deformation force applying device 71 by the control device 100. Is called.
　前熱処理部１１によって、鋼材１の組織は、マルテンサイトあるいはベイナイトとなる。マルテンサイト組織あるいはベイナイト組織となった鋼材１は、熱間変形焼入れ部１２によって、熱間変形焼入れ処理され、焼入れ鋼材が製造される。前熱処理部１１に供給される鋼材１としては、フェライト－パーライト組織の鋼材が好適に用いられる、鋼材１としては、閉じた断面形状の鋼管が好ましくは用いられ、鋼管としては、溶接鋼管が好ましく用いられる。 The structure of the steel material 1 becomes martensite or bainite by the pre-heat treatment part 11. The steel material 1 having a martensite structure or a bainite structure is subjected to a hot deformation quenching process by the hot deformation quenching part 12 to produce a hardened steel material. As the steel material 1 supplied to the pre-heat treatment section 11, a steel material having a ferrite-pearlite structure is preferably used. As the steel material 1, a steel pipe having a closed cross-sectional shape is preferably used, and as the steel pipe, a welded steel pipe is preferable. Used.
　上記のように、前熱処理部１１と熱間変形焼入れ部１２とを一体化した焼入れ鋼材製造装置１０でインラインでマルテンサイト組織あるいはベイナイト組織の鋼材を製造し、引き続いて熱間変形焼入れ処理された焼入れ鋼材を製造してもいいが、熱間変形焼入れ部１２とは別に前熱処理部１１を備える熱処理装置を設け、予め前熱処理部１１を備える熱処理装置でマルテンサイト組織あるいはベイナイト組織の鋼材を製造しておき、その後、熱間変形焼入れ部１２を備える装置で、熱間変形焼入れ処理された焼入れ鋼材を製造してもよい。また、熱間変形焼入れ部１２を備える装置のみを使用し、最初は、変形力付与装置７１を使用せずに、高周波誘導加熱装置５２と水冷装置５４でマルテンサイト組織あるいはベイナイト組織の鋼材を製造しておき、次に変形力付与装置７１を使用して、高周波誘導加熱装置５２と水冷装置５４と変形力付与装置７１とで熱間変形焼入れ処理された焼入れ鋼材を製造してもよい。 As described above, a steel material having a martensite structure or a bainite structure was produced in-line with a hardened steel material production apparatus 10 in which the pre-heat treatment part 11 and the hot deformation quenching part 12 were integrated, and subsequently hot deformation quenching treatment was performed. A hardened steel material may be manufactured, but a heat treatment device including a pre-heat treatment unit 11 is provided separately from the hot deformation and quenching unit 12, and a steel material having a martensite structure or a bainite structure is manufactured using the heat treatment device including the pre-heat treatment unit 11 in advance. Then, you may manufacture the hardened steel material by which the hot deformation hardening process was carried out with the apparatus provided with the hot deformation hardening part 12 after that. Further, only a device provided with the hot deformation quenching section 12 is used, and initially, a steel material having a martensite structure or a bainite structure is manufactured by the high frequency induction heating device 52 and the water cooling device 54 without using the deformation force applying device 71. In addition, a hardened steel material that has been subjected to hot deformation quenching with the high-frequency induction heating device 52, the water cooling device 54, and the deformable force applying device 71 may be manufactured using the deformable force applying device 71.
　実施の形態のマルテンサイト組織あるいはベイナイト組織の鋼材を製造する素材である鋼材は、好ましくは、
　化学組成が、質量％で、
　Ｃ：０．１２％以上０．６０％以下、
　Ｓｉ：０．００１％以上２．０％以下、
　Ｍｎ：０．５％以上３．０％以下、
　Ｐ：０．０５％以下、
　Ｓ：０．０１％以下、
　ｓｏｌ．Ａｌ：０．００１％以上１．０％以下、
　Ｎ：０．０１％以下、
　Ｂ：０．０１％以下、
　残部：Ｆｅおよび不純物である。 The steel material that is a material for producing the steel material of the martensite structure or bainite structure of the embodiment is preferably,
Chemical composition is mass%,
C: 0.12% to 0.60%,
Si: 0.001% to 2.0%,
Mn: 0.5% to 3.0%,
P: 0.05% or less,
S: 0.01% or less,
sol. Al: 0.001% to 1.0%,
N: 0.01% or less,
B: 0.01% or less,
The balance: Fe and impurities.
　また，前記化学組成が、Ｆｅの一部に代えて、質量％で、
　Ｔｉ：０．００１％以上０．０５％以下、
　Ｎｂ：０．００１％以上０．０５％以下、
　Ｖ　：０．０２％以上０．５％以下、
　Ｃｒ：０．０２％以上０．５％以下、
　Ｍｏ：０．０２以上０．５％以下、
　Ｃｕ：０．０２％以上１．０％以下および
　Ｎｉ：０．０２％以上１．０％以下、
からなる群から選ばれた１種または２種以上の元素を含有してもよい。 Further, the chemical composition is in mass% instead of part of Fe,
Ti: 0.001% or more and 0.05% or less,
Nb: 0.001% or more and 0.05% or less,
V: 0.02% to 0.5%,
Cr: 0.02% to 0.5%,
Mo: 0.02 to 0.5%,
Cu: 0.02% to 1.0% and Ni: 0.02% to 1.0%,
You may contain 1 type, or 2 or more types of elements chosen from the group which consists of.
（１）Ｃは質量％で、０．１２～０．６０％の範囲に制御することが好ましい。
実施の形態における加工方法は、熱処理と加工履歴を制御して、オーステナイト相からマルテンサイト等の硬質相へ組織変態した高強度化・加工品を得る、いわゆる焼入れを利用した製造方法である。鋼板の焼入れ後の強度は、主にマルテンサイト相の硬さを支配するＣ含有量によって決まるため、求める強度に応じてＣ含有量を決定する。実施の形態での狙いの強度１２００ＭＰａ以上を確保するために、Ｃ含有量を０．１２％以上とすることが好ましい。より高強度を安定して得るためには０．２０％超とすることがより好ましい。０．６０％超のＣ含有量の場合、焼入れ後の組織靭性が劣化し、脆性破壊を発生する危険性が高まる。従ってＣ含有量の上限を０．６０％とすることが好ましく、より好ましくは、０．５０％以下である。 (1) C is mass% and is preferably controlled in the range of 0.12 to 0.60%.
The processing method in the embodiment is a manufacturing method using so-called quenching, in which heat treatment and processing history are controlled to obtain a high-strength and processed product that has undergone structural transformation from an austenite phase to a hard phase such as martensite. Since the strength after quenching of the steel sheet is mainly determined by the C content that controls the hardness of the martensite phase, the C content is determined according to the required strength. In order to secure the target strength of 1200 MPa or more in the embodiment, the C content is preferably 0.12% or more. In order to stably obtain higher strength, the content is more preferably over 0.20%. When the C content exceeds 0.60%, the toughness after quenching deteriorates and the risk of causing brittle fracture increases. Therefore, the upper limit of the C content is preferably 0.60%, and more preferably 0.50% or less.
（２）Ｓｉは質量％で、０．００１％～２．０％の範囲に制御することが好ましい。
Ｓｉは、オーステナイト相から低温変態相へ変態するまでの冷却過程において炭化物の生成を抑制するため延性を劣化させることなく、あるいは、延性を向上させて、焼入れ後の強度を高める作用を有する元素である。Ｓｉ含有量が０．００１％未満では上記作用を得ることが困難である。したがって、Ｓｉ含有量は０．００１％以上とすることが好ましい。なお、Ｓｉ含有量を０．０５％以上にすると、延性がさらに向上する。したがって、Ｓｉ含有量は０．０５％以上とすることがより好ましい。一方、Ｓｉ含有量が２．０％超では、上記作用による効果は飽和して経済的に不利となる上、表面性状の劣化が著しくなる。したがって、Ｓｉ含有量は２．０％以下とすることが好ましい。より好ましくは１．５％以下である。 (2) Si is preferably mass%, and is preferably controlled in the range of 0.001% to 2.0%.
Si is an element that has the effect of increasing the strength after quenching without degrading the ductility or improving the ductility in order to suppress the formation of carbides in the cooling process from the austenite phase to the low temperature transformation phase. is there. If the Si content is less than 0.001%, it is difficult to obtain the above effect. Therefore, the Si content is preferably 0.001% or more. Note that when the Si content is 0.05% or more, the ductility is further improved. Therefore, the Si content is more preferably 0.05% or more. On the other hand, if the Si content exceeds 2.0%, the effects of the above action are saturated and disadvantageous economically, and the surface properties are significantly deteriorated. Therefore, the Si content is preferably 2.0% or less. More preferably, it is 1.5% or less.
（３）Ｍｎは質量％で、０．５％～３．０％以下の範囲に制御することが好ましい。
Ｍｎは、鋼の焼入れ性を高め、焼入れ後の強度を安定して確保するために、非常に効果のある元素である。しかし、Ｍｎ含有量が０．５％未満では、実施の形態のような急速冷却条件下でもその効果が十分に得られず、焼入れ後の強度で１２００ＭＰａ以上の引張強度を確保することが非常に困難となる。したがって、Ｍｎ含有量は０．５％以上とすることが好ましい。なお、Ｍｎ含有量を１．０％以上にすると、焼入れ後の強度で１３５０ＭＰａ以上の引張強度を確保することが可能となる。このため、Ｍｎ含有量は１．０％以上とすることがより好ましい。一方、Ｍｎ含有量が３．０％超では、バンド状の組織の不均一組織となり、衝撃特性の劣化が顕著となる。したがって、Ｍｎ含有量は３．０％以下とすることが好ましい。合金コスト等の観点からＭｎ含有量を２．５％以下とすることがより好ましい。 (3) Mn is preferably mass%, and is preferably controlled within the range of 0.5% to 3.0%.
Mn is an extremely effective element for enhancing the hardenability of the steel and ensuring the strength after quenching stably. However, if the Mn content is less than 0.5%, the effect cannot be sufficiently obtained even under the rapid cooling conditions as in the embodiment, and it is very possible to secure a tensile strength of 1200 MPa or more in the strength after quenching. It becomes difficult. Therefore, the Mn content is preferably 0.5% or more. When the Mn content is 1.0% or more, it is possible to ensure a tensile strength of 1350 MPa or more as the strength after quenching. For this reason, it is more preferable that the Mn content is 1.0% or more. On the other hand, if the Mn content exceeds 3.0%, a band-like structure becomes non-uniform, and the impact characteristics are significantly deteriorated. Therefore, the Mn content is preferably 3.0% or less. From the viewpoint of alloy cost and the like, the Mn content is more preferably 2.5% or less.
（４）Ｐは質量％で０．０５％以下に制御することが好ましい。Ｐは、一般には鋼に不可避的に含有される不純物であるが、固溶強化により、強度を高める作用を有するので積極的に含有させてもよい。しかし、Ｐ含有量が０．０５％超では本発明部材と他部材との抵抗溶接性の劣化が著しくなる。また２５００ＭＰａ以上の高強度化を狙った場合に脆性破壊の危険性が高まる。したがって、Ｐ含有量は０．０５％％以下とすることが好ましい。Ｐ含有量はより好ましくは０．０２％以下である。上記作用をより確実に得るには、Ｐ含有量を０．００３％以上とすることが好ましい。 (4) P is preferably controlled to be 0.05% or less by mass%. Generally, P is an impurity inevitably contained in steel, but it may be positively incorporated because it has the effect of increasing strength by solid solution strengthening. However, if the P content exceeds 0.05%, the resistance weldability between the member of the present invention and the other member is significantly deteriorated. In addition, the risk of brittle fracture increases when the strength is increased to 2500 MPa or more. Therefore, the P content is preferably 0.05% or less. The P content is more preferably 0.02% or less. In order to obtain the above action more reliably, the P content is preferably set to 0.003% or more.
（５）Ｓは質量％で０．０１％以下に制御することが好ましい。
Ｓは、鋼に不可避的に含有される不純物であり、ＭｎやＴｉと結合して硫化物を生成して析出する。この析出物量が過度に増加するとその析出物と主相の界面が破壊の起点となることがあるため低いほど好ましい。Ｓ含有量が０．０１％超ではその悪影響が著しくなる。したがって、Ｓ含有量は０．０１％以下とすることが好ましい。より好ましくは０．００３％以下、さらに好ましくは０．００１５％以下である。 (5) It is preferable to control S to 0.01% or less by mass%.
S is an impurity inevitably contained in the steel, and is combined with Mn and Ti to produce sulfide and precipitate. If the amount of this precipitate increases excessively, the interface between the precipitate and the main phase may become the starting point of fracture, so the lower the content, the better. If the S content exceeds 0.01%, the adverse effect becomes significant. Therefore, the S content is preferably 0.01% or less. More preferably, it is 0.003% or less, More preferably, it is 0.0015% or less.
（６）ｓｏｌ．Ａｌは０．００１％～１．０％以下の範囲で制御することが好ましい。
Ａｌは、鋼を脱酸して鋼材を健全化する作用を有する元素であり、また、Ｔｉ等の炭窒化物形成元素の歩留まりを向上させる作用を有する元素でもある。ｓｏｌ．Ａｌ含有量が０．００１％未満では上記作用を得ることが困難となる。したがって、ｓｏｌ．Ａｌ含有量は０．００１％以上とすることが好ましい。より好ましくは０．０１５％以上である。一方、ｓｏｌ．Ａｌ含有量が１．０％超では、溶接性の低下が著しくなるとともに、酸化物系介在物が増加して表面性状の劣化が著しくなる。したがって、ｓｏｌ．Ａｌ含有量は１．０％以下とすることが好ましい。より好ましくは０．０８０％以下である。 (6) sol. Al is preferably controlled in the range of 0.001% to 1.0% or less.
Al is an element having an action of deoxidizing steel to make the steel material sound, and is also an element having an action of improving the yield of carbonitride forming elements such as Ti. sol. If the Al content is less than 0.001%, it is difficult to obtain the above effect. Therefore, sol. The Al content is preferably 0.001% or more. More preferably, it is 0.015% or more. On the other hand, sol. If the Al content exceeds 1.0%, the weldability is significantly lowered and the oxide inclusions are increased, so that the surface properties are remarkably deteriorated. Therefore, sol. The Al content is preferably 1.0% or less. More preferably, it is 0.080% or less.
（７）Ｎは質量％で０．０１％以下に制御することが好ましい。
Ｎは、鋼に不可避的に含有される不純物であり、溶接性の観点からは低いほど好ましい。Ｎ含有量が０．０１％％超では溶接性の低下が著しくなる。したがって、Ｎ含有量は０．０１％以下とすることが好ましい。より好ましくは０．００６％以下である。 (7) It is preferable to control N to 0.01% or less by mass%.
N is an impurity inevitably contained in the steel, and is preferably as low as possible from the viewpoint of weldability. If the N content exceeds 0.01%, the weldability is significantly reduced. Therefore, the N content is preferably 0.01% or less. More preferably, it is 0.006% or less.
（８）Ｂは質量％で０．０１％以下に制御することが好ましい。
Ｂは、低温靭性を高める作用を有する元素である。したがって、Ｂを含有させてもよい。しかし、０．０１％を超えて含有させると、熱間加工性が劣化して、熱間圧延が困難になる。したがって、Ｂ含有量は０．０１％以下とすることが好ましい。なお、上記作用による効果をより確実に得るには、Ｂ含有量を０．０００３％以上とすることが好ましい。 (8) B is preferably controlled to be 0.01% or less by mass.
B is an element having an effect of increasing low temperature toughness. Therefore, B may be contained. However, if the content exceeds 0.01%, the hot workability deteriorates and hot rolling becomes difficult. Therefore, the B content is preferably 0.01% or less. In addition, in order to acquire the effect by the said action more reliably, it is preferable to make B content 0.0003% or more.
（９）その他添加元素
　質量％で、Ｔｉ：０．００１％以上０．０５％以下、Ｎｂ：０．００１％以上０．０５％以下、Ｖ：０．０２％以上０．５％以下、Ｃｒ：０．０２％以上０．５％以下、Ｍｏ：０．０２以上０．５％以下、Ｃｕ：０．０２％以上１．０％以下およびＮｉ：０．０２％以上１．０％以下からなる群から選ばれた１種または２種以上の元素を鋼の焼入れ性を向上させ、かつ焼入れ後の強度を安定して確保するために必要応じて添加してもよい。 (9) Other additive elements In mass%, Ti: 0.001% to 0.05%, Nb: 0.001% to 0.05%, V: 0.02% to 0.5%, Cr : 0.02% to 0.5%, Mo: 0.02 to 0.5%, Cu: 0.02% to 1.0% and Ni: 0.02% to 1.0% One or more elements selected from the group may be added as necessary in order to improve the hardenability of the steel and to ensure a stable strength after quenching.
　本発明者達は、表１に示す化学組成を有する３ＤＱ用の素管を用いて３ＤＱ前の組織制御が３ＤＱ後の表面割れおよび焼入れ性に及ぼす影響を調査した。３ＤＱ用の素管の組織は、鋼板から造管する際の加工性を確保するためにフェライト－パーライトであった。この素管は３ＤＱ前の熱処理を行っていない。３ＤＱ前の組織をマルテンサイトとした素管は、高周波誘導加熱によって３ＤＱ時の加熱温度と同一の１０００℃まで、高周波誘導加熱によって昇温速度８００℃／ｓｅｃで加熱した後、保持時間０ｓｅｃで、室温まで気水にて急冷（降温速度１０００℃／ｓｅｃ）する熱処理により製造した。またベイナイト組織の素管は、同様に高周波誘導加熱によって１０００℃まで昇温速度８００℃／ｓｅｃで加熱した後、Ａｒガスにて４５０℃まで冷却（降温速度５０℃／ｓｅｃ）し、その温度で２４０ｓｅｃ保持した後、Ａｒガスにて室温まで冷却（降温速度５０℃／ｓｅｃ）する熱処理により製造した。３ＤＱ前の熱処理を行わなかったフェライト－パーライト組織の素管、３ＤＱ前の熱処理を行なって製造したマルテンサイト組織の素管および、３ＤＱ前の熱処理を行なって製造したベイナイト組織の素管のＳＥＭ写真を図２、図３、図４にそれぞれ示す。倍率は２０００倍である。 The present inventors investigated the influence of the structure control before 3DQ on the surface crack and hardenability after 3DQ using 3DQ blanks having the chemical composition shown in Table 1. The structure of the 3DQ base tube was ferrite-pearlite to ensure the workability when forming from steel plate. This element tube has not been heat-treated before 3DQ. The raw tube having martensite as the structure before 3DQ is heated to 1000 ° C., which is the same as the heating temperature at the time of 3DQ, by high-frequency induction heating, and heated at a heating rate of 800 ° C./sec by high-frequency induction heating. It was manufactured by a heat treatment that was rapidly cooled to room temperature with air and water (temperature decrease rate: 1000 ° C./sec). Similarly, the bainite-structured tube was heated to 1000 ° C. at a heating rate of 800 ° C./sec by high-frequency induction heating, and then cooled to 450 ° C. with Ar gas (temperature-decreasing rate 50 ° C./sec). After holding for 240 seconds, the substrate was manufactured by heat treatment by cooling to room temperature with Ar gas (temperature decrease rate: 50 ° C./sec). SEM photograph of a ferrite-pearlite structure unprocessed 3DQ tube, a martensitic structure 3DQ preheated, and a bainite structure preheated 3DQ heat treated tube Are shown in FIGS. 2, 3, and 4, respectively. The magnification is 2000 times.
　マルテンサイト組織の素管、ベイナイト組織の素管とフェライト－パーライト組織の素管を用いて、高周波誘導加熱により８００℃～１０５０℃の条件でそれぞれの素管を加熱した後、曲げ半径９５ｍｍの条件で３次元熱間曲げ焼入れ加工（３ＤＱ）を行った。その後、それぞれの加工品の曲げ外側表面を対象に、マイクロスコープを用いて観察して表面割れを分析した。さらに曲げ中央部断面を切り出し、断面の長軸側断面方向に荷重１ｋｇｆでビッカース硬度を測定して焼入れの有無を評価した。 Using a martensite tube, a bainite tube and a ferrite-pearlite tube, each tube was heated at 800 ° C to 1050 ° C by high-frequency induction heating, and the bending radius was 95 mm. 3D hot bending quenching (3DQ) was performed. Thereafter, the outer surface of each processed product was observed with a microscope and analyzed for surface cracks. Furthermore, the bending center section was cut out, and the presence or absence of quenching was evaluated by measuring the Vickers hardness with a load of 1 kgf in the cross section direction of the long axis side of the section.
　図５に、３ＤＱ加熱温度８５０℃の場合の硬度の比較を示す。３ＤＱ前の熱処理がなく３ＤＱ前の組織がフェライト－パーライトの場合には、８５０℃で狙いの硬度（ビッカース硬度４７０）が得られていないことがわかる。３ＤＱ前の素管の組織をベイナイトまたはマルテンサイトとした場合は、８５０℃でも狙いの硬度（ビッカース硬度４７０）が得られることがわかる。また３ＤＱ前の素管の組織がマルテンサイトよりはベイナイトの方がより高い硬度が得られることがわかる。 FIG. 5 shows a comparison of hardness when the 3DQ heating temperature is 850 ° C. When there is no heat treatment before 3DQ and the structure before 3DQ is ferrite-pearlite, it can be seen that the target hardness (Vickers hardness 470) is not obtained at 850 ° C. It can be seen that when the structure of the raw tube before 3DQ is bainite or martensite, the target hardness (Vickers hardness 470) can be obtained even at 850 ° C. Further, it can be seen that bainite has a higher hardness than martensite in the structure of the raw tube before 3DQ.
　図６Ａ、図６Ｂに、３ＤＱ加熱温度９００℃の場合の３ＤＱ前の熱処理有無によるマイクロスコープによる表面割れ観察写真の比較を示す。倍率は１７５倍である。図６Ａは、３ＤＱ前の熱処理がなく３ＤＱ前の組織がフェライト－パーライトの素管を使用した場合であり、図６Ｂは、３ＤＱ前の熱処理を行い、３ＤＱ前の組織をマルテンサイトとした素管を用いた場合である。３ＤＱ前の熱処理がなく３ＤＱ前の組織がフェライト－パーライトの素管を使用した場合には、表面割れが発生したが、３ＤＱ前の熱処理を行い、３ＤＱ前の組織をマルテンサイトとした素管を用いた場合は、９００℃の３ＤＱ加熱温度でも表面割れが発生しないことがわかる。 FIG. 6A and FIG. 6B show a comparison of microscopic surface crack observation photographs with and without heat treatment before 3DQ when the 3DQ heating temperature is 900 ° C. FIG. The magnification is 175 times. 6A shows the case where there is no heat treatment before 3DQ and the structure before 3DQ uses a ferrite-pearlite tube, and FIG. 6B shows the tube where the heat treatment before 3DQ is performed and the structure before 3DQ is martensite. Is used. When there was no heat treatment before 3DQ and the structure before 3DQ used a ferrite-pearlite tube, surface cracking occurred, but heat treatment before 3DQ was performed, and the tube with the structure before 3DQ was martensite. When used, it can be seen that surface cracking does not occur even at a 3DQ heating temperature of 900 ° C.
　表２に評価結果をまとめて示す。割れの有無はマイクロスコープ（倍率１７５倍）により確認した。ビッカース硬度４７０以上の場合に焼入れ有と判定した。 Table 2 summarizes the evaluation results. The presence or absence of cracks was confirmed with a microscope (magnification of 175 times). When the Vickers hardness was 470 or more, it was determined that there was quenching.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　３ＤＱ前の熱処理を行い、３ＤＱ前の組織をベイナイトまたはマルテンサイトとした素管を用いた場合は、８００℃～９５０℃の条件で表面割れがなく、また８５０℃以上の条件で狙いの焼入れ性が確保できることがわかる。これに対して、３ＤＱ前の熱処理がなく３ＤＱ前の組織がフェライト－パーライトの鋼材を３ＤＱの素管として用いた場合には、８００～８５０℃の３ＤＱ加熱温度では表面割れがないが、９００℃～１０５０℃で表面割れが存在した。９５０℃以上で狙いの焼入れ性が確保できていたが、８００℃～９００℃では、狙いの焼入れ性が確保できていなかった。すなわち、３ＤＱ前の熱処理による３ＤＱ前の組織制御を行なわない素管を用いた場合には、表面割れなく狙いの硬さを得ることは不可能であるのに対し、３ＤＱ前の熱処理を行い、３ＤＱ前の組織をベイナイトまたはマルテンサイトとした素管を用いて３ＤＱを行う場合は、８５０℃～９５０℃の条件で表面割れもなく、安定した狙い硬さの加工品が得られた。表面割れは、疲労破壊の起点であるので、表面割れを回避すれば疲労破壊を防止または抑制できる。 When heat treatment before 3DQ is performed and a tube with the structure before 3DQ is bainite or martensite is used, there is no surface cracking at 800 ° C to 950 ° C, and the target hardenability at 850 ° C or higher. Can be secured. On the other hand, when there is no heat treatment before 3DQ and the structure before 3DQ is a ferrite-pearlite steel material used as a 3DQ blank, there is no surface cracking at a 3DQ heating temperature of 800 to 850 ° C., but 900 ° C. There were surface cracks at ˜1050 ° C. The target hardenability was secured at 950 ° C. or higher, but the target hardenability was not ensured at 800 ° C. to 900 ° C. That is, when using a tube that does not perform the structure control before 3DQ by the heat treatment before 3DQ, it is impossible to obtain the target hardness without surface cracking, whereas the heat treatment before 3DQ is performed, When 3DQ was performed using a raw tube whose structure before 3DQ was bainite or martensite, a processed product having a stable target hardness was obtained without surface cracking at 850 ° C to 950 ° C. Since surface cracks are the starting point of fatigue fracture, fatigue fracture can be prevented or suppressed by avoiding surface cracks.
　以上まとめると、３ＤＱ前にベイナイトまたはマルテンサイト組織とする熱処理を施した素管を用いることにより、制御された素管の組織によって３ＤＱ工程の加熱時に短時間でオーステナイト化変態が可能となって安定した焼入れ性が実現できる。すなわち、厳しい曲げ加工条件においても表面割れがなく、安定した焼入れ性を確保することができる。 In summary, by using an element tube that has been heat-treated to have a bainite or martensite structure before 3DQ, the structure of the controlled element tube enables austenite transformation in a short time when heated in the 3DQ process, and is stable. Hardenability can be realized. That is, there is no surface cracking even under severe bending conditions, and stable hardenability can be ensured.
　２０１５年１０月５日に出願された日本国特許出願２０１５－１９７９５８号の開示は、その全体が参照により本開示に取り込まれる。
　本開示に記載された全ての文献、特許出願、および技術規格は、個々の文献、特許出願、および技術規格が参照により取り込まれることが具体的かつ個々に記された場合と同程度に、本開示に参照により取り込まれる。 The disclosure of Japanese Patent Application No. 2015-197958 filed on October 5, 2015 is incorporated herein by reference in its entirety.
All documents, patent applications, and technical standards mentioned in this disclosure are as if they were specifically and individually stated that each individual document, patent application, and technical standard was incorporated by reference. The disclosure is incorporated by reference.
　以上、種々の典型的な実施の形態および実施例を説明してきたが、本発明はそれらの実施の形態および実施例に限定されない。本発明の範囲は、次の請求の範囲によってのみ限定されるものである。 Although various typical embodiments and examples have been described above, the present invention is not limited to these embodiments and examples. The scope of the present invention is limited only by the following claims.

Claims (29)

  1. 　マルテンサイト組織またはベイナイト組織の鋼材を、局所的に誘導加熱する部分の位置を連続して移動させつつ、Ａｃ３変態点以上９５０℃以下の温度に局所的に誘導加熱する工程と、
    　前記マルテンサイト組織またはベイナイト組織の鋼材の局所的に誘導加熱された部分を局所的に連続して変形する工程と、
    　前記マルテンサイト組織またはベイナイト組織の鋼材の局所的に連続して変形された部分を連続して焼入れする工程と、を備える焼入れ鋼材の製造方法。     A step of locally inductively heating a steel material having a martensite structure or a bainite structure to a temperature not lower than the Ac3 transformation point and not higher than 950 ° C. while continuously moving the position of the portion to be locally induction heated;
    A step of locally continuously deforming a locally induction-heated portion of the steel material of the martensite structure or bainite structure;
    And a step of continuously quenching a locally continuously deformed portion of the steel material having the martensite structure or the bainite structure.
  2. 　鋼材を、Ａｃ３変態点＋１０℃以上１１００℃以下に加熱しその後冷却して、前記マルテンサイト組織あるいはベイナイト組織の鋼材を製造する工程をさらに備える請求項１に記載の焼入れ鋼材の製造方法。 The method for producing a quenched steel material according to claim 1, further comprising a step of heating the steel material to an Ac3 transformation point + 10 ° C to 1100 ° C and then cooling to produce the steel material having the martensite structure or the bainite structure.
  3. 　溶接鋼管の鋼材を、Ａｃ３変態点＋１０℃以上１１００℃以下に加熱しその後冷却して、前記マルテンサイト組織あるいはベイナイト組織の鋼材を製造する工程をさらに備える請求項１に記載の焼入れ鋼材の製造方法。 The method for producing a hardened steel material according to claim 1, further comprising a step of heating the steel material of the welded steel pipe to an Ac3 transformation point + 10 ° C to 1100 ° C and then cooling to produce the steel material having the martensite structure or the bainite structure. .
  4. 　前記鋼材は、フェライト－パーライト組織の鋼材である請求項２または請求項３に記載の焼入れ鋼材の製造方法。 4. The method of manufacturing a hardened steel material according to claim 2, wherein the steel material is a steel material having a ferrite-pearlite structure.
  5. 　前記マルテンサイト組織またはベイナイト組織の鋼材は溶接鋼管である請求項１から請求項４のいずれか一項に記載の焼入れ鋼材の製造方法。 The method for producing a hardened steel material according to any one of claims 1 to 4, wherein the steel material having the martensite structure or the bainite structure is a welded steel pipe.
  6. 　前記マルテンサイト組織またはベイナイト組織の鋼材は、
    　マルテンサイト組織またはベイナイト組織：８０体積％以上、
    　残部：残留オーステナイト、フェライトおよび炭化物である、請求項１から請求項５のいずれか一項に記載の焼入れ鋼材の製造方法。     The steel material of the martensite structure or bainite structure,
    Martensite structure or bainite structure: 80% by volume or more,
    Remainder: The manufacturing method of the hardened steel materials as described in any one of Claims 1-5 which is a retained austenite, a ferrite, and a carbide | carbonized_material.
  7. 　前記マルテンサイト組織またはベイナイト組織を製造する前の鋼材は、
    　化学組成が、質量％で、
    　Ｃ：０．１２％以上０．６０％以下、
    　Ｓｉ：０．００１％以上２．０％以下、
    　Ｍｎ：０．５％以上３．０％以下、
    　Ｐ：０．０５％以下、
    　Ｓ：０．０１％以下、
    　ｓｏｌ．Ａｌ：０．００１％以上１．０％以下、
    　Ｎ：０．０１％以下、
    　Ｂ：０．０１％以下、
    　残部：鉄および不純物
    である請求項２から請求項４のいずれか一項に記載の焼入れ鋼材の製造方法。     Steel material before producing the martensite structure or bainite structure,
    Chemical composition is mass%,
    C: 0.12% to 0.60%,
    Si: 0.001% to 2.0%,
    Mn: 0.5% to 3.0%,
    P: 0.05% or less,
    S: 0.01% or less,
    sol. Al: 0.001% to 1.0%,
    N: 0.01% or less,
    B: 0.01% or less,
    The balance: iron and impurities. The method for producing a hardened steel material according to any one of claims 2 to 4.
  8. 　前記化学組成が、質量％で、
    　Ｔｉ：０．００１％以上０．０５％以下、
    　Ｎｂ：０．００１％以上０．０５％以下、
    　Ｖ　：０．０２％以上０．５％以下、
    　Ｃｒ：０．０２％以上０．５％以下、
    　Ｍｏ：０．０２以上０．５％以下、
    　Ｃｕ：０．０２％以上１．０％以下および
    　Ｎｉ：０．０２％以上１．０％以下、からなる群から選択された１種または２種以上の元素を含有する請求項７に記載の焼入れ鋼材の製造方法。     The chemical composition is mass%,
    Ti: 0.001% or more and 0.05% or less,
    Nb: 0.001% or more and 0.05% or less,
    V: 0.02% to 0.5%,
    Cr: 0.02% to 0.5%,
    Mo: 0.02 to 0.5%,
    The element according to claim 7, comprising one or more elements selected from the group consisting of Cu: 0.02% to 1.0% and Ni: 0.02% to 1.0%. A method of manufacturing hardened steel.
  9. 　前記フェライト－パーライト組織の鋼材は、３０体積％以下のベイナイト組織を含む請求項４に記載の焼入れ鋼材の製造方法。 The method for producing a hardened steel material according to claim 4, wherein the steel material having a ferrite-pearlite structure contains a bainite structure of 30% by volume or less.
  10. 　前記鋼材を、Ａｃ３変態点＋１０℃以上１１００℃以下に、０．３秒以上、１０分未満加熱する請求項２から請求項４のいずれか一項に記載の焼入れ鋼材の製造方法。 The method for producing a hardened steel material according to any one of claims 2 to 4, wherein the steel material is heated to an Ac3 transformation point + 10 ° C or higher and 1100 ° C or lower for 0.3 second or longer and less than 10 minutes.
  11. 　前記マルテンサイト組織またはベイナイト組織の鋼材の局所的に誘導加熱される部分がＡｃ３変態点に到達してから焼入れ用の冷却が行われるまでの時間が０．２秒以上１．０秒以下である請求項１から請求項１０のいずれか一項に記載の焼入れ鋼材の製造方法。 The time from when the locally induction-heated portion of the steel material of the martensite structure or bainite structure reaches the Ac3 transformation point until cooling for quenching is 0.2 second or more and 1.0 second or less. The manufacturing method of the hardened steel materials as described in any one of Claims 1-10.
  12. 　前記変形は、曲げ、捩り、せん断の少なくとも一つである請求項１から請求項１１のいずれか一項に記載の焼入れ鋼材の製造方法。 The method for producing a hardened steel material according to any one of claims 1 to 11, wherein the deformation is at least one of bending, twisting, and shearing.
  13. 　鋼材を加熱する第１の加熱装置と、
    　加熱された前記鋼材を冷却する第１の冷却装置と、
    　前記鋼材を局所的に誘導加熱する第２の加熱装置と、
    　前記鋼材の局所的に誘導加熱された部分に局所的に変形力を付与する変形力付与装置と、
    　前記鋼材の局所的に変形力を付与された部分を冷却して焼入れする第２の冷却装置と、
    　前記鋼材を連続して移動させる移動装置と、を備え、
    　前記移動装置は、前記鋼材を、前記第１の加熱装置、前記第１の冷却装置、前記第２の加熱装置および前記第２の冷却装置に対して相対的に移動させる移動装置であり、
    　前記第１の加熱装置、前記第１の冷却装置、前記第２の加熱装置および前記第２の冷却装置は前記鋼材の相対的な移動方向にこの順に配置されている、焼入れ鋼材の製造装置。     A first heating device for heating the steel material;
    A first cooling device that cools the heated steel material;
    A second heating device for locally inductively heating the steel material;
    A deforming force applying device for applying a deforming force locally to the locally heated portion of the steel material;
    A second cooling device for cooling and quenching a locally deformed portion of the steel material;
    A moving device for continuously moving the steel material,
    The moving device is a moving device that moves the steel material relative to the first heating device, the first cooling device, the second heating device, and the second cooling device;
    The said 1st heating apparatus, the said 1st cooling apparatus, the said 2nd heating apparatus, and the said 2nd cooling apparatus are the manufacturing apparatus of hardened steel materials arrange | positioned in this order in the relative moving direction of the said steel materials.
  14. 　前記移動装置、前記第１の加熱装置、前記第１の冷却装置、前記第２の加熱装置、前記第２の冷却装置および前記変形力付与装置を制御する制御装置、をさらに備え、
    　前記制御装置は、前記移動装置により前記鋼材を、前記第１の加熱装置、前記第１の冷却装置、前記第２の加熱装置および前記第２の冷却装置に対してこの順で連続的に相対的に移動させながら、前記第１の加熱装置により前記鋼材をＡｃ３変態点＋１０℃以上１１００℃以下に加熱し、前記加熱した鋼材を前記第１の冷却装置により冷却し、前記第２の加熱装置により前記鋼材をＡｃ３変態点以上９５０℃以下に局所的に連続して誘導加熱し、前記鋼材の局所的に誘導加熱された部分に前記変形力付与装置により変形力を局所的に連続的に付与して前記鋼材を連続して変形し、前記第２の冷却装置により前記鋼材の局所的に変形された部分を連続して冷却して焼入れするように、前記移動装置、前記第１の加熱装置、前記第１の冷却装置、前記第２の加熱装置、前記第２の冷却装置および前記変形力付与装置を制御する請求項１３に記載の焼入れ鋼材の製造装置。     A control device for controlling the moving device, the first heating device, the first cooling device, the second heating device, the second cooling device, and the deformation force applying device;
    The control device causes the moving device to continuously move the steel material relative to the first heating device, the first cooling device, the second heating device, and the second cooling device in this order. The steel material is heated to Ac3 transformation point + 10 ° C. or higher and 1100 ° C. or lower by the first heating device while being moved, and the heated steel material is cooled by the first cooling device, and the second heating device. The steel material is induction-heated locally continuously from the Ac3 transformation point to 950 ° C., and the deformation force is applied to the locally heated portion of the steel material by the deformation-force applying device. Then, the moving device and the first heating device are configured so that the steel material is continuously deformed, and the locally deformed portion of the steel material is continuously cooled and quenched by the second cooling device. The first cooling device, Serial second heating apparatus, manufacturing apparatus hardened steel according to claim 13 for controlling the second cooling device and the deforming force applying device.
  15. 　前記制御装置は、前記鋼材を、Ａｃ３変態点＋１０℃以上１１００℃以下に、０．３秒以上、１０分未満加熱するように、前記移動装置、前記第１の加熱装置および前記第１の冷却装置を制御する請求項１４に記載の焼入れ鋼材の製造装置。 The said control apparatus is the said moving apparatus, the said 1st heating apparatus, and the said 1st cooling so that the said steel materials may be heated to Ac3 transformation point +10 degreeC or more and 1100 degrees C or less for 0.3 second or more and less than 10 minutes. The apparatus for manufacturing a hardened steel material according to claim 14, wherein the apparatus is controlled.
  16. 　前記鋼材の局所的に誘導加熱される部分がＡｃ３変態点に到達してから焼入れ用の冷却が行われるまでの時間が０．２秒以上１．０秒以下であるように前記移動装置、前記第２の加熱装置および前記第２の冷却装置を制御する請求項１４または請求項１５に記載の焼入れ鋼材の製造装置。 The moving device, wherein the time from when the locally heated portion of the steel material reaches the Ac3 transformation point to when quenching cooling is performed is 0.2 second or more and 1.0 second or less, The manufacturing apparatus of the hardened steel material of Claim 14 or Claim 15 which controls a 2nd heating apparatus and a said 2nd cooling device.
  17. 前記変形は、曲げ、捩り、せん断の少なくとも一つである請求項１３から請求項１６のいずれか一項に記載の焼入れ鋼材の製造装置。 The said deformation | transformation is at least one of a bending, a twist, and a shear, The manufacturing apparatus of the hardened steel materials as described in any one of Claims 13-16.
  18. 　誘導加熱後焼入れして焼入れ鋼材を製造するためのマルテンサイト組織あるいはベイナイト組織の焼入れ用鋼材。 鋼 Steel for quenching with a martensite or bainite structure to produce a hardened steel by induction heating and quenching.
  19. 　前記マルテンサイト組織あるいはベイナイト組織の焼入れ用鋼材は、溶接鋼管である請求項１８記載の焼入れ用鋼材。 The steel for quenching according to claim 18, wherein the steel for quenching having the martensite structure or the bainite structure is a welded steel pipe.
  20. 　マルテンサイト組織あるいはベイナイト組織の溶接鋼管である焼入れ用鋼材。 Quenching steel that is a welded steel pipe with martensite or bainite structure.
  21. 　鋼材を、Ａｃ３変態点＋１０℃以上１１００℃以下に加熱しその後冷却して製造した焼入れ用鋼材。 Quenching steel manufactured by heating the steel to Ac3 transformation point + 10 ° C to 1100 ° C and then cooling.
  22. 　溶接鋼管の鋼材を、Ａｃ３変態点＋１０℃以上１１００℃以下に加熱しその後冷却して製造した焼入れ用鋼材。 Quenching steel produced by heating a steel material of a welded steel pipe to Ac3 transformation point + 10 ° C. to 1100 ° C. and then cooling.
  23. 　前記鋼材は、フェライト－パーライト組織の鋼材である請求項２１または請求項２２に記載の焼入れ用鋼材。 The steel material for quenching according to claim 21 or 22, wherein the steel material is a steel material having a ferrite-pearlite structure.
  24. 　前記マルテンサイト組織またはベイナイト組織の鋼材は、
    　マルテンサイト組織またはベイナイト組織：８０体積％以上、
    　残部：残留オーステナイト、フェライトおよび炭化物である、請求項１８から請求項２０のいずれか一項に記載の焼入れ用鋼材。     The steel material of the martensite structure or bainite structure,
    Martensite structure or bainite structure: 80% by volume or more,
    The balance: The steel for hardening according to any one of claims 18 to 20, which is retained austenite, ferrite and carbide.
  25. 　前記鋼材は、
    　化学組成が、質量％で、
    　Ｃ：０．１２％以上０．６０％以下、
    　Ｓｉ：０．００１％以上２．０％以下、
    　Ｍｎ：０．５％以上３．０％以下、
    　Ｐ：０．０５％以下、
    　Ｓ：０．０１％以下、
    　ｓｏｌ．Ａｌ：０．００１％以上１．０％以下、
    　Ｎ：０．０１％以下、
    　Ｂ：０．０１％以下、
    　残部：鉄および不純物
    である請求項２１から請求項２３のいずれか一項に記載の焼入れ用鋼材。     The steel material is
    Chemical composition is mass%,
    C: 0.12% to 0.60%,
    Si: 0.001% to 2.0%,
    Mn: 0.5% to 3.0%,
    P: 0.05% or less,
    S: 0.01% or less,
    sol. Al: 0.001% to 1.0%,
    N: 0.01% or less,
    B: 0.01% or less,
    24. The balance: steel for quenching according to any one of claims 21 to 23, which is iron and impurities.
  26. 　前記化学組成が、質量％で、
    　Ｔｉ：０．００１％以上０．０５％以下、
    　Ｎｂ：０．００１％以上０．０５％以下、
    　Ｖ　：０．０２％以上０．５％以下、
    　Ｃｒ：０．０２％以上０．５％以下、
    　Ｍｏ：０．０２以上０．５％以下、
    　Ｃｕ：０．０２％以上１．０％以下および
    　Ｎｉ：０．０２％以上１．０％以下、
    からなる群から選択された１種または２種以上の元素を含有する請求項２５に記載の焼入れ用鋼材。     The chemical composition is mass%,
    Ti: 0.001% or more and 0.05% or less,
    Nb: 0.001% or more and 0.05% or less,
    V: 0.02% to 0.5%,
    Cr: 0.02% to 0.5%,
    Mo: 0.02 to 0.5%,
    Cu: 0.02% to 1.0% and Ni: 0.02% to 1.0%,
    The steel for quenching according to claim 25, containing one or more elements selected from the group consisting of:
  27. 　前記フェライト－パーライト組織の鋼材は、３０体積％以下のベイナイト組織を含む請求項２３に記載の焼入れ用鋼材。 The steel material for quenching according to claim 23, wherein the steel material having a ferrite-pearlite structure includes a bainite structure of 30% by volume or less.
  28. 　前記鋼材を、Ａｃ３変態点＋１０℃以上１１００℃以下に、０．３秒以上、１０分未満加熱する請求項２１から請求項２３のいずれか一項に記載の焼入れ用鋼材。 The steel material for quenching according to any one of claims 21 to 23, wherein the steel material is heated to an Ac3 transformation point + 10 ° C or higher and 1100 ° C or lower for 0.3 second or more and less than 10 minutes.
  29. 　請求項１８から請求項２８のいずれか一項記載の焼入れ用鋼材を、局所的に誘導加熱する部分の位置を連続して移動させつつ、Ａｃ３変態点以上９５０℃以下の温度に局所的に誘導加熱し、前記鋼材の局所的に誘導加熱された部分を局所的に連続して変形し、前記鋼材の局所的に連続して変形された部分を連続して焼入れして製造した焼入れ鋼材。 The steel material for quenching according to any one of claims 18 to 28 is locally induced to a temperature not lower than the Ac3 transformation point and not higher than 950 ° C while continuously moving the position of the portion to be locally induction heated. A quenched steel material produced by heating, locally and continuously deforming a locally induction-heated portion of the steel material, and continuously quenching the locally continuously deformed portion of the steel material.
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