WO2021187473A1 - Steel for solid-state welding, steel material for solid-state welding, solid-state welded joint, and solid-state welded structure - Google Patents

Steel for solid-state welding, steel material for solid-state welding, solid-state welded joint, and solid-state welded structure Download PDF

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WO2021187473A1
WO2021187473A1 PCT/JP2021/010577 JP2021010577W WO2021187473A1 WO 2021187473 A1 WO2021187473 A1 WO 2021187473A1 JP 2021010577 W JP2021010577 W JP 2021010577W WO 2021187473 A1 WO2021187473 A1 WO 2021187473A1
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solid
steel
joint
solid phase
phase bonding
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Japanese (ja)
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藤井　英俊
浩作 潮田
知也 柳楽
好昭 森貞
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国立大学法人大阪大学
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
    • B23K20/12—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating the heat being generated by friction; Friction welding
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C37/00—Cast-iron alloys
    • C22C37/10—Cast-iron alloys containing aluminium or silicon
    • 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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium

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  • the present invention Steel composition by mass% C: 0.20 to 2.14%, Total of Si and Al: 1.00 to 3.00%, Mn: 2.00 to 5.00%, and It contains at least one of V: more than 0.1% and 3.0% or less, W: more than 1.0% and 6.0% or less, and Mo: more than 1.0% and 6.0% or less.
  • the balance is composed of Fe and unavoidable impurities only.
  • a steel for solid phase bonding which is characterized by the above.
  • the carbon content is preferably 0.20 to 0.45% by mass, more preferably 0.20 to 0.30% by mass, and most preferably 0.20 to 0.25% by mass. ..
  • the tensile strength of the base metal and the solid-phase bonding portion is 1000 MPa or more at 0.20% by mass, which is the lower limit of the carbon content, so that good ductility can be ensured.
  • the upper limit is preferably a small value as long as the desired tensile strength can be obtained.
  • the upper limit of the Mn content is set to 5.00% by mass.
  • the Mn content is preferably 3.00 to 5.00% by mass, and when ductility is important, it is 2.00% by mass or more and less than 3.00% by mass. preferable.
  • each alloying element to form carbides is Ti> Ta> Nb> V> W> Mo> Cr> Mn> (Fe)> Ni, Co, Al, Si. Since Ti, Ta and Nb have a too strong tendency to form carbides, for example, carbides are easily generated even in austenite, and the amount of secondary carbides generated in the heat-affected zone decreases, so that the heat-affected zone can be effectively divided. Cannot be next cured. On the other hand, Cr and Mn have a too weak tendency to form carbides, and the hardness of the carbides is also relatively low, so that the heat-affected zone cannot be effectively secondary-cured.
  • Mo in an amount of more than 1.0% and 6.0% or less, and more preferably Mo is added in an amount of more than 2.0% and 4.0% or less. ..
  • Mo By adding Mo, it is possible to develop a remarkable secondary curing in the heat-affected zone as compared with the case of adding V or W.
  • the Vickers hardness of the solid phase bonding steel material is 400 HV or more
  • the Vickers hardness of the solid phase joint is 400 HV or more
  • the Vickers hardness of the heat affected zone in the vicinity of the solid phase joint is 400 HV or more. It is preferably 400 HV or more.
  • a more preferable Vickers hardness is 450 HV or more for the steel material for solid phase bonding, the solid phase bonding portion, and the heat-affected zone.
  • the tensile strength is about 1200 MPa
  • the Vickers hardness of the steel material is 450 HV
  • the tensile strength is about 1350 MPa.
  • the solid phase joint of the present invention preferably has a tensile strength of 1000 MPa or more and an elongation of 20% or more at room temperature, more preferably 1200 MPa or more and an elongation of 20% or more, 1500 MPa or more. Most preferably, the elongation is 20% or more.
  • These values can be achieved by imparting high tensile properties to the base metal and the solid phase joint and suppressing softening in the heat-affected zone. Since the solid-phase joint has these tensile properties, it can be sufficiently used as a joint having mechanical properties equal to or higher than those of ultra-high-strength steel in applications requiring high strength and reliability.
  • the present invention also provides a solid phase bonding structure characterized by having the solid phase bonding joint of the present invention.
  • the material, shape, and size of the structural part other than the solid-phase joint are not particularly limited, and various conventionally known structures can be used.
  • the steel for solid-phase welding of the present invention uses solid-state bonding.
  • the problem is overcome by assuming that. Further, by adding an appropriate amount of Si, Al and Mn, good ductility is imparted to the base material and the joint portion. Further, by adding at least one of V, W and Mo, secondary carbides containing these are generated, and the decrease in hardness of the heat-affected zone is suppressed.
  • each component will be described in detail.
  • Mn 2.00 to 5.00 mass%
  • TRIP martensite transformation-induced plasticity
  • a fine martensite structure can be formed in the solid phase bonding portion by adding 2.00% by mass or more of Mn.
  • the upper limit of the Mn content is set to 5.00% by mass.
  • the Mn content is preferably 3.00 to 5.00% by mass, and when ductility is important, it is 2.00% by mass or more and less than 3.00% by mass. preferable.
  • B 0.0040% by mass or less B has the effect of segregating at the austenite grain boundary during rolling to improve the hardenability, but if it exceeds 0.0040% by mass, the toughness of the HAZ portion deteriorates, so it is 0. It is preferably 0040% by mass or less.
  • a secondary carbide containing at least one of V, W and Mo in the heat-affected zone.
  • a secondary carbide containing at least one of V, W and Mo in the heat-affected zone.
  • the solid-phase bonded structure is not particularly limited as long as the effect of the present invention is not impaired, and examples thereof include structural parts of transportation equipment such as automobiles, ships and railroad vehicles, various building structures, bridges and iron pipes. Can be done.
  • Example 3 A steel sheet (Steel 3 for solid phase bonding) was obtained in the same manner as in Example 1 except that the composition of Example 3 shown in Table 1 was used. Further, friction stir welding was performed in the same manner as in Example 1.
  • Comparative Example 3 A steel sheet (Steel 3 for comparative solid phase bonding) was obtained in the same manner as in Example 1 except that the composition of Comparative Example 3 shown in Table 1 was used. Further, friction stir welding was performed in the same manner as in Example 1.

Abstract

The present invention provides steel for solid-state welding and a steel material for solid-state welding that are steel for which the tensile properties of the parent material and a joint obtained by solid-state welding are equivalent or superior to those of high tensile strength steel, and to which minimal amounts of only relatively inexpensive alloy elements have been added, wherein softening of a heat-affected part is suppressed by the addition of the minimal amounts of the alloy elements. The present invention also provides: a solid-state welded joint that is formed from steel for solid-state welding to which minimal amounts of only relatively inexpensive alloy elements have been added, wherein the tensile properties of the parent material and the joint are equivalent or superior to those of high tensile strength steel; and a solid-state welded structure including said joint. Steel for solid-state welding according to the present invention is characterized in that, in terms of mass%, the steel composition thereof contains C: 0.20-2.14%, Si and Al combined: 1.00-3.00%, Mn: 2.00-5.00%, and at least one substance from among V: more than 0.1% but not more than 3.0%, W: more than 1.0% but not more than 6.0%, and Mo: more than 1.0% but not more than 6.0%, with the remainder being only Fe and unavoidable impurities.

Description

固相接合用鋼、固相接合用鋼材、固相接合継手及び固相接合構造物Solid-phase bonding steel, solid-phase bonding steel, solid-phase bonding joints and solid-phase bonding structures
　本発明は固相接合を好適に用いることができる固相接合用鋼及び固相接合用鋼材、当該固相接合用鋼からなる固相接合継手及び固相接合構造物に関する。 The present invention relates to a solid-phase bonding steel and a solid-phase bonding steel material to which solid-phase bonding can be preferably used, and a solid-phase bonding joint and a solid-phase bonding structure made of the solid-phase bonding steel.
　従来の溶融溶接よりも接合部の強度低下を小さくできる固相接合方法が注目されており、特に、摩擦発熱現象や金属材の塑性変形を利用した固相接合方法が盛んに検討されている。当該固相接合方法としては、例えば、高速で回転する円柱状のツールを被接合材に圧入して接合する「摩擦攪拌接合（ＦＳＷ）」、回転する円柱状の被接合材を固定された被接合材に当接させて接合する「摩擦圧接」、及び被接合材を当接させた状態で往復運動させて接合する「線形摩擦接合」等が挙げられる。 Attention is being paid to solid-phase bonding methods that can reduce the decrease in strength of joints compared to conventional hot-dip welding, and in particular, solid-phase bonding methods that utilize frictional heat generation and plastic deformation of metal materials are being actively studied. Examples of the solid-state joining method include "friction stirring joining (FSW)" in which a columnar tool rotating at high speed is press-fitted into the material to be joined, and a rotating columnar material to be fixed is fixed. Examples thereof include "friction pressure welding" in which the materials to be joined are brought into contact with each other to be joined, and "linear friction welding" in which the materials to be joined are reciprocated to be joined in a state of being in contact with each other.
　従来の鉄鋼材は溶融溶接の使用を前提とした合金設計となっていることが多いが、近年では摩擦接合法に適した鉄鋼材に関する検討も進められており、例えば、特許文献１（特開２００８－３１４９４号公報）では、低合金構造用鋼であって、６００℃以上の平衡状態においてフェライト単相となる温度域幅とオーステナイト相とフェライト相の２相となる温度域幅の合計が２００℃以上であることを特徴とする摩擦攪拌接合用の低合金構造用鋼、が開示されている。 Conventional steel materials are often alloyed on the premise of using melt welding, but in recent years, studies on steel materials suitable for the friction stir welding method have been promoted. For example, Patent Document 1 (Japanese Patent Laid-Open No. 2008-31494), which is a low alloy structural steel, the total of the temperature range width of a single ferrite phase and the temperature range width of two phases of an austenite phase and a ferrite phase at an equilibrium state of 600 ° C. or higher is 200. A low alloy structural steel for friction stir welding, characterized by a temperature of ° C. or higher, is disclosed.
　上記特許文献１に記載の低合金構造用鋼においては、接合部の到達温度付近における、フェライト単相域及びオーステナイト相‐フェライト２相域を拡大することにより、摩擦攪拌接合における鋼の変形抵抗が大幅に低減し、その結果、回転ツールの耐久性が向上し、接合速度等の接合条件の制限が緩和される、としている。加えて、ツールの損耗、破損による交換作業の頻度が抑えられ、接合時間が短縮されるので施工能率が向上する、としている。 In the low alloy structural steel described in Patent Document 1, the deformation resistance of the steel in friction stir welding is increased by expanding the ferrite single phase region and the austenite phase-ferrite two phase region in the vicinity of the ultimate temperature of the joint. As a result, the durability of the rotating tool is improved, and restrictions on joining conditions such as joining speed are relaxed. In addition, the frequency of replacement work due to wear and tear of the tool is suppressed, and the joining time is shortened, so that the construction efficiency is improved.
　また、摩擦攪拌接合の原理を利用した表面改質技術である摩擦攪拌プロセスに適した鋼に関する検討も進められており、例えば、特許文献２（特開２０１４－１６２９７１号公報）では、質量％で、Ｃ：０．４０～１．５０％、Ｓｉ：０．１５～２．００％、Ｍｎ：０．３０ ～２．００％、Ｃｒ：０．５０～３．００％、残部Ｆｅおよび不可避的不純物からなる摩擦攪拌プロセス用鋼、が開示されている。 Further, studies on steel suitable for the friction stir process, which is a surface modification technique utilizing the principle of friction stir welding, are underway. For example, in Patent Document 2 (Japanese Unexamined Patent Publication No. 2014-162971), the mass is%. , C: 0.40 to 1.50%, Si: 0.15 to 2.00%, Mn: 0.30 to 2.00%, Cr: 0.50 to 3.00%, balance Fe and inevitable A friction stir welding steel consisting of impurities is disclosed.
　上記特許文献２に記載の摩擦攪拌プロセス用鋼においては、摩擦攪拌プロセスを適用することによって優れた表面硬化が達成できる、としている。 It is stated that excellent surface hardening can be achieved by applying the friction stir welding process to the steel for friction stir welding described in Patent Document 2.
　更に、本願発明者も、特許文献３（特開２０１８－１６８６６号公報）において、鋼組成が、質量％で、Ｃ：０．２０～０．４５％、及びＣｒ：１．００～３．５０％を含有し、かつＡ式によって定義される炭素当量ＣＥが０．４０～１．００質量％であること、を特徴とする摩擦攪拌接合用鋼、を開示している。ＣＥ＝Ｃ＋Ｍｎ／６＋（Ｃｕ＋Ｎｉ）／１５＋（Ｃｒ＋Ｍｏ＋Ｖ）／５  ・・・（Ａ）式中に記載された元素記号は、摩擦攪拌接合用鋼材における各成分の含有量を単位質量％で示す。 Further, the inventor of the present application also states in Patent Document 3 (Japanese Unexamined Patent Publication No. 2018-16866) that the steel composition is C: 0.20 to 0.45% and Cr: 1.00 to 3.50 in mass%. Disclosed is a friction stir welding steel, which contains% and has a carbon equivalent CE defined by the formula A of 0.40 to 1.00% by mass. CE = C + Mn / 6 + (Cu + Ni) / 15+ (Cr + Mo + V) / 5 ... The element symbol described in the formula (A) indicates the content of each component in the friction stir welding steel material in unit mass%.
　上記特許文献３に記載の摩擦攪拌接合用鋼においては、摩擦攪拌接合によって従来の高張力鋼と同等以上の継手特性（攪拌部の引張強度及び破壊靭性等）を得ることができる鋼であり、比較的安価な合金元素のみを最小限添加した鋼及び、当該鋼を被接合材とする摩擦攪拌接合方法を提供することができる、としている。 The friction stir welding steel described in Patent Document 3 is a steel capable of obtaining joint characteristics (tensile strength and breaking toughness of the stirring portion, etc.) equal to or higher than those of conventional high-strength steel by friction stir welding. It is said that it is possible to provide a steel to which only a relatively inexpensive alloy element is added to a minimum, and a friction stir welding method using the steel as a material to be welded.
特開２００８－３１４９４号公報Japanese Unexamined Patent Publication No. 2008-31494 特開２０１４－１６２９７１号公報Japanese Unexamined Patent Publication No. 2014-162971 特開２０１８－１６８６６号公報Japanese Unexamined Patent Publication No. 2018-16866
　しかしながら、上記特許文献１に開示されている低合金構造用鋼は、プロセス時の鋼の変形抵抗を低減することで鋼に対する摩擦攪拌接合の適用を容易にするものであり、接合部（攪拌部）の機械的特性や鋼に添加する元素のコストや入手容易性等に関しては殆ど考慮されていない。 However, the low alloy structural steel disclosed in Patent Document 1 facilitates the application of friction stir welding to steel by reducing the deformation resistance of the steel during the process, and the joint portion (stirring portion). ), The cost and availability of elements added to steel are hardly considered.
　また、上記特許文献２に開示されている摩擦攪拌プロセス用鋼は、摩擦熱を利用した表面焼き入れに対して組成を最適化したものであり、接合部の機械的性質を担保することを目的とした鉄鋼材とは、その設計指針が全く異なるものである。 Further, the steel for friction stir welding disclosed in Patent Document 2 has an optimized composition for surface quenching using frictional heat, and an object of ensuring the mechanical properties of the joint. The design guideline is completely different from that of the steel material.
　また、上記特許文献３に開示されている摩擦攪拌接合用鋼では、一般的な高張力鋼と同等以上の継手特性を得ることができるものの、比較的高価なクロム（Ｃｒ）が主要な添加元素として使用されていることに加え、母材及び継手の機械的性質についても更なる高強度化が求められている。近年では引張強度が１０００ＭＰａ以上となる超高張力鋼に対する需要が増加しているところ、上記特許文献３に開示されている摩擦攪拌接合用鋼の引張特性は超高張力鋼の水準には達していない。 Further, in the friction stir welding steel disclosed in Patent Document 3, although joint characteristics equal to or higher than those of general high-strength steel can be obtained, relatively expensive chromium (Cr) is a major additive element. In addition to being used as a base material, the mechanical properties of the base metal and joints are also required to be further increased in strength. In recent years, there has been an increase in demand for ultra-high-strength steel having a tensile strength of 1000 MPa or more, and the tensile properties of the friction stir welding steel disclosed in Patent Document 3 have reached the level of ultra-high-strength steel. No.
　更に、継手の特性を決定するのは全体で最も弱い領域の機械的性質である。一般的には接合部の外縁に形成される熱影響部が軟化することから、当該熱影響部の軟化を抑制することが切望されている。しかしながら、鋼材の高強度化に伴い、熱影響部の軟化を抑制することは極めて困難になってきている。 Furthermore, it is the mechanical properties of the weakest region as a whole that determine the characteristics of the joint. Generally, the heat-affected zone formed on the outer edge of the joint is softened, so that it is desired to suppress the softening of the heat-affected zone. However, as the strength of steel materials increases, it has become extremely difficult to suppress the softening of heat-affected zones.
　以上のような従来技術における問題点に鑑み、本発明の目的は、母材及び固相接合によって得られる継手の引張特性が共に超高張力鋼と同等以上となる鋼であり、比較的安価な合金元素のみを最小限添加した固相接合用鋼及び固相接合用鋼材であって、最小限の合金元素の添加によって熱影響部の軟化が抑制された固相接合用鋼及び固相接合用鋼材を提供することにある。また、本発明は、比較的安価な合金元素のみを最小限添加した固相接合用鋼からなる継手であって、母材及び継手の引張特性が共に超高張力鋼と同等以上である固相接合継手、及び当該継手を有する固相接合構造物を提供することも目的としている。 In view of the above problems in the prior art, an object of the present invention is a steel in which the tensile properties of the base material and the joint obtained by solid-phase bonding are both equal to or higher than those of the ultra-high tension steel, which is relatively inexpensive. Solid-phase bonding steel and solid-phase bonding steel with the minimum amount of alloying elements added, and solid-phase bonding steel and solid-phase bonding in which the softening of heat-affected parts is suppressed by the minimum addition of alloying elements. It is to provide steel materials. Further, the present invention is a joint made of solid-phase bonding steel to which only relatively inexpensive alloying elements are added to a minimum, and the tensile properties of both the base material and the joint are equal to or higher than those of ultra-high tension steel. It is also an object of the present invention to provide a joint and a solid-state joint structure having the joint.
　本発明者は上記目的を達成すべく、鋼の組成及び機械的性質と固相接合によって得られる接合部の組織及び機械的性質との関係について鋭意研究を重ねた結果、炭素鋼を基本としてＳｉ及びＭｎを適量添加すると共に、Ｖ、Ｗ及びＭｏのうちの少なくとも１種を適量含有　　　　させること等が極めて有効であることを見出し、本発明に到達した。 In order to achieve the above object, the present inventor has conducted extensive research on the relationship between the composition and mechanical properties of steel and the structure and mechanical properties of the joint obtained by solid-phase bonding. As a result, Si is based on carbon steel. And Mn were added in appropriate amounts, and at least one of V, W and Mo was contained in an appropriate amount, and the like was found to be extremely effective, and the present invention was reached.
　即ち、本発明は、
　鋼組成が、質量％で、
　Ｃ：０．２０～２．１４％、
　ＳｉとＡｌの合計：１．００～３．００％、
　Ｍｎ：２．００～５．００％、を含有すると共に、
　Ｖ：０．１％超３．０％以下、Ｗ：１．０％超６．０％以下、Ｍｏ：１．０％超６．０％以下、のうちの少なくとも１種を含有し、
　残部がＦｅ及び不可避不純物のみの組成であること、
　を特徴とする固相接合用鋼、を提供する。 That is, the present invention
Steel composition by mass%
C: 0.20 to 2.14%,
Total of Si and Al: 1.00 to 3.00%,
Mn: 2.00 to 5.00%, and
It contains at least one of V: more than 0.1% and 3.0% or less, W: more than 1.0% and 6.0% or less, and Mo: more than 1.0% and 6.0% or less.
The balance is composed of Fe and unavoidable impurities only.
Provided is a steel for solid phase bonding, which is characterized by the above.
　本発明の固相接合用鋼は比較的大量の炭素を含有することで高強度化が図られている一方、溶融溶接と比較して接合温度が低いことに加えて冷却速度を遅くすることができる固相接合の使用を前提とすることで、割れや欠陥等の存在しない良好な接合部を得ることができる。ここで、炭素含有量を０．２０質量％以上とすることで鋼及び固相接合部の強度を十分に向上させることができ、２．１４質量％以下とすることで黒鉛の分散による引張特性の低下を抑制することができる。 While the solid-phase bonding steel of the present invention has been improved in strength by containing a relatively large amount of carbon, the bonding temperature can be lowered and the cooling rate can be slowed down as compared with melt welding. By assuming the use of a solid phase weld that can be formed, a good joint portion without cracks or defects can be obtained. Here, by setting the carbon content to 0.20% by mass or more, the strength of the steel and the solid phase joint can be sufficiently improved, and by setting it to 2.14% by mass or less, the tensile properties due to the dispersion of graphite. Can be suppressed.
　炭素含有量は０．２０～０．４５質量％であることが好ましく、０．２０～０．３０質量％であることがより好ましく、０．２０～０．２５質量％であることが最も好ましい。本発明の固相接合用鋼においては、炭素含有量の下限である０．２０質量％で母材及び固相接合部の引張強度が１０００ＭＰａ以上となることから、良好な延性を担保するために、所望の引張強度が得られる限りにおいて、上限値は小さな値とすることが好ましい。 The carbon content is preferably 0.20 to 0.45% by mass, more preferably 0.20 to 0.30% by mass, and most preferably 0.20 to 0.25% by mass. .. In the solid-phase bonding steel of the present invention, the tensile strength of the base metal and the solid-phase bonding portion is 1000 MPa or more at 0.20% by mass, which is the lower limit of the carbon content, so that good ductility can be ensured. The upper limit is preferably a small value as long as the desired tensile strength can be obtained.
　また、ＳｉとＡｌは同様の効果を有し、Ｓｉ及び／又はＡｌは、主として母材及び固相接合部の延性を担保する目的で添加されている。ＳｉとＡｌの含有量の合計を１．００質量％以上とすることで、延性を低下させるセメンタイトの生成を抑制したり、オーステナイトを安定化することができる。一方で、３．００質量％以上添加しても当該効果は向上しないため、添加量の上限を３．００質量％としている。ＳｉとＡｌの含有量の合計は１．５０～２．５０質量％とすることが好ましく、１．７５～２．２５質量％とすることがより好ましい。なお、Ｓｉ及びＡｌは安価な合金元素であり、豊富に存在する元素である。また、ＳｉとＡｌと共に添加する必要はなく、どちらか一方を添加してもよい。 Further, Si and Al have the same effect, and Si and / or Al are added mainly for the purpose of ensuring the ductility of the base metal and the solid phase joint. By setting the total content of Si and Al to 1.00% by mass or more, it is possible to suppress the formation of cementite that lowers ductility and stabilize austenite. On the other hand, since the effect is not improved even if 3.00% by mass or more is added, the upper limit of the addition amount is set to 3.00% by mass. The total content of Si and Al is preferably 1.50 to 2.50% by mass, and more preferably 1.75 to 2.25% by mass. In addition, Si and Al are inexpensive alloying elements and are abundant elements. Further, it is not necessary to add Si and Al together, and either one may be added.
　また、Ｍｎの添加も母材及び固相接合部の延性向上に寄与している。上記のＳｉの添加に加えてＭｎの含有量を２．００質量％以上とすることで、オーステナイト安定化によるＴＲＩＰ（マルテンサイト変態誘起塑性）効果による延性の向上が期待できる。加えて、固相接合の条件にも依存するが、２．００質量％以上のＭｎを添加することで焼き入れ性を維持し、かつ固相接合部のオーステナイト粒径を微細化し、その結果オーステナイトから微細なラス状のマルテンサイト組織を形成させることができる。その結果、高強度でありつつ十分な延性を有する固相接合部を得ることができる。一方で、当該効果はＭｎの含有量を５．００質量％以上としても殆ど向上しないことから、Ｍｎ含有量の上限を５．００質量％としている。ここで、強度を重視する場合はＭｎ含有量を３．００～５．００質量％とすることが好ましく、延性を重視する場合は２．００質量％以上３．００質量％未満とすることが好ましい。 The addition of Mn also contributes to the improvement of ductility of the base metal and solid phase joint. By setting the Mn content to 2.00% by mass or more in addition to the above-mentioned addition of Si, improvement in ductility due to the TRIP (martensite transformation-induced plasticity) effect due to austenite stabilization can be expected. In addition, although it depends on the conditions of solid phase bonding, by adding 2.00% by mass or more of Mn, quenchability is maintained and the austenite particle size of the solid phase bonding portion is made finer, resulting in austenite. It is possible to form a fine lath-shaped martensite structure from the material. As a result, a solid phase joint having high strength and sufficient ductility can be obtained. On the other hand, since the effect is hardly improved even if the Mn content is 5.00% by mass or more, the upper limit of the Mn content is set to 5.00% by mass. Here, when strength is important, the Mn content is preferably 3.00 to 5.00% by mass, and when ductility is important, it is 2.00% by mass or more and less than 3.00% by mass. preferable.
　また、本発明の固相接合用鋼は、Ｖ：０．１％超３．０％以下、Ｗ：１．０％超６．０％以下、Ｍｏ：１．０％超６．０％以下、のうちの少なくとも１種を含有することで、これらを含む二次炭化物が生成し、固相接合によって形成される熱影響部の硬度低下を抑制することができる。ここで、二次炭化物を生成する合金元素は他にも存在するが、Ｖ、Ｗ及びＭｏは適度な炭化物生成傾向を有しており、固相接合部の外縁における熱影響部の温度履歴によって効率的に二次炭化物が生成され、当該領域の硬度低下を極めて効果的に抑制することができる。なお、一般的に知られている各合金元素の炭化物生成傾向は、Ｔｉ＞Ｔａ＞Ｎｂ＞Ｖ＞Ｗ＞Ｍｏ＞Ｃｒ＞Ｍｎ＞（Ｆｅ）＞Ｎｉ，Ｃｏ，Ａｌ，Ｓｉとなっている。Ｔｉ、Ｔａ及びＮｂは炭化物生成傾向が強過ぎるため、例えば、オーステナイト中にも容易に炭化物を生成し、熱影響部に生成する二次炭化物量が低下するため、熱影響部を効果的に二次硬化させることができない。一方で、Ｃｒ及びＭｎは炭化物生成傾向が弱過ぎることに加え、炭化物の硬度も比較的低いため、熱影響部を効果的に二次硬化させることができない。 Further, the solid-state bonding steel of the present invention has V: more than 0.1% and 3.0% or less, W: more than 1.0% and 6.0% or less, and Mo: more than 1.0% and 6.0% or less. By containing at least one of the above, secondary carbides containing these are generated, and the decrease in hardness of the heat-affected zone formed by solid-phase bonding can be suppressed. Here, although there are other alloying elements that form secondary carbides, V, W, and Mo have an appropriate tendency to form carbides, and the temperature history of the heat-affected zone at the outer edge of the solid-phase junction Secondary carbides are efficiently produced, and the decrease in hardness of the region can be suppressed extremely effectively. The generally known tendency of each alloying element to form carbides is Ti> Ta> Nb> V> W> Mo> Cr> Mn> (Fe)> Ni, Co, Al, Si. Since Ti, Ta and Nb have a too strong tendency to form carbides, for example, carbides are easily generated even in austenite, and the amount of secondary carbides generated in the heat-affected zone decreases, so that the heat-affected zone can be effectively divided. Cannot be next cured. On the other hand, Cr and Mn have a too weak tendency to form carbides, and the hardness of the carbides is also relatively low, so that the heat-affected zone cannot be effectively secondary-cured.
　ここで、本発明の固相接合用鋼においては、Ｍｏを１．０％超６．０％以下添加することが好ましく、Ｍｏを２．０％超４．０％以下添加することがより好ましい。Ｍｏを添加することによって、ＶやＷを添加する場合よりも顕著な二次硬化を熱影響部に発現させることができる。 Here, in the solid phase bonding steel of the present invention, it is preferable to add Mo in an amount of more than 1.0% and 6.0% or less, and more preferably Mo is added in an amount of more than 2.0% and 4.0% or less. .. By adding Mo, it is possible to develop a remarkable secondary curing in the heat-affected zone as compared with the case of adding V or W.
　本発明の固相接合用鋼は、上記の元素以外の残部がＦｅ及び不可避不純物のみの組成となっている。炭素鋼を基本とし、レアメタルの添加を控えることで製造コストを低減することができることに加え、生産の持続可能性を担保（偏在リスクを低減）することができる。なお、本発明の固相接合用鋼は固相接合による接合を前提としているが、当該固相接合の方法は本発明の効果を損なわない限りにおいて特に限定されず、従来公知の種々の固相接合方法を使用することができる。代表的な固相接合方法としては、摩擦攪拌接合、摩擦接合及び線形摩擦接合を挙げることができる。 The solid-phase bonding steel of the present invention has a composition in which the balance other than the above elements is only Fe and unavoidable impurities. In addition to being able to reduce manufacturing costs by refraining from adding rare metals based on carbon steel, it is possible to ensure the sustainability of production (reduce the risk of uneven distribution). The steel for solid phase bonding of the present invention is premised on bonding by solid phase bonding, but the method of solid phase bonding is not particularly limited as long as the effect of the present invention is not impaired, and various conventionally known solid phases are used. A joining method can be used. Typical solid phase bonding methods include friction stir welding, friction bonding and linear friction bonding.
　また、本発明は、上記本発明の固相接合用鋼からなる固相接合用鋼材が少なくとも一方の被接合材となっており、前記固相接合用鋼材の固相接合部が微細なラス状のマルテンサイト組織を有し、前記マルテンサイト組織における旧オーステナイトの平均粒径が１５μｍ以下であること、を特徴とする固相接合継手も提供する。 Further, in the present invention, the solid-phase bonding steel material made of the solid-phase bonding steel of the present invention is at least one material to be bonded, and the solid-phase bonding portion of the solid-phase bonding steel material has a fine lath shape. Also provided is a solid phase joint having the martensite structure of the above, wherein the average particle size of the former austenite in the martensite structure is 15 μm or less.
　本発明の固相接合継手は被接合材の少なくとも一方が本発明の固相接合用鋼であり、高価な合金元素の添加が最小限となっており比較的安価であることに加え、高い強度と延性を兼ね備えている。また、接合部の組織がラス状のマルテンサイトとなっており、当該領域の炭素含有量が０．２０～２．１４％となっていることから、接合部は極めて高い引張強度を有している。加えて、Ｍｎの添加によりマルテンサイトが微細化されており、接合条件によっては残留オーステナイトに起因するＴＲＩＰ効果も期待できることから、良好な延性を発現することができる。 In the solid-phase joint of the present invention, at least one of the materials to be joined is the steel for solid-phase bonding of the present invention, and the addition of expensive alloying elements is minimized, which is relatively inexpensive and has high strength. And ductility. Further, since the structure of the joint is lath-shaped martensite and the carbon content of the region is 0.20 to 2.14%, the joint has extremely high tensile strength. There is. In addition, martensite is refined by the addition of Mn, and a TRIP effect due to retained austenite can be expected depending on the joining conditions, so that good ductility can be exhibited.
　本発明の固相接合継手においては、前記マルテンサイト組織における旧オーステナイトの平均粒径が１５μｍ以下となっている。旧オーステナイト組織を微細化することで、ラス状のマルテンサイト組織が微細化され、固相接合部に高い強度と延性を付与することができる。ここで、旧オーステナイトの平均粒径は１０μｍ以下であることがより好ましく、５μｍ以下であることが最も好ましい。本発明の固相接合継手においては、Ｖ、Ｗ及びＭｏのうちの少なくとも１種が添加されているが、当該添加は旧オーステナイト粒径を低減させる効果も有している。なお、旧オーステナイトの平均粒径を求める方法は特に限定されず従来公知の種々の方法を用いることができるが、例えば、適当なエッチングを施した組織を観察してもよく、マルテンサイトと旧オーステナイトとの方位関係により、マルテンサイトから旧オーステナイトを再構築し、再構築した旧オーステナイト組織から求めてもよい。 In the solid phase joint of the present invention, the average particle size of the former austenite in the martensite structure is 15 μm or less. By refining the old austenite structure, the lath-shaped martensite structure is miniaturized, and high strength and ductility can be imparted to the solid-phase junction. Here, the average particle size of the old austenite is more preferably 10 μm or less, and most preferably 5 μm or less. In the solid phase joint of the present invention, at least one of V, W and Mo is added, and the addition also has an effect of reducing the particle size of the old austenite. The method for determining the average particle size of the former austenite is not particularly limited, and various conventionally known methods can be used. For example, a structure subjected to appropriate etching may be observed, and martensite and the former austenite may be observed. Depending on the orientation relationship with, the former austenite may be reconstructed from martensite and obtained from the reconstructed former austenite organization.
　また、本発明の固相接合継手は、前記固相接合用鋼材のビッカース硬度が４００ＨＶ以上、前記固相接合部のビッカース硬度が４００ＨＶ以上、前記固相接合部近傍の熱影響部のビッカース硬度が４００ＨＶ以上、であること、が好ましい。より好ましいビッカース硬度は、固相接合用鋼材、固相接合部及び熱影響部共に４５０ＨＶ以上である。ここで、鋼材のビッカース硬度が４００ＨＶの場合は引張強度が約１２００ＭＰａとなり、ビッカース硬度が４５０ＨＶの場合は引張強度が約１３５０ＭＰａとなる。 Further, in the solid phase joint of the present invention, the Vickers hardness of the solid phase bonding steel material is 400 HV or more, the Vickers hardness of the solid phase joint is 400 HV or more, and the Vickers hardness of the heat affected zone in the vicinity of the solid phase joint is 400 HV or more. It is preferably 400 HV or more. A more preferable Vickers hardness is 450 HV or more for the steel material for solid phase bonding, the solid phase bonding portion, and the heat-affected zone. Here, when the Vickers hardness of the steel material is 400 HV, the tensile strength is about 1200 MPa, and when the Vickers hardness of the steel material is 450 HV, the tensile strength is about 1350 MPa.
　また、本発明の固相接合継手は、前記固相接合部及び前記熱影響部のビッカース硬度が、前記固相接合用鋼材のビッカース硬度の８０～１２０％の値となること、が好ましい。固相接合用鋼材、固相接合部及び熱影響部の強化機構は同一ではないが、結果としてこれらの硬度のばらつきを低減することで、機械的性質に特異領域のない良好な継手とすることができる。 Further, in the solid phase joint of the present invention, it is preferable that the Vickers hardness of the solid phase joint and the heat affected zone is 80 to 120% of the Vickers hardness of the steel material for solid phase bonding. The strengthening mechanism of the steel material for solid phase bonding, the solid phase joint and the heat-affected zone is not the same, but as a result, by reducing the variation in hardness, a good joint with no peculiar region in mechanical properties should be obtained. Can be done.
　また、本発明の固相接合継手は、前記熱影響部にＶ、Ｗ及びＭｏのうちの少なくとも１種を含む二次炭化物を有すること、が好ましい。継手全体の硬度分布を均質化するためには熱影響部の硬度低下を抑制する必要があるが、当該領域に高硬度の二次炭化物を分散させることにより、極めて効果的に軟化を抑制することができる。 Further, it is preferable that the solid phase joint of the present invention has a secondary carbide containing at least one of V, W and Mo in the heat-affected zone. In order to homogenize the hardness distribution of the entire joint, it is necessary to suppress the decrease in hardness of the heat-affected zone, but by dispersing high-hardness secondary carbides in the region, softening can be suppressed extremely effectively. Can be done.
　また、本発明の固相接合継手は、室温での引張強さが１０００ＭＰａ以上、伸びが２０％以上であることが好ましく、１２００ＭＰａ以上、伸びが２０％以上であることがより好ましく、１５００ＭＰａ以上、伸びが２０％以上であることが最も好ましい。母材と固相接合部に高い引張特性を付与すると共に、熱影響部での軟化を抑制することで、これらの値を実現することができる。固相接合継手がこれらの引張特性を有することで、高い強度と信頼性が要求される用途において、超高張力鋼と同等以上の機械的性質を有する継手として十分に使用することができる。ここで、引張試験の結果は引張試験片のサイズ及び形状の影響を受ける場合が存在するが、本願明細書においては、平行部の長さが４ｍｍ、幅が２ｍｍ程度の、比較的小型の引張試験片を用いて得られた値を基準とする。 Further, the solid phase joint of the present invention preferably has a tensile strength of 1000 MPa or more and an elongation of 20% or more at room temperature, more preferably 1200 MPa or more and an elongation of 20% or more, 1500 MPa or more. Most preferably, the elongation is 20% or more. These values can be achieved by imparting high tensile properties to the base metal and the solid phase joint and suppressing softening in the heat-affected zone. Since the solid-phase joint has these tensile properties, it can be sufficiently used as a joint having mechanical properties equal to or higher than those of ultra-high-strength steel in applications requiring high strength and reliability. Here, the result of the tensile test may be affected by the size and shape of the tensile test piece, but in the present specification, a relatively small tensile strength having a parallel portion having a length of 4 mm and a width of about 2 mm. The value obtained using the test piece is used as a reference.
　また、本発明の固相接合継手は、前記固相接合部が摩擦攪拌接合部であること、が好ましい。固相接合部は摩擦接合や線形摩擦接合によって形成されたものでもよいが、摩擦攪拌接合部とすることで、鋼板の任意の領域に固相接合部を形成することができ、大型構造物の製造にも対応することができる。 Further, in the solid phase joint of the present invention, it is preferable that the solid phase joint is a friction stir weld. The solid phase joint may be formed by friction welding or linear friction welding, but by using a friction stir welding joint, a solid phase joint can be formed in any region of the steel sheet, and a large structure can be formed. It can also be used for manufacturing.
　また、本発明は、本発明の固相接合継手を有すること、を特徴とする固相接合構造物、も提供する。固相接合継手以外の構造部に関する材質、形状及びサイズは特に限定されず、従来公知の種々の構造物とすることができる。 The present invention also provides a solid phase bonding structure characterized by having the solid phase bonding joint of the present invention. The material, shape, and size of the structural part other than the solid-phase joint are not particularly limited, and various conventionally known structures can be used.
　更に、本発明は、本発明の固相接合用鋼からなり、ラス状のマルテンサイト組織を有し、前記マルテンサイト組織における旧オーステナイトの平均粒径が１５μｍ以下であること、を特徴とする固相接合用鋼材、も提供する。当該組成及び組織を有する固相接合用鋼材は、室温での引張強さが１０００ＭＰａ以上、伸びが２０％以上となり、高い強度と信頼性が要求される用途において、超高張力鋼と同等以上の機械的性質を有する鋼材として十分に使用することができる Further, the present invention is characterized in that it is made of the solid phase bonding steel of the present invention, has a lath-shaped martensite structure, and the average particle size of the former austenite in the martensite structure is 15 μm or less. We also provide steel materials for phase bonding. The solid-phase bonding steel material having the composition and structure has a tensile strength of 1000 MPa or more and an elongation of 20% or more at room temperature, which is equal to or higher than that of ultra-high-strength steel in applications requiring high strength and reliability. Can be sufficiently used as a steel material having mechanical properties
　本発明によれば、母材及び固相接合によって得られる継手の引張特性が共に超高張力鋼と同等以上となる鋼であり、比較的安価な合金元素のみを最小限添加した固相接合用鋼及び固相接合用鋼材であって、最小限の合金元素の添加によって熱影響部の軟化が抑制された固相接合用鋼及び固相接合用鋼材を提供することができる。また、本発明によれば、比較的安価な合金元素のみを最小限添加した固相接合用鋼からなる継手であって、母材及び継手の引張特性が共に超高張力鋼と同等以上である固相接合継手、及び当該継手を有する固相接合構造物を提供することもできる。 According to the present invention, the tensile properties of the base metal and the joint obtained by solid-phase bonding are both equal to or higher than those of ultra-high-strength steel, and for solid-phase bonding to which only relatively inexpensive alloying elements are added to a minimum. It is possible to provide a steel material for solid-phase bonding and a steel material for solid-phase bonding in which softening of a heat-affected portion is suppressed by adding a minimum amount of alloying elements. Further, according to the present invention, the joint is made of solid-phase bonding steel to which only relatively inexpensive alloying elements are added to a minimum, and the tensile properties of both the base material and the joint are equal to or higher than those of ultra-high-strength steel. It is also possible to provide a solid phase joint and a solid phase joint structure having the joint.
摩擦攪拌接合によって形成された固相接合部を有する固相接合継手の概略図である。It is a schematic diagram of the solid-phase joint having the solid-phase joint formed by friction stir welding. 摩擦圧接によって形成された固相接合部を有する固相接合継手の概略図である。It is a schematic diagram of the solid-phase joint having the solid-phase joint formed by friction welding. 線形摩擦接合によって形成された固相接合部を有する固相接合継手の概略図である。It is the schematic of the solid-phase joint having the solid-phase joint formed by the linear friction joint. 実施固相接合用鋼２、実施固相接合用鋼３及び比較固相接合用鋼１の母材及び攪拌部の組織観察結果である。It is the structure observation result of the base material and the stirring part of the implementation solid phase bonding steel 2, the implementation solid phase bonding steel 3 and the comparative solid phase bonding steel 1. 実施固相接合用鋼３の母材、攪拌部及び熱影響部の組織観察結果である。It is the result of observing the structure of the base material, the stirring part and the heat-affected zone of the solid-phase bonding steel 3. 母材及び攪拌部のマルテンサイトから旧オーステナイトを再構築した結果である。This is the result of reconstructing the old austenite from the martensite of the base material and the stirring part. 実施固相接合用鋼１、比較固相接合用鋼１、比較固相接合用鋼２及び比較固相接合用鋼３の摩擦攪拌接合継手の接合部横断面におけるビッカース硬度分布である。It is a Vickers hardness distribution in the cross section of the joint portion of the friction stir welding joint of the implementation solid phase bonding steel 1, the comparative solid phase bonding steel 1, the comparative solid phase bonding steel 2, and the comparative solid phase bonding steel 3. 実施固相接合用鋼２、実施固相接合用鋼３、実施固相接合用鋼４及び比較固相接合用鋼１の摩擦攪拌接合継手の接合部横断面におけるビッカース硬度分布である。It is a Vickers hardness distribution in the cross section of the joint portion of the friction stir welding joint of the steel 2 for solid phase welding, the steel 3 for solid phase bonding, the steel 4 for solid phase bonding, and the steel 1 for comparative solid phase welding.
　以下、本発明の固相接合用鋼、固相接合用鋼材、固相接合継手及び固相接合構造物の代表的な実施形態について詳細に説明するが、本発明はこれらのみに限定されるものではない。なお、以下の説明では、重複する説明は省略する場合がある。 Hereinafter, typical embodiments of the solid phase bonding steel, the solid phase bonding steel material, the solid phase bonding joint, and the solid phase bonding structure of the present invention will be described in detail, but the present invention is limited to these. is not it. In the following description, duplicate description may be omitted.
（１）固相接合用鋼
　本発明の固相接合用鋼は、
　鋼組成が、質量％で、
　Ｃ：０．２０～２．１４％、
　ＳｉとＡｌの合計：１．００～３．００％、
　Ｍｎ：２．００～５．００％、を含有すると共に、
　Ｖ：０．１％超３．０％以下、Ｗ：１．０％超６．０％以下、Ｍｏ：１．０％超６．０％以下、のうちの少なくとも１種を含有し、
　残部がＦｅ及び不可避不純物のみの組成であること、
　を特徴とする固相接合用鋼、である。 (1) Steel for solid phase bonding The steel for solid phase bonding of the present invention is
Steel composition by mass%
C: 0.20 to 2.14%,
Total of Si and Al: 1.00 to 3.00%,
Mn: 2.00 to 5.00%, and
It contains at least one of V: more than 0.1% and 3.0% or less, W: more than 1.0% and 6.0% or less, and Mo: more than 1.0% and 6.0% or less.
The balance is composed of Fe and unavoidable impurities only.
It is a solid phase bonding steel.
　構造材の比強度の向上が切望されているところ、鋼についてはレアメタルの添加による各種高張力鋼が提案されているが、レアメタルは偏在リスクが高く、コストや生産安定性等の観点から問題となる。一方で、鋼の強度は基本的に炭素量の増加に伴って向上することから、炭素鋼を積極的に活用することができればレアメタルの使用量を削減することができる。 Since there is an urgent need to improve the specific strength of structural materials, various high-strength steels have been proposed by adding rare metals, but rare metals have a high risk of uneven distribution, which poses a problem from the viewpoint of cost and production stability. Become. On the other hand, since the strength of steel basically increases as the amount of carbon increases, the amount of rare metals used can be reduced if carbon steel can be actively utilized.
　ここで、炭素量が多い中・高炭素鋼は溶融溶接時に割れが発生するため、溶接が極めて困難な材料であるとされているが、本発明の固相接合用鋼は固相接合の使用を前提とすることで当該問題を克服している。また、適量のＳｉ、Ａｌ及びＭｎの添加により、母材及び接合部に良好な延性が付与されている。更に、Ｖ、Ｗ及びＭｏのうちの少なくとも１種を添加することで、これらを含む二次炭化物が生成し、熱影響部の硬度低下が抑制される。以下、各成分について詳細に説明する。 Here, medium- and high-carbon steels with a large amount of carbon are considered to be extremely difficult to weld because cracks occur during melt welding. However, the steel for solid-phase welding of the present invention uses solid-state bonding. The problem is overcome by assuming that. Further, by adding an appropriate amount of Si, Al and Mn, good ductility is imparted to the base material and the joint portion. Further, by adding at least one of V, W and Mo, secondary carbides containing these are generated, and the decrease in hardness of the heat-affected zone is suppressed. Hereinafter, each component will be described in detail.
１．必須の添加元素
　Ｃ：０．２０～２．１４質量％
　炭素含有量を０．２０質量％以上とすることで鋼及び固相接合部の強度を十分に向上させることができ、２．１４質量％以下とすることで黒鉛の分散による引張特性の低下を抑制することができる。炭素含有量は０．２０～０．４５質量％であることが好ましく、０．２０～０．３０質量％であることがより好ましく、０．２０～０．２５質量％であることが最も好ましい。本発明の固相接合用鋼においては、炭素含有量の下限である０．２０質量％で母材及び固相接合部の引張強度が１０００ＭＰａ以上となることから、良好な延性を担保するために、所望の引張強度が得られる限りにおいて、上限値は小さな値とすることが好ましい。 1. 1. Essential additive element C: 0.20 to 2.14% by mass
By setting the carbon content to 0.20% by mass or more, the strength of the steel and solid phase joints can be sufficiently improved, and by setting it to 2.14% by mass or less, the tensile properties are deteriorated due to the dispersion of graphite. It can be suppressed. The carbon content is preferably 0.20 to 0.45% by mass, more preferably 0.20 to 0.30% by mass, and most preferably 0.20 to 0.25% by mass. .. In the solid-phase bonding steel of the present invention, the tensile strength of the base metal and the solid-phase bonding portion is 1000 MPa or more at 0.20% by mass, which is the lower limit of the carbon content, so that good ductility can be ensured. The upper limit is preferably a small value as long as the desired tensile strength can be obtained.
　ＳｉとＡｌの合計：１．００～３．００質量％
　Ｓｉ及び／又はＡｌの含有量の合計を１．００質量％以上とすることで、延性を低下させるセメンタイトの生成を抑制することができる。一方で、３．００質量％以上添加しても当該効果は向上しないため、添加量の上限を３．００質量％としている。Ｓｉ及び／又はＡｌの含有量の合計は１．５０～２．５０質量％とすることが好ましく、１．７５～２．２５質量％とすることがより好ましい。 Total of Si and Al: 1.00 to 3.00% by mass
By setting the total content of Si and / or Al to 1.00% by mass or more, the formation of cementite that reduces ductility can be suppressed. On the other hand, since the effect is not improved even if 3.00% by mass or more is added, the upper limit of the addition amount is set to 3.00% by mass. The total content of Si and / or Al is preferably 1.50 to 2.50% by mass, and more preferably 1.75 to 2.25% by mass.
　Ｍｎ：２．００～５．００質量％
　Ｓｉの添加に加えてＭｎの含有量を２．００質量％以上とすることで、オーステナイト安定化によるＴＲＩＰ（マルテンサイト変態誘起塑性）効果による延性の向上が期待できる。加えて、固相接合の条件にも依存するが、２．００質量％以上のＭｎを添加することで固相接合部に微細なマルテンサイト組織を形成させることができる。その結果、高強度でありつつ十分な延性を有する固相接合部を得ることができる。一方で、当該効果はＭｎの含有量を５．００質量％以上としても殆ど向上しないことから、Ｍｎ含有量の上限を５．００質量％としている。ここで、強度を重視する場合はＭｎ含有量を３．００～５．００質量％とすることが好ましく、延性を重視する場合は２．００質量％以上３．００質量％未満とすることが好ましい。 Mn: 2.00 to 5.00 mass%
By setting the Mn content to 2.00% by mass or more in addition to the addition of Si, it is expected that the ductility will be improved by the TRIP (martensite transformation-induced plasticity) effect due to the stabilization of austenite. In addition, although it depends on the conditions of solid phase bonding, a fine martensite structure can be formed in the solid phase bonding portion by adding 2.00% by mass or more of Mn. As a result, a solid phase joint having high strength and sufficient ductility can be obtained. On the other hand, since the effect is hardly improved even if the Mn content is 5.00% by mass or more, the upper limit of the Mn content is set to 5.00% by mass. Here, when strength is important, the Mn content is preferably 3.00 to 5.00% by mass, and when ductility is important, it is 2.00% by mass or more and less than 3.00% by mass. preferable.
　Ｖ、Ｗ及びＭｏのうちの少なくとも１種
　Ｖ：０．１％超３．０％以下
　Ｖを０．１％超添加することで、固相接合継手の熱影響部に軟化を抑制する程度の二次炭化物を生成させることができる。一方で、３．０％を超えてＶを添加してもこれによる効果は飽和することに加え、マトリックス中に固溶できなかったＶによって固相接合継手の機械的性質が低下する虞がある。加えて、経済的観点からも好ましくない。Ｖのより好ましい添加量は０．２５～０．７５％である。 At least one of V, W and Mo V: More than 0.1% 3.0% or less By adding more than 0.1% V, softening is suppressed in the heat-affected zone of the solid-phase joint. Secondary carbides can be produced. On the other hand, even if V is added in excess of 3.0%, the effect of this is saturated, and V that cannot be solid-solved in the matrix may deteriorate the mechanical properties of the solid-phase joint. .. In addition, it is not preferable from an economic point of view. A more preferable amount of V added is 0.25 to 0.75%.
　Ｗ：１．０％超６．０％以下
　Ｗを１．０％超添加することで、固相接合継手の熱影響部に軟化を抑制する程度の二次炭化物を生成させることができる。一方で、６．０％を超えてＷを添加してもこれによる効果は飽和することに加え、マトリックス中に固溶できなかったＷによって固相接合継手の機械的性質が低下する虞がある。加えて、経済的観点からも好ましくない。Ｗのより好ましい添加量は２．０～４．０％である。 W: More than 1.0% 6.0% or less By adding more than 1.0% W, secondary carbides that suppress softening can be generated in the heat-affected zone of the solid-phase joint. On the other hand, even if W is added in excess of 6.0%, the effect of this is saturated, and W that cannot be solid-solved in the matrix may deteriorate the mechanical properties of the solid-phase joint. .. In addition, it is not preferable from an economic point of view. A more preferable amount of W added is 2.0 to 4.0%.
　Ｍｏ：１．０％超６．０％以下
　Ｍｏを１．０％超添加することで、固相接合継手の熱影響部に軟化を抑制する程度の二次炭化物を生成させることができる。一方で、６．０％を超えてＭｏを添加してもこれによる効果は飽和することに加え、マトリックス中に固溶できなかったＭｏによって固相接合継手の機械的性質が低下する虞がある。加えて、経済的観点からも好ましくない。Ｍｏのより好ましい添加量は２．０～４．０％である。 Mo: More than 1.0% 6.0% or less By adding more than 1.0% of Mo, secondary carbides that suppress softening can be generated in the heat-affected zone of the solid-phase joint. On the other hand, even if Mo is added in excess of 6.0%, the effect of this is saturated, and Mo that cannot be solid-solved in the matrix may deteriorate the mechanical properties of the solid-phase joint. .. In addition, it is not preferable from an economic point of view. A more preferable amount of Mo added is 2.0 to 4.0%.
　Ｖ、Ｗ及びＭｏのうち、最も好ましい添加元素はＭｏである。また、これらの元素は１種のみを添加してもよく、複数添加してもよい。ここで、複数種を添加する場合は、炭化物を形成するための炭素含有量を勘案して、添加量が過剰にならないように留意することが好ましい。 Of V, W and Mo, the most preferable additive element is Mo. Further, only one of these elements may be added, or a plurality of these elements may be added. Here, when a plurality of types are added, it is preferable to take care not to make the addition amount excessive in consideration of the carbon content for forming the carbide.
２．任意の添加元素
　Ｃｒ：１．００～３．５０質量％
適当な量のＣｒを含有することで、固相接合部の強度及び靭性を改善することができる。靭性は強度と延性の一種の積であるため、Ｃｒの添加により強度と延性が共に高くなる結果、靭性が改善される。Ｃｒの添加による固相接合部の特性改善のメカニズムは必ずしも明らかにはなっていないが、炭素鋼にＣｒを添加することにより、固相接合中（オーステナイトからの冷却過程）における初析フェライトの生成が抑制され、得られる固相接合部の強度が上昇すると共に、マルテンサイト（又はベイナイト）の延性が向上するものと思われる。なお、Ｃｒのより好ましい含有量は１．５０～３．００質量％である。 2. Optional additive element Cr: 1.00 to 3.50% by mass
By containing an appropriate amount of Cr, the strength and toughness of the solid phase joint can be improved. Since toughness is a kind of product of strength and ductility, the addition of Cr increases both strength and ductility, resulting in improved toughness. Although the mechanism of improving the characteristics of the solid-phase junction by adding Cr has not been clarified, the addition of Cr to carbon steel produces ductile ferrite during solid-phase bonding (cooling process from austenite). Is suppressed, the strength of the obtained solid-phase junction is increased, and the ductility of martensite (or bainite) is considered to be improved. The more preferable content of Cr is 1.50 to 3.00% by mass.
　Ｃｕ：３．０質量％以下
　Ｃｕは、母材の強度を確保するために有用な元素であるが、３．０質量％を超えて含有すると母材及びＨＡＺ部が硬化するため、３．０質量％以下とすることが好ましい。 Cu: 3.0% by mass or less Cu is an element useful for ensuring the strength of the base material, but if it is contained in excess of 3.0% by mass, the base material and the HAZ portion are cured, so 3.0. It is preferably mass% or less.
　Ｎｉ：５．０質量％以下
　Ｎｉは、母材の強度と靱性を向上させる元素であるが、５．０質量％を超えて含有するとＨＡＺ部が硬化するため、５．０質量％以下とすることが好ましい。また、Ｎｉは高価であることからも、５．０質量％以下とすることが好ましい。 Ni: 5.0% by mass or less Ni is an element that improves the strength and toughness of the base metal, but if it is contained in excess of 5.0% by mass, the HAZ portion will harden, so it should be 5.0% by mass or less. Is preferable. Further, since Ni is expensive, it is preferably 5.0% by mass or less.
　Ｎｂ：０．１質量％以下
　Ｎｂは、母材およびＨＡＺ部の強度と靱性を確保するために有用な元素であるが、０．１質量％を超えると靱性に悪影響を及ぼすことから、０．１質量％以下とすることが好ましい。また、Ｎｂは高価であることからも、０．１質量％以下とすることが好ましい。なお、Ｎｂはオーステナイトを微細化し、その結果、微細なラス状のマルテンサイト組織を形成する効果を有すると考えられる。 Nb: 0.1% by mass or less Nb is an element useful for ensuring the strength and toughness of the base material and the HAZ portion, but if it exceeds 0.1% by mass, it adversely affects the toughness. It is preferably 1% by mass or less. Further, since Nb is expensive, it is preferably 0.1% by mass or less. It is considered that Nb has the effect of refining austenite and, as a result, forming a fine lath-like martensite structure.
　Ｔｉ：０．１質量％以下
　Ｔｉは、母材およびＨＡＺ部の強度と靱性を確保するために有用な元素であるが、０．１％を超えると靱性に悪影響を及ぼすことから、０．１質量％以下とすることが好ましい。なお、Ｔｉはオーステナイトを微細化し、その結果、微細なラス状のマルテンサイト組織を形成する効果を有すると考えられる。 Ti: 0.1% by mass or less Ti is an element useful for ensuring the strength and toughness of the base material and the HAZ part, but if it exceeds 0.1%, it adversely affects the toughness, so 0.1 It is preferably mass% or less. It is considered that Ti has the effect of refining austenite and, as a result, forming a fine lath-like martensite structure.
　Ｂ：０．００４０質量％以下
　Ｂは、圧延中にオーステナイト粒界に偏析して焼入性を上げる作用があるが、０．００４０質量％を超えるとＨＡＺ部の靱性を劣化させることから、０．００４０質量％以下とすることが好ましい。 B: 0.0040% by mass or less B has the effect of segregating at the austenite grain boundary during rolling to improve the hardenability, but if it exceeds 0.0040% by mass, the toughness of the HAZ portion deteriorates, so it is 0. It is preferably 0040% by mass or less.
　その他、不純物としてはＮがあり、多量に含有されると窒化物を形成して靱性の低下を 招くので、Ｎの混入量は０．０１０質量％以下とすることが好ましい。 In addition, there is N as an impurity, and if it is contained in a large amount, a nitride is formed and the toughness is lowered. Therefore, the amount of N mixed is preferably 0.010% by mass or less.
（２）固相接合継手
　本発明の固相接合継手に関して、摩擦攪拌接合によって形成された固相接合部を有する場合の一態様を図１に、摩擦圧接によって形成された固相接合部を有する場合の一態様を図２に、線形摩擦接合によって形成された固相接合部を有する場合の一態様を図３に、それぞれ示す。摩擦圧接又は線形摩擦接合を用いた場合は被接合材（２，４）の摩擦面に固相接合部６が形成され、摩擦攪拌接合を用いた場合は摩擦攪拌接合用ツールが通過した領域に固相接合部６が形成される。 (2) Solid-State Joint Joint The solid-phase joint of the present invention has a solid-phase joint formed by friction welding, as shown in FIG. One aspect of the case is shown in FIG. 2, and one aspect of the case having a solid-state joint formed by linear friction welding is shown in FIG. When friction welding or linear friction welding is used, a solid phase bonding portion 6 is formed on the friction surface of the material to be bonded (2, 4), and when friction stir welding is used, the area through which the friction stir welding tool has passed. The solid phase junction 6 is formed.
　摩擦攪拌接合に関しては、（１）金属板の端部同士を突き合わせて接合部とし、回転ツールをその加工部の長手方向に沿って回転させつつ移動させて金属板同士を接合する接合、（２）金属板の端部同士を突き合わせて接合部とし、回転ツールをその接合部で移動させずに回転させて接合するスポット接合、（３）金属板同士を接合部において重ね合わせ、接合部に回転ツールを挿入し、回転ツールをその箇所で移動させずに回転させて金属板同士を接合するスポット接合、（４）金属板同士を接合部において重ね合わせ、接合部に回転ツールを挿入し、回転ツールをその接合部の長手方向に沿って回転させつつ移動させて金属板同士を接合する接合の（１）～（４）の４つの態様及びこれらの組み合わせが含まれる。 Regarding friction-stirring joining, (1) the ends of the metal plates are butted against each other to form a joining portion, and the rotating tool is moved while rotating along the longitudinal direction of the processed portion to join the metal plates to each other, (2). ) Spot joining where the ends of metal plates are butted against each other to form a joint, and the rotation tool is rotated and joined without moving at the joint. (3) Metal plates are overlapped at the joint and rotated to the joint. Insert the tool and rotate the rotation tool without moving it at that point to join the metal plates in a spot joint. (4) Overlay the metal plates at the joint, insert the rotation tool in the joint, and rotate. Included are four embodiments (1)-(4) of joining the metal plates by moving the tool while rotating it along the longitudinal direction of the joining portion, and a combination thereof.
　本発明の固相接合継手１では、被接合材（２，４）のうちの少なくとも一方が、本発明の固相接合用鋼からなる固相接合用鋼材となっている。また、固相接合部６の組織はラス状のマルテンサイト組織を有している。ここで、固相接合部６の殆どの領域をラス状のマルテンサイト組織とすることで、極めて高い強度を得ることができる。一方で、一般的なマルテンサイト組織では十分な延性を発現することが困難であるが、本願発明者がマルテンサイト組織と引張特性の関係を鋭意調査した結果、Ｍｎの添加によりラス状のマルテンサイト組織を微細化することで、良好な延性を付与できることが明らかになった。 In the solid-phase joint 1 of the present invention, at least one of the materials to be joined (2, 4) is a steel material for solid-phase bonding made of the steel for solid-phase bonding of the present invention. Further, the structure of the solid phase junction 6 has a lath-shaped martensite structure. Here, by forming most of the region of the solid phase bonding portion 6 into a lath-shaped martensite structure, extremely high strength can be obtained. On the other hand, it is difficult to develop sufficient ductility with a general martensite structure, but as a result of diligent investigation of the relationship between the martensite structure and the tensile properties by the inventor of the present application, lath-shaped martensite due to the addition of Mn. It was clarified that good ductility can be imparted by making the tissue finer.
　固相接合部６では、マルテンサイト組織における旧オーステナイトの平均粒径が１５μｍ以下となっている。旧オーステナイト組織を微細化することで、ラス状のマルテンサイト組織が微細化され、固相接合部に高い強度と延性を付与することができる。ここで、旧オーステナイトの平均粒径は１０μｍ以下であることがより好ましく、５μｍ以下であることが最も好ましい。なお、旧オーステナイトの平均粒径を求める方法は特に限定されず従来公知の種々の方法を用いることができるが、例えば、適当なエッチングを施した組織を観察してもよく、マルテンサイトと旧オーステナイトとの方位関係により、マルテンサイトから旧オーステナイトを再構築し、再構築した旧オーステナイト組織から求めてもよい。 In the solid phase junction 6, the average particle size of the former austenite in the martensite structure is 15 μm or less. By refining the old austenite structure, the lath-shaped martensite structure is miniaturized, and high strength and ductility can be imparted to the solid-phase junction. Here, the average particle size of the old austenite is more preferably 10 μm or less, and most preferably 5 μm or less. The method for determining the average particle size of the former austenite is not particularly limited, and various conventionally known methods can be used. For example, a structure subjected to appropriate etching may be observed, and martensite and the former austenite may be observed. Depending on the orientation relationship with, the former austenite may be reconstructed from martensite and obtained from the reconstructed former austenite organization.
　また、被接合材（２，４）のビッカース硬度が４００ＨＶ以上、固相接合部６のビッカース硬度が４００ＨＶ以上、固相接合部６近傍の熱影響部のビッカース硬度が４００ＨＶ以上、であることが好ましい。より好ましいビッカース硬度は、被接合材（２，４）、固相接合部６及び熱影響部共に４５０ＨＶ以上である。 Further, the Vickers hardness of the material to be joined (2, 4) is 400 HV or more, the Vickers hardness of the solid phase joint 6 is 400 HV or more, and the Vickers hardness of the heat-affected zone near the solid phase joint 6 is 400 HV or more. preferable. A more preferable Vickers hardness is 450 HV or more for the material to be bonded (2, 4), the solid phase bonded portion 6, and the heat-affected zone.
　また、固相接合部６及び熱影響部のビッカース硬度が、被接合材（２，４）のビッカース硬度の８０～１２０％の値となることが好ましい。被接合材（２，４）、固相接合部６及び熱影響部の強化機構は同一ではないが、最終的にこれらの硬度のばらつきを低減することで、機械的性質に特異領域のない良好な継手とすることができる。 Further, it is preferable that the Vickers hardness of the solid phase bonding portion 6 and the heat-affected zone is a value of 80 to 120% of the Vickers hardness of the material to be bonded (2, 4). The strengthening mechanisms of the material to be joined (2, 4), the solid-phase joint 6 and the heat-affected zone are not the same, but by finally reducing the variation in hardness, the mechanical properties are good with no peculiar region. Can be a good joint.
　また、熱影響部にＶ、Ｗ及びＭｏのうちの少なくとも１種を含む二次炭化物を有することが好ましい。固相接合継手１全体の硬度分布を均質化するためには熱影響部の硬度低下を抑制する必要があるが、当該領域に高硬度の二次炭化物を分散させることにより、極めて効果的に軟化を抑制することができる。 Further, it is preferable to have a secondary carbide containing at least one of V, W and Mo in the heat-affected zone. In order to homogenize the hardness distribution of the entire solid-phase joint joint 1, it is necessary to suppress the decrease in hardness of the heat-affected zone, but by dispersing high-hardness secondary carbides in the region, it is extremely effectively softened. Can be suppressed.
　また、固相接合継手１は、室温での引張強さが１０００ＭＰａ以上、伸びが２０％以上であることが好ましく、１２００ＭＰａ以上、伸びが２０％以上であることがより好ましく、１５００ＭＰａ以上、伸びが２０％以上であることが最も好ましい。被接合材（２，４）と固相接合部６に高い引張特性を付与すると共に、熱影響部での軟化を抑制することで、これらの値を実現することができる。固相接合継手１がこれらの引張特性を有することで、高い強度と信頼性が要求される用途において、超高張力鋼と同等以上の機械的性質を有する継手として十分に使用することができる。ここで、引張試験の結果は引張試験片のサイズ及び形状の影響を受ける場合が存在するが、本願明細書においては、平行部の長さが４ｍｍ、幅が２ｍｍ程度の、比較的小型の引張試験片を用いて得られた値を基準とする。 Further, the solid phase joint 1 preferably has a tensile strength of 1000 MPa or more and an elongation of 20% or more at room temperature, more preferably 1200 MPa or more and an elongation of 20% or more, and an elongation of 1500 MPa or more. Most preferably, it is 20% or more. These values can be realized by imparting high tensile properties to the material to be bonded (2, 4) and the solid-phase bonded portion 6 and suppressing softening in the heat-affected zone. Since the solid-phase joint 1 has these tensile properties, it can be sufficiently used as a joint having mechanical properties equal to or higher than those of ultra-high-strength steel in applications requiring high strength and reliability. Here, the result of the tensile test may be affected by the size and shape of the tensile test piece, but in the present specification, a relatively small tensile strength having a parallel portion having a length of 4 mm and a width of about 2 mm. The value obtained using the test piece is used as a reference.
　固相接合継手１の固相接合部６は摩擦圧接や線形摩擦接合によって形成されたものでもよいが、摩擦攪拌接合部とすることで、鋼板の任意の領域に固相接合部６を形成することができ、大型構造物の製造にも対応が可能である。 The solid-state joint 6 of the solid-phase joint 1 may be formed by friction welding or linear friction welding, but by forming the friction stir joint, the solid-state joint 6 is formed in an arbitrary region of the steel plate. It is possible to handle the production of large structures.
（３）固相接合構造物
　本発明の固相接合構造物は、固相接合継手１を有することを特徴としている。固相接合継手１以外の構造部に関する材質、形状及びサイズは特に限定されず、従来公知の種々の構造物とすることができる。 (3) Solid-Phase Bonding Structure The solid-phase bonding structure of the present invention is characterized by having a solid-phase bonding joint 1. The material, shape, and size of the structural parts other than the solid-phase joint 1 are not particularly limited, and various conventionally known structures can be used.
　本発明の効果を損なわない限りにおいて、固相接合構造物は特に限定されないが、例えば、自動車、船舶及び鉄道車両等の輸送用機器の構造部、各種建築構造物、橋梁、鉄管等を挙げることができる。 The solid-phase bonded structure is not particularly limited as long as the effect of the present invention is not impaired, and examples thereof include structural parts of transportation equipment such as automobiles, ships and railroad vehicles, various building structures, bridges and iron pipes. Can be done.
（４）固相接合用鋼材
　本発明の固相接合用鋼材は、本発明の固相接合用鋼からなり、ラス状のマルテンサイト組織を有し、当該マルテンサイト組織における旧オーステナイトの平均粒径が１５μｍ以下であること、を特徴とする固相接合用鋼材である。当該組成及び組織を有する固相接合用鋼材は、室温での引張強さが１０００ＭＰａ以上、伸びが２０％以上となり、高い強度と信頼性が要求される用途において、超高張力鋼と同等以上の機械的性質を有する鋼材として十分に使用することができる (4) Steel material for solid phase bonding The steel material for solid phase bonding of the present invention is composed of the steel for solid phase bonding of the present invention, has a lath-shaped martensite structure, and has an average particle size of former austenite in the martensite structure. It is a steel material for solid phase bonding, characterized in that the thickness is 15 μm or less. The solid-phase bonding steel material having the composition and structure has a tensile strength of 1000 MPa or more and an elongation of 20% or more at room temperature, which is equal to or higher than that of ultra-high-strength steel in applications requiring high strength and reliability. Can be sufficiently used as a steel material having mechanical properties
　以上、本発明の代表的な実施形態について説明したが、本発明はこれらのみに限定されるものではなく、種々の設計変更が可能であり、それら設計変更は全て本発明の技術的範囲に含まれる。 Although the typical embodiments of the present invention have been described above, the present invention is not limited to these, and various design changes are possible, and all of these design changes are included in the technical scope of the present invention. Is done.
　以下、実施例において本発明の固相接合用鋼、固相接合用鋼材、固相接合継手及び固相接合構造物について更に説明するが、本発明はこれらの実施例に何ら限定されるものではない。 Hereinafter, the steel for solid phase bonding, the steel material for solid phase bonding, the solid phase joint, and the solid phase bonding structure of the present invention will be further described in Examples, but the present invention is not limited to these Examples. No.
≪実施例１≫
　高周波溶解により表１に示す組成を有する鋼のインゴット（φ３５×２０～２５ｈ）を作製し、１０００℃の熱間圧延にて板厚を３ｍｍに調整した。その後、Ｍｏを完全にオーステナイト中に固溶させると共にマルテンサイト組織を得るために、１０００℃で１０分間の均熱拡散処理を施した後に水冷して鋼板（実施固相接合用鋼１）を得た。なお、表１に示す値は質量％である。 << Example 1 >>
A steel ingot (φ35 × 20 to 25 h) having the composition shown in Table 1 was prepared by high-frequency melting, and the plate thickness was adjusted to 3 mm by hot rolling at 1000 ° C. Then, in order to completely dissolve Mo in austenite and obtain a martensite structure, a steel sheet (Steel 1 for solid phase bonding) was obtained by subjecting Mo to a soaking heat diffusion treatment at 1000 ° C. for 10 minutes and then cooling with water. rice field. The values shown in Table 1 are mass%.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　得られた鋼板に対し、ショルダ径１５ｍｍ、プローブ径６ｍｍ、プローブ長２．９ｍｍの形状を有する超硬合金製ツール（プローブにネジを有していない）を用い、ツール回転速度：４００ｒｐｍ、接合速度：１５０ｍｍ／ｍｉｎ、接合荷重：２．５ｔｏｎ、ツール前進角：３°、接合雰囲気：Ａｒの条件で摩擦攪拌接合を行った。 A cemented carbide tool (the probe does not have a screw) having a shape of a shoulder diameter of 15 mm, a probe diameter of 6 mm, and a probe length of 2.9 mm was used for the obtained steel plate, and the tool rotation speed: 400 rpm, joining speed. Friction stir welding was performed under the conditions of: 150 mm / min, joining load: 2.5 ton, tool advance angle: 3 °, and joining atmosphere: Ar.
≪実施例２≫
　表１に示す実施例２の組成を用いた以外は実施例１と同様にして、鋼板（実施固相接合用鋼２）を得た。また、実施例１と同様にして、摩擦攪拌接合を施した。 << Example 2 >>
A steel sheet (Steel 2 for solid phase bonding) was obtained in the same manner as in Example 1 except that the composition of Example 2 shown in Table 1 was used. Further, friction stir welding was performed in the same manner as in Example 1.
≪実施例３≫
　表１に示す実施例３の組成を用いた以外は実施例１と同様にして、鋼板（実施固相接合用鋼３）を得た。また、実施例１と同様にして、摩擦攪拌接合を施した。 << Example 3 >>
A steel sheet (Steel 3 for solid phase bonding) was obtained in the same manner as in Example 1 except that the composition of Example 3 shown in Table 1 was used. Further, friction stir welding was performed in the same manner as in Example 1.
≪実施例４≫
　表１に示す実施例４の組成を用い、均熱拡散処理の温度を１１２５℃としたこと以外は実施例１と同様にして、鋼板（実施固相接合用鋼４）を得た。また、実施例１と同様にして、摩擦攪拌接合を施した。 << Example 4 >>
Using the composition of Example 4 shown in Table 1, a steel sheet (Steel 4 for solid phase bonding) was obtained in the same manner as in Example 1 except that the temperature of the soaking heat diffusion treatment was set to 1125 ° C. Further, friction stir welding was performed in the same manner as in Example 1.
≪比較例１≫
　表１に示す比較例１の組成を用いた以外は実施例１と同様にして、鋼板（比較固相接合用鋼１）を得た。また、実施例１と同様にして、摩擦攪拌接合を施した。 << Comparative Example 1 >>
A steel sheet (Steel 1 for comparative solid phase bonding) was obtained in the same manner as in Example 1 except that the composition of Comparative Example 1 shown in Table 1 was used. Further, friction stir welding was performed in the same manner as in Example 1.
≪比較例２≫
　表１に示す比較例２の組成を用いた以外は実施例１と同様にして、鋼板（比較固相接合用鋼２）を得た。また、実施例１と同様にして、摩擦攪拌接合を施した。 << Comparative Example 2 >>
A steel sheet (Steel 2 for comparative solid phase bonding) was obtained in the same manner as in Example 1 except that the composition of Comparative Example 2 shown in Table 1 was used. Further, friction stir welding was performed in the same manner as in Example 1.
≪比較例３≫
　表１に示す比較例３の組成を用いた以外は実施例１と同様にして、鋼板（比較固相接合用鋼３）を得た。また、実施例１と同様にして、摩擦攪拌接合を施した。 << Comparative Example 3 >>
A steel sheet (Steel 3 for comparative solid phase bonding) was obtained in the same manner as in Example 1 except that the composition of Comparative Example 3 shown in Table 1 was used. Further, friction stir welding was performed in the same manner as in Example 1.
［評価試験］
（１）組織観察
　摩擦攪拌接合方向に対して垂直に攪拌部を含む領域を切り出し、断面を研磨及び腐食（４％ナイタール）した後、走査電子顕微鏡（ＦＥ－ＳＥＭ，日本電子株式会社製ＪＳＭ－７００１ＦＡ）を用いて組織観察を行った。なお、研磨にはエメリー紙（＃６００～＃３０００）及びダイヤモンドペースト（粒度３μｍ及び１μｍ）を用いた。また、母材観察用の試料も同様に準備した。 [Evaluation test]
(1) Structure observation After cutting out the area including the stirring part perpendicular to the friction stir welding direction, polishing and corroding the cross section (4% nital), scanning electron microscope (FE-SEM, JSM-manufactured by JEOL Ltd.) Tissue observation was performed using 7001FA). Emery paper (# 600 to # 3000) and diamond paste (particle size 3 μm and 1 μm) were used for polishing. A sample for observing the base metal was also prepared in the same manner.
（２）ＥＢＳＤ測定
　母材及び摩擦攪拌接合継手の攪拌部における旧オーステナイト粒径を測定するため、ＥＢＳＤ測定を行った。ＥＢＳＤ測定にはＦＥ－ＳＥＭ（日本電子株式会社製ＪＳＭ－７００１ＦＡ）及びＴＳＬ社製のＯＩＭ　ｄａｔａ　Ｃｏｌｌｅｃｔｉｏｎ　ｖｅｒ５．３１を用いた。 (2) EBSD measurement In order to measure the particle size of the old austenite in the stirring part of the base metal and the friction stir welding joint, EBSD measurement was performed. For EBSD measurement, FE-SEM (JSM-7001FA manufactured by JEOL Ltd.) and OIM data Collection ver5.31 manufactured by TSL were used.
（３）ビッカース硬度測定
　上記実施例及び比較例で得られた摩擦攪拌接合継手の接合部横断面に対してビッカース硬度測定を行った。測定部は板厚中心とし、水平方向の硬度分布を測定した。測定装置にはＦＵＴＵＲＥ－ＴＥＣＨ製のＡＲＳ　１０Ｋを用い、１ｋｇ、１０ｓの条件で測定を行った。 (3) Vickers hardness measurement Vickers hardness was measured on the cross section of the joint portion of the friction stir welding joints obtained in the above Examples and Comparative Examples. The measuring part was centered on the plate thickness, and the hardness distribution in the horizontal direction was measured. ARS 10K manufactured by FUTURE-TECH was used as a measuring device, and measurement was performed under the conditions of 1 kg and 10 s.
　実施固相接合用鋼２、実施固相接合用鋼３及び比較固相接合用鋼１の母材及び攪拌部の組織観察結果（ＳＥＭ観察像）を図４に示す。実施固相接合用鋼２、実施固相接合用鋼３及び比較固相接合用鋼１の全てにおいて、母材ではオーステナイト域からの水冷によりフルマルテンサイト組織が形成されている。また、攪拌部においても、接合温度がＡ３点以上となる摩擦攪拌接合により、母材と同様のフルマルテンサイト組織となっている。母材及び攪拌部の両方で微細な球状粒子が観察されるが、これはマトリックス中に固溶されなかったＶ炭化物であると考えられる。 FIG. 4 shows the structure observation results (SEM observation image) of the base material and the stirring portion of the implemented solid phase bonding steel 2, the implemented solid phase bonding steel 3, and the comparative solid phase bonding steel 1. In all of the implementation solid-phase bonding steel 2, the implementation solid-phase bonding steel 3, and the comparative solid-phase bonding steel 1, a fulmartensite structure is formed in the base metal by water cooling from the austenite region. Further, even in the stirring unit, by friction stir welding bonding temperature is equal to or higher than 3 points A, has the same full martensite and the base metal. Fine spherical particles are observed in both the base metal and the stirring part, which are considered to be V carbides that were not dissolved in the matrix.
　実施固相接合用鋼３の母材、攪拌部及び熱影響部の組織観察結果を図５に並べて示す。母材と比較すると熱影響部の組織はやや粗大化していることが分かる。一方で、マトリックス中に固溶されなかったＶ炭化物には大きな変化が認められない。なお、後述のビッカース硬度測定の結果からは、Ｖの添加によって熱影響部の軟化が効果的に抑制されていることから、ＳＥＭ観察では明瞭に観察できない微細なＶの二次炭化物が形成されていると考えられる。 Fig. 5 shows the microstructure observation results of the base material, stirring part, and heat-affected zone of the steel for solid phase bonding. It can be seen that the structure of the heat-affected zone is slightly coarser than that of the base material. On the other hand, no significant change is observed in the V carbide that was not dissolved in the matrix. From the results of the Vickers hardness measurement described later, since the softening of the heat-affected zone is effectively suppressed by the addition of V, fine V secondary carbides that cannot be clearly observed by SEM observation are formed. It is thought that there is.
　実施固相接合用鋼２、実施固相接合用鋼３及び比較固相接合用鋼１に関して、ＥＢＳＤ測定結果から、マルテンサイトと旧オーステナイトとの方位関係により、母材及び攪拌部のマルテンサイトから旧オーステナイトを再構築した結果を図６に示す。Ｖの添加によって旧オーステナイト粒が微細化していることが分かる。特に、攪拌部において、１．０％のＶを添加した場合は約４μｍの極めて微細な旧オーステナイト粒径となっている。 Regarding the steel for solid phase bonding 2, the steel 3 for solid phase bonding and the steel 1 for comparative solid phase bonding, from the EBSD measurement results, from the martensite of the base material and the stirring part according to the orientation relationship between martensite and the former austenite. The result of reconstructing the old austenite is shown in FIG. It can be seen that the addition of V makes the old austenite grains finer. In particular, when 1.0% V is added to the stirring portion, the particle size of the old austenite is extremely fine, about 4 μm.
　実施固相接合用鋼１、比較固相接合用鋼１、比較固相接合用鋼２及び比較固相接合用鋼３の摩擦攪拌接合継手の接合部横断面におけるビッカース硬度分布を図７に示す。図７には、ビッカース硬度測定位置に対応した接合部横断面の模式図も示している。比較固相接合用鋼１、比較固相接合用鋼２及び比較固相接合用鋼３においては、熱影響部で顕著な軟化が認められる。これに対し、３．０％のＭｏを添加した実施固相接合用鋼１では、当該軟化が効果的に抑制されており、最低硬度が４５０ＨＶ以上となっている。加えて、攪拌部及び熱影響部のビッカース硬度は、母材のビッカース硬度の８０～１２０％の値となっている。 FIG. 7 shows the Vickers hardness distribution in the cross section of the joint portion of the friction stir welding joint of the steel 1 for solid phase welding, the steel 1 for comparative solid phase welding, the steel 2 for comparative solid phase welding, and the steel 3 for comparative solid phase welding. .. FIG. 7 also shows a schematic view of the cross section of the joint corresponding to the Vickers hardness measurement position. In the comparative solid phase bonding steel 1, the comparative solid phase bonding steel 2, and the comparative solid phase bonding steel 3, remarkable softening is observed in the heat-affected zone. On the other hand, in the steel 1 for solid phase bonding to which 3.0% Mo was added, the softening was effectively suppressed, and the minimum hardness was 450 HV or more. In addition, the Vickers hardness of the stirring part and the heat-affected zone is a value of 80 to 120% of the Vickers hardness of the base material.
　実施固相接合用鋼２、実施固相接合用鋼３、実施固相接合用鋼４及び比較固相接合用鋼１の摩擦攪拌接合継手の接合部横断面におけるビッカース硬度分布を図８に示す。図８には、ビッカース硬度測定位置に対応した接合部横断面の模式図も示している。比較固相接合用鋼１においては、熱影響部で顕著な軟化が認められる。これに対し、０．５％及び１．０％のＭｏを添加した実施固相接合用鋼では、当該軟化が効果的に抑制されており、最低硬度は何れの場合も４００ＨＶ以上となっている。加えて、攪拌部及び熱影響部のビッカース硬度は、母材のビッカース硬度の８０～１２０％の値となっている。ここで、Ｖの場合は０．５％添加と１．０％添加の場合で大差はなく、比較的少量の添加で熱影響部の軟化が抑制されることが分かる。また、均熱拡散処理の温度が最低硬度に及ぼす影響も顕著には認められない。一方で、Ｍｏを３．０％添加した場合と比較すると、最低硬度はやや低い値となっている。 FIG. 8 shows the Vickers hardness distribution in the cross section of the joint portion of the friction stir welding steel 2, the steel for implementing solid phase welding 2, the steel for implementing solid phase bonding 3, the steel for implementing solid phase bonding 4, and the steel for comparative solid phase welding 1. .. FIG. 8 also shows a schematic view of the cross section of the joint corresponding to the Vickers hardness measurement position. In the comparative solid phase bonding steel 1, remarkable softening is observed in the heat-affected zone. On the other hand, in the solid phase bonding steels to which 0.5% and 1.0% Mo were added, the softening was effectively suppressed, and the minimum hardness was 400 HV or more in each case. .. In addition, the Vickers hardness of the stirring part and the heat-affected zone is a value of 80 to 120% of the Vickers hardness of the base material. Here, in the case of V, there is no big difference between the case of adding 0.5% and the case of adding 1.0%, and it can be seen that the softening of the heat-affected zone is suppressed by adding a relatively small amount. In addition, the effect of the temperature of the soaking heat diffusion treatment on the minimum hardness is not significantly observed. On the other hand, the minimum hardness is slightly lower than that when 3.0% of Mo is added.
１・・・固相接合継手、
２，４・・・被接合材、
６・・・固相接合部。 1 ... Solid phase joint,
2,4 ... Material to be joined,
6 ... Solid phase joint.

Claims (9)

  1. 　鋼組成が、質量％で、
    　Ｃ：０．２０～２．１４％、
    　ＳｉとＡｌの合計：１．００～３．００％、
    　Ｍｎ：２．００～５．００％、を含有すると共に、
    　Ｖ：０．１％超３．０％以下、Ｗ：１．０％超６．０％以下、Ｍｏ：１．０％超６．０％以下、のうちの少なくとも１種を含有し、
    　残部がＦｅ及び不可避不純物のみの組成であること、
    　を特徴とする固相接合用鋼。     Steel composition by mass%
    C: 0.20 to 2.14%,
    Total of Si and Al: 1.00 to 3.00%,
    Mn: 2.00 to 5.00%, and
    It contains at least one of V: more than 0.1% and 3.0% or less, W: more than 1.0% and 6.0% or less, and Mo: more than 1.0% and 6.0% or less.
    The balance is composed of Fe and unavoidable impurities only.
    Steel for solid phase bonding.
  2. 　前記Ｃの含有量が０．２０～０．４５質量％であること、
    　を特徴とする請求項１に記載の固相接合用鋼。     The content of C is 0.20 to 0.45% by mass.
    The steel for solid phase bonding according to claim 1.
  3. 　被接合材の少なくとも一方が請求項１又は２に記載の固相接合用鋼からなる固相接合用鋼材であり、
    　前記固相接合用鋼材の固相接合部がラス状のマルテンサイト組織を有し、
    　前記マルテンサイト組織における旧オーステナイトの平均粒径が１５μｍ以下であること、
    　を特徴とする固相接合継手。     At least one of the materials to be joined is a steel material for solid-phase bonding, which is the steel for solid-phase bonding according to claim 1 or 2.
    The solid phase joint portion of the solid phase bonding steel material has a lath-shaped martensite structure.
    The average particle size of the old austenite in the martensite structure is 15 μm or less.
    A solid-phase joint that features.
  4. 　前記固相接合用鋼材のビッカース硬度が４００ＨＶ以上、
    　前記固相接合部のビッカース硬度が４００ＨＶ以上、
    　前記固相接合部近傍の熱影響部のビッカース硬度が４００ＨＶ以上、であること、
    　を特徴とする請求項３に記載の固相接合継手。     The Vickers hardness of the solid phase bonding steel material is 400 HV or more,
    The Vickers hardness of the solid phase junction is 400 HV or more,
    The Vickers hardness of the heat-affected zone near the solid-phase junction is 400 HV or more.
    The solid phase joint according to claim 3.
  5. 　前記固相接合部及び前記熱影響部のビッカース硬度が、前記固相接合用鋼材のビッカース硬度の８０～１２０％の値となること、
    を特徴とする請求項３又は４に記載の固相接合継手。     The Vickers hardness of the solid-phase bonding portion and the heat-affected zone shall be a value of 80 to 120% of the Vickers hardness of the solid-phase bonding steel material.
    The solid phase joint according to claim 3 or 4.
  6. 　前記熱影響部にＶ、Ｗ及びＭｏのうちの少なくとも１種を含む二次炭化物を有すること、
    を特徴とする請求項３～５のうちのいずれかに記載の固相接合継手。     Having a secondary carbide containing at least one of V, W and Mo in the heat-affected zone.
    The solid phase joint according to any one of claims 3 to 5.
  7. 前記固相接合部が摩擦攪拌接合部であること、
    を特徴とする請求項３～６のうちのいずれかに記載の固相接合継手。     That the solid phase joint is a friction stir weld
    The solid phase joint according to any one of claims 3 to 6.
  8. 請求項３～７のうちのいずれかに記載の固相接合継手を有すること、
    を特徴とする固相接合構造物。     Having the solid phase joint according to any one of claims 3 to 7.
    A solid phase bonding structure characterized by.
  9. 請求項１又は２に記載の固相接合用鋼からなり、
    ラス状のマルテンサイト組織を有し、
    前記マルテンサイト組織における旧オーステナイトの平均粒径が１５μｍ以下であること、
    を特徴とする固相接合用鋼材。     The steel for solid phase bonding according to claim 1 or 2.
    It has a lath-like martensite structure and has a lath-like martensite structure.
    The average particle size of the old austenite in the martensite structure is 15 μm or less.
    A steel material for solid phase bonding.
PCT/JP2021/010577 2020-03-18 2021-03-16 Steel for solid-state welding, steel material for solid-state welding, solid-state welded joint, and solid-state welded structure WO2021187473A1 (en)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH03199307A (en) * 1989-12-28 1991-08-30 Kawasaki Steel Corp Production of steel products having excellent friction pressure weldability
JP2009161165A (en) * 2007-12-05 2009-07-23 Honda Motor Co Ltd Strength member for vehicle
JP2012509178A (en) * 2008-11-18 2012-04-19 エクソンモービル リサーチ アンド エンジニアリング カンパニー High strength and high toughness steel structure by friction stir welding
JP2014162971A (en) * 2013-02-27 2014-09-08 Jfe Bars & Shapes Corp Steel for friction stirring process and high strength steel member
WO2020184123A1 (en) * 2019-03-12 2020-09-17 国立大学法人大阪大学 Steel for solid-state welding, steel material for solid-state welding, solid-state welded joint, and solid-state welded structure
WO2020184124A1 (en) * 2019-03-12 2020-09-17 国立大学法人大阪大学 Weathering steel for solid-state welding, weathering steel material for solid state welding, solid-state welded structure and solid-state welding method

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH03199307A (en) * 1989-12-28 1991-08-30 Kawasaki Steel Corp Production of steel products having excellent friction pressure weldability
JP2009161165A (en) * 2007-12-05 2009-07-23 Honda Motor Co Ltd Strength member for vehicle
JP2012509178A (en) * 2008-11-18 2012-04-19 エクソンモービル リサーチ アンド エンジニアリング カンパニー High strength and high toughness steel structure by friction stir welding
JP2014162971A (en) * 2013-02-27 2014-09-08 Jfe Bars & Shapes Corp Steel for friction stirring process and high strength steel member
WO2020184123A1 (en) * 2019-03-12 2020-09-17 国立大学法人大阪大学 Steel for solid-state welding, steel material for solid-state welding, solid-state welded joint, and solid-state welded structure
WO2020184124A1 (en) * 2019-03-12 2020-09-17 国立大学法人大阪大学 Weathering steel for solid-state welding, weathering steel material for solid state welding, solid-state welded structure and solid-state welding method

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