JP7492116B2 - Steel plates for friction welding, composite materials and automotive materials - Google Patents
Steel plates for friction welding, composite materials and automotive materials Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims description 157
- 239000010959 steel Substances 0.000 title claims description 157
- 238000003466 welding Methods 0.000 title claims description 92
- 239000000463 material Substances 0.000 title claims description 30
- 239000002131 composite material Substances 0.000 title claims description 11
- 229910000734 martensite Inorganic materials 0.000 claims description 48
- 229910001563 bainite Inorganic materials 0.000 claims description 47
- 238000007747 plating Methods 0.000 claims description 27
- 229910052782 aluminium Inorganic materials 0.000 claims description 10
- 239000012535 impurity Substances 0.000 claims description 10
- 239000000203 mixture Substances 0.000 claims description 10
- 229910052742 iron Inorganic materials 0.000 claims description 8
- 229910052725 zinc Inorganic materials 0.000 claims description 7
- 238000000034 method Methods 0.000 description 23
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 21
- 238000005304 joining Methods 0.000 description 20
- 238000004519 manufacturing process Methods 0.000 description 17
- 230000007423 decrease Effects 0.000 description 14
- 229910052761 rare earth metal Inorganic materials 0.000 description 13
- 150000002910 rare earth metals Chemical class 0.000 description 13
- 229910000859 α-Fe Inorganic materials 0.000 description 11
- 238000001878 scanning electron micrograph Methods 0.000 description 10
- 230000000694 effects Effects 0.000 description 9
- 239000011651 chromium Substances 0.000 description 8
- 239000010949 copper Substances 0.000 description 8
- 238000010438 heat treatment Methods 0.000 description 8
- 229910052751 metal Inorganic materials 0.000 description 8
- 239000002184 metal Substances 0.000 description 8
- 239000011701 zinc Substances 0.000 description 7
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 6
- 238000005246 galvanizing Methods 0.000 description 5
- 229910052710 silicon Inorganic materials 0.000 description 5
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 4
- FJMNNXLGOUYVHO-UHFFFAOYSA-N aluminum zinc Chemical compound [Al].[Zn] FJMNNXLGOUYVHO-UHFFFAOYSA-N 0.000 description 4
- 229910001566 austenite Inorganic materials 0.000 description 4
- 229910001567 cementite Inorganic materials 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 238000001556 precipitation Methods 0.000 description 4
- 239000010703 silicon Substances 0.000 description 4
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 3
- 238000000137 annealing Methods 0.000 description 3
- 150000001247 metal acetylides Chemical class 0.000 description 3
- 229910001562 pearlite Inorganic materials 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 230000000717 retained effect Effects 0.000 description 3
- 238000005096 rolling process Methods 0.000 description 3
- 238000009864 tensile test Methods 0.000 description 3
- 229910052726 zirconium Inorganic materials 0.000 description 3
- 229910000838 Al alloy Inorganic materials 0.000 description 2
- 229910001122 Mischmetal Inorganic materials 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 238000005097 cold rolling Methods 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000005530 etching Methods 0.000 description 2
- -1 iron carbides Chemical class 0.000 description 2
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 2
- 239000007769 metal material Substances 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 230000000149 penetrating effect Effects 0.000 description 2
- 238000005554 pickling Methods 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000005496 tempering Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 229910000851 Alloy steel Inorganic materials 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910001335 Galvanized steel Inorganic materials 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- 239000004566 building material Substances 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 239000010960 cold rolled steel Substances 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000009713 electroplating Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 239000008397 galvanized steel Substances 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 150000002484 inorganic compounds Chemical class 0.000 description 1
- 229910010272 inorganic material Inorganic materials 0.000 description 1
- 229910052747 lanthanoid Inorganic materials 0.000 description 1
- 150000002602 lanthanoids Chemical class 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 229910052706 scandium Inorganic materials 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 150000003568 thioethers Chemical class 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
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- Pressure Welding/Diffusion-Bonding (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Description
本開示は、摩擦圧接用鋼板、複合部材および自動車用部材に関する。 This disclosure relates to steel plates for friction welding, composite components, and automotive components.
複数枚の金属板を接合する手段として、重ね合わされた複数枚の金属板を、リベットなどの接続部材を用いて接合する技術が知られている。
特に近年では、重ね合わされた上板と下板に対して、接続部材を回転させながら上板の上面に押圧し、上板を貫通させて、接続部材と下板とを摩擦圧接する接合技術などが検討されている。
As a means for joining a plurality of metal plates, a technique is known in which a plurality of overlapping metal plates are joined by using connecting members such as rivets.
In particular, in recent years, joining techniques have been considered in which a connecting member is rotated and pressed against the upper surface of the upper plate while penetrating the upper plate, thereby frictionally welding the connecting member and the lower plate.
例えば、特許文献１には、アルミニウム板と鋼板のような強度の異なる２枚の板材を、リベット等の接合要素（すなわち、頭部及び軸部を有する接続部材）を用いて、摩擦圧接のプロセスにより接合する技術が開示されている。具体的には、次のようなプロセスを経て、強度の異なる２枚の板材を接合する技術が開示されている。
すなわち、２枚の板材を、強度の低い方の板材を上板にして重ね合わせ、上板の上面に、ホルダに支持された接続部材をセットし、接続部材を回転させながら下方に移動させて、上板の内部に向けて押圧する。このとき、接続部材と上板との聞には、接続部材の回転によって強い摩擦が生じ、接続部材の先端部が加熱されるため、上板が軟化して、接続部材が上板内に進入することが可能となる。
このようにして、回転しながら上板内に進入する接続部材の先端部が、下板の上面に到達すると、接続部材の軸部と下板との間で摩擦圧接のプロセスが進行し、接続部材の軸部と下板が摩擦圧接される。これにより、接続部材と下板が摩擦圧接部（接合部）で接合されるとともに、上板が接続部材の頭部と下板との問で固定される。
For example, Patent Document 1 discloses a technique for joining two plate materials having different strengths, such as an aluminum plate and a steel plate, by a friction welding process using a joining element such as a rivet (i.e., a connecting member having a head and a shaft). Specifically, the technique discloses joining two plate materials having different strengths through the following process.
That is, two plates are stacked together with the plate with the lesser strength as the upper plate, a connecting member supported by a holder is set on the upper surface of the upper plate, and the connecting member is moved downward while rotating and pressed toward the inside of the upper plate. At this time, strong friction is generated between the connecting member and the upper plate due to the rotation of the connecting member, and the tip of the connecting member is heated, softening the upper plate and enabling the connecting member to enter the upper plate.
In this way, when the tip of the connecting member, which is rotating and entering the upper plate, reaches the upper surface of the lower plate, a friction welding process proceeds between the shaft of the connecting member and the lower plate, and the shaft of the connecting member and the lower plate are frictionally welded together. As a result, the connecting member and the lower plate are joined at the friction welded part (joint part), and the upper plate is fixed between the head of the connecting member and the lower plate.
また、上記のような摩擦圧接により接続部材を介して上下の板を接合した継手として、例えば、特許文献２には、下板として引張強さ１０００ＭＰａ以上の高強度鋼板、接続部材として炭素を０．１７～０．４５％、クロムを０．７０～１．５％、モリブデンを０．１５～０．８０％含む合金スチールを用いた接合継手が開示されている。 As an example of a joint in which upper and lower plates are joined via a connecting member by friction welding as described above, Patent Document 2 discloses a joint in which the lower plate is a high-strength steel plate with a tensile strength of 1000 MPa or more, and the connecting member is an alloy steel containing 0.17 to 0.45% carbon, 0.70 to 1.5% chromium, and 0.15 to 0.80% molybdenum.
摩擦圧接にて鋼同士又は鋼とほかの金属材料を接合して破断強度試験を実施すると、特に強度が７８０ＭＰａを超える高強度鋼板では変形能が小さい傾向があるため継手強度が不足し易い。
特許文献２では、摩擦圧接接合継手の下板として引張強さ１０００ＭＰａ以上の高強度鋼板を用いることが開示されているが、高強度鋼板の成分及び組織について何ら記載されてなく、高強度鋼板を用いた場合の継手強度の低下について考慮されていない。
When steel is joined to another metal material or steel is joined to another metal material by friction welding and a fracture strength test is carried out, the joint strength is easily insufficient, since high-strength steel plates, particularly those with strengths exceeding 780 MPa, tend to have low deformability.
Patent Document 2 discloses the use of a high-strength steel plate having a tensile strength of 1000 MPa or more as the lower plate of a friction welded joint. However, there is no description of the components and structure of the high-strength steel plate, and no consideration is given to the decrease in joint strength when a high-strength steel plate is used.
本開示は、引張強さが高い鋼板を用いて摩擦圧接を行った場合に、継手強度が高い接合継手が得られる摩擦圧接用鋼板並びにそれを用いた複合部材及び自動車用部材を提供することを目的とする。 The purpose of this disclosure is to provide a steel plate for friction welding that can produce a joint with high joint strength when friction welding is performed using a steel plate with high tensile strength, as well as a composite member and an automotive member that use the same.
上記目的を達成するための本開示の要旨は次の通りである。
＜１＞ 質量％で、
Ｃ：０．１０～０．７０％、
Ｓｉ：０．１０～３．５０％、
Ｍｎ：０．５０～５．００％、
Ｐ：０．０２０％以下、
Ｓ：０．０５０％以下、
Ａｌ：３．０００％以下、及び
Ｎ：０．０１０％以下であり、
残部が、Ｆｅ及び不純物からなる鋼成分を有し、
マルテンサイト、焼戻しマルテンサイト、ラス状ベイナイト、及び焼戻しラス状ベイナイトからなる群より選ばれる１種又は２種以上の組織を含み、前記組織の合計分率が６０％以上である鋼組織を有し、
引張強さが７８０ＭＰａ以上である、
摩擦圧接用鋼板。
＜２＞ 前記Ｆｅの一部に代えて、質量％で、
Ｔｉ：０．３０％以下、
Ｎｂ：０．３０％以下、及び、
Ｖ：０．３０％以下
からなる群より選ばれる１種又は２種以上を含む＜１＞に記載の摩擦圧接用鋼板。
＜３＞ 前記Ｆｅの一部に代えて、質量％で、
Ｃｒ：５．０％以下、及び、Ｍｏ：２．０％以下の１種又は２種を含む＜１＞又は＜２＞に記載の摩擦圧接用鋼板。
＜４＞ 前記Ｆｅの一部に代えて、質量％で、Ｃｕ：２．０％以下、及び、Ｎｉ：１０．０％以下の１種又は２種を含む＜１＞～＜３＞のいずれか１つに記載の摩擦圧接用鋼板。
＜５＞ 前記Ｆｅの一部に代えて、質量％で、Ｂ：０．０２０％以下を含む＜１＞～＜４＞のいずれか１つに記載の摩擦圧接用鋼板。
＜６＞ 前記Ｆｅの一部に代えて、質量％で、
Ｃａ：０．００３０％以下、
ＲＥＭ：０．０５０％以下、
Ｍｇ：０．０５％以下、及び
Ｚｒ：０．０５％以下
からなる群より選ばれる１種又は２種以上を含む＜１＞～＜５＞のいずれか１つに記載の摩擦圧接用鋼板。
＜７＞ 表面にＺｎ及びＡｌの少なくとも一方を含むめっき層が形成されている＜１＞～＜６＞のいずれか１つに記載の摩擦圧接用鋼板。
＜８＞ 第１の板材と、
＜１＞～＜７＞のいずれか１つに記載の摩擦圧接用鋼板であって、前記第１の板材に重ね合わされた第２の板材と、
頭部及び軸部を有し、前記第１の板材と前記第２の板材とを接続する接続部材と、
を含み、
前記接続部材の前記軸部が前記第１の板材を貫通して前記軸部の先端部が前記第２の板材と接合されており、前記第１の板材が前記接続部材の前記頭部と前記第２の板材との間で固定された構造を有する、
複合部材。
＜９＞ ＜８＞に記載の複合部材を備える自動車用部材。
The gist of the present disclosure to achieve the above object is as follows.
<1> In mass%,
C: 0.10 to 0.70%,
Si: 0.10 to 3.50%,
Mn: 0.50 to 5.00%,
P: 0.020% or less,
S: 0.050% or less,
Al: 3.000% or less, and N: 0.010% or less;
The balance has a steel composition consisting of Fe and impurities,
The steel has a steel structure including one or more structures selected from the group consisting of martensite, tempered martensite, lath bainite, and tempered lath bainite, the total fraction of the structures being 60% or more;
The tensile strength is 780 MPa or more.
Steel plate for friction welding.
<2> In place of a part of the Fe,
Ti: 0.30% or less,
Nb: 0.30% or less; and
The steel plate for friction welding according to <1>, further comprising one or more selected from the group consisting of: V: 0.30% or less.
<3> In place of a part of the Fe,
The steel plate for friction welding according to <1> or <2>, comprising one or both of Cr: 5.0% or less and Mo: 2.0% or less.
<4> The steel plate for friction welding according to any one of <1> to <3>, containing, in mass%, one or two of Cu: 2.0% or less and Ni: 10.0% or less instead of a part of the Fe.
<5> The steel plate for friction welding according to any one of <1> to <4>, further comprising, in mass%, 0.020% or less of B in place of a portion of the Fe.
<6> In place of a part of the Fe,
Ca: 0.0030% or less,
REM: 0.050% or less,
The steel plate for friction welding according to any one of <1> to <5>, comprising one or more selected from the group consisting of Mg: 0.05% or less, and Zr: 0.05% or less.
<7> A steel sheet for friction welding according to any one of <1> to <6>, wherein a plating layer containing at least one of Zn and Al is formed on the surface.
<8> A first plate material;
A steel plate for friction welding according to any one of <1> to <7>, comprising: a second plate material overlapped on the first plate material;
a connecting member having a head portion and a shaft portion, the connecting member connecting the first plate material and the second plate material;
Including,
The shaft portion of the connection member penetrates the first plate material, and a tip portion of the shaft portion is joined to the second plate material, and the first plate material has a structure in which the head portion of the connection member and the second plate material are fixed.
Composite material.
<9> An automobile member comprising the composite member according to <8>.
本開示によれば、引張強さが高い鋼板を用いて摩擦圧接を行った場合に、継手強度が高い接合継手が得られる摩擦圧接用鋼板並びにそれを用いた複合部材及び自動車用部材が提供される。 According to the present disclosure, a steel plate for friction welding that can obtain a joint with high joint strength when friction welding is performed using a steel plate with high tensile strength, as well as a composite member and an automotive member using the same are provided.
本開示の一例である実施形態について説明する。
なお、本開示において、各元素の含有量の「％」表示は「質量％」を意味する。また、本開示において、「～」を用いて表される数値範囲は、特に断りの無い限り、「～」の前後に記載される数値を下限値及び上限値として含む範囲を意味する。また、「～」の前後に記載される数値に「超」又は「未満」が付されている場合の数値範囲は、これら数値を下限値又は上限値として含まない範囲を意味する。
本開示に段階的に記載されている数値範囲において、ある段階的な数値範囲の上限値又は下限値は、他の段階的な記載の数値範囲の上限値又は下限値に置き換えてもよく、また、実施例に示されている値に置き換えてもよい。
また、「工程」との用語は、独立した工程だけではなく、他の工程と明確に区別できない場合であってもその工程の所期の目的が達成されれば、本用語に含まれる。
An embodiment that is an example of the present disclosure will be described.
In this disclosure, the "%" designation for the content of each element means "mass %." In this disclosure, a numerical range expressed using "to" means a range that includes the numerical values written before and after "to" as the lower and upper limits, unless otherwise specified. In addition, when the numerical values written before and after "to" are followed by "greater than" or "less than," the numerical range does not include these numerical values as the lower or upper limit.
In the numerical ranges described in stages in this disclosure, the upper or lower limit of a certain numerical range may be replaced by the upper or lower limit of another numerical range described in stages, or may be replaced by a value shown in the examples.
In addition, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved.
本発明者らは、鋼板にリベット等の接続部材を摩擦圧接によって接合して接合継手を製造する場合、Ｃ含有量が比較的多い高強度鋼板を用いると継手強度が不足する原因について詳細に調べたところ、接合部近傍の二相域（フェライト相及びオーステナイト相）に加熱された領域（以下、「二相域加熱部」と称する。）における軟質相（主にフェライト相）と硬質相（主にマルテンサイト相）との高い硬度差が、軟質相と硬質相の界面などにひずみを集中させることが原因と考えられた。ここで、軟質相とは、二相域加熱部において、硬質相（主にマルテンサイト相）よりも硬さが低い相を指す。
特に、接合継手の二相域加熱部の軟質相がアスペクト比の小さい塊状の形状であると、継手強度が低下することが明らかになった。
そこで、本発明者らは、接合部に生じる二相域加熱部の軟質相を所定の形状、好ましくはアスペクト比が５以上となる針状に制御することで、局所的なひずみ集中を緩和し、接合継手としての継手強度が向上することを見出した。
The present inventors have investigated in detail the cause of insufficient joint strength when a high-strength steel plate with a relatively high C content is used in manufacturing a joint by friction welding a connecting member such as a rivet to a steel plate, and have concluded that the cause is that the high hardness difference between the soft phase (mainly the ferrite phase) and the hard phase (mainly the martensite phase) in the region heated to the two-phase region (ferrite phase and austenite phase) near the joint (hereinafter referred to as the "two-phase region heated portion") causes strain to concentrate at the interface between the soft phase and the hard phase, etc. Here, the soft phase refers to a phase in the two-phase region heated portion that is lower in hardness than the hard phase (mainly the martensite phase).
In particular, it was found that when the soft phase in the two-phase region heated portion of the welded joint has a blocky shape with a small aspect ratio, the joint strength decreases.
Therefore, the inventors discovered that by controlling the soft phase in the two-phase region heated portion that occurs in the joint to a predetermined shape, preferably a needle shape with an aspect ratio of 5 or more, it is possible to alleviate local strain concentration and improve the joint strength of the joint.
一方、本発明者らは、摩擦圧接による接合に用いる鋼板の接合前後の組織形態を調査した。図１は接合前の鋼板の組織の一例を示すＳＥＭ画像であり、Ａは主に塊状のフェライトとマルテンサイトからなる組織、Ｂは主に焼戻しマルテンサイトと焼戻しラス状ベイナイトからなる組織である。そして、組織Ａを有する鋼板を用いて摩擦圧接を行った接合継手と、組織Ｂを有する鋼板を用いて摩擦圧接を行った接合継手について、それぞれ接合部における領域ａ、ｂの組織を観察した。
図２は、図１に示す組織Ａを有する鋼板を用いて摩擦圧接した接合継手の板厚方向の断面を示すＳＥＭ画像であり、図３は、図２に示す接合部の領域ａ及び領域ｂの各組織を示すＳＥＭ画像である。
また、図４は、図１に示す組織Ｂを有する鋼板を用いて摩擦圧接した接合継手の板厚方向の断面を示すＳＥＭ画像であり、図５は、図４に示す接合部の領域ａ及び領域ｂの各組織を示すＳＥＭ画像である。
なお、図２及び図４において、１０は上板（アルミニウム合金）、２０は下板（鋼板）、３０は接続部材（リベット）であり、３２はリベットの頭部、３４はリベットの軸部、４０は下板２０と接続部材３０との接合部である。また、図２及び図４における破線は、Ａｃ１点近傍まで加熱されたと考えられる領域の境界を示している。
図１の組織Ａと図３の領域ａの組織との対比、及び、図１の組織Ｂと図５の領域ａの組織との対比から明らかなように、いずれの鋼板を用いた場合でも、接合部は非溶融かつ急速加熱冷却によって形成されるため、接合後の二相域加熱部の組織形態は、接合前の鋼板の組織形態に影響を受ける。そのため、接合前の鋼板の組織を制御しておくことで、接合後の組織を制御することがある程度可能であることが分かった。
On the other hand, the present inventors investigated the microstructural morphology of steel plates used for joining by friction welding before and after joining. Figure 1 is an SEM image showing an example of the structure of a steel plate before joining, where A is a structure mainly composed of massive ferrite and martensite, and B is a structure mainly composed of tempered martensite and tempered lath-shaped bainite. Then, the microstructures of regions a and b in the joints of a joint friction-welded using a steel plate having structure A and a joint friction-welded using a steel plate having structure B were observed.
FIG. 2 is an SEM image showing a cross section in the plate thickness direction of a friction-welded joint using a steel plate having the structure A shown in FIG. 1, and FIG. 3 is an SEM image showing the structures of region a and region b of the joint shown in FIG. 2.
FIG. 4 is an SEM image showing a cross section in the plate thickness direction of a friction-welded joint using a steel plate having the structure B shown in FIG. 1, and FIG. 5 is an SEM image showing the structures of region a and region b of the joint shown in FIG. 4.
2 and 4, 10 is an upper plate (aluminum alloy), 20 is a lower plate (steel plate), 30 is a connecting member (rivet), 32 is a rivet head, 34 is a rivet shaft, and 40 is a joint between the lower plate 20 and the connecting member 30. The dashed lines in Fig. 2 and 4 indicate the boundaries of the region that is considered to have been heated to near point A c1 .
As is clear from the comparison of the structure A in Fig. 1 with the structure of region a in Fig. 3 and the comparison of the structure B in Fig. 1 with the structure of region a in Fig. 5, regardless of which steel plate is used, the joint is formed by non-melting and rapid heating and cooling, so that the structural morphology of the two-phase region heated portion after joining is affected by the structural morphology of the steel plate before joining. Therefore, it was found that it is possible to some extent to control the structure after joining by controlling the structure of the steel plate before joining.
そして、接合継手の二相域加熱部において上述の針状の軟質相（針状軟質相）が分散した組織形態を実現するには、接合前の組織がラス状となる組織、具体的には、マルテンサイト、焼戻しマルテンサイト、ラス状のベイナイト、及び焼戻しラス状ベイナイトからなる群より選ばれる１種又は２種以上の組織を含み、これらの組織の合計分率が６０％以上となる鋼板を用いることが有効であり、このような鋼板を用いて摩擦圧接により接合した接合継手であれば、高い継手強度が得られることを実験的に見出し、本開示を完成するに至った。
すなわち、本開示に係る摩擦圧接用鋼板は、質量％で、
Ｃ：０．１０～０．７０％、
Ｓｉ：０．１０～３．５０％、
Ｍｎ：０．５０～５．００％、
Ｐ：０．０２０％以下、
Ｓ：０．０５０％以下、
Ａｌ：３．０００％以下、及び
Ｎ：０．０１０％以下であり、
残部が、Ｆｅ及び不純物からなる鋼成分を有し、
マルテンサイト、焼戻しマルテンサイト、ラス状ベイナイト、及び焼戻しラス状ベイナイトからなる群より選ばれる１種又は２種以上の組織を含み、前記組織の合計分率が６０％以上である鋼組織を有し、
引張強さが７８０ＭＰａ以上である、摩擦圧接用鋼板である。
In order to realize a structural morphology in which the above-mentioned needle-shaped soft phase (needle-shaped soft phase) is dispersed in the two-phase region heated portion of the joined joint, it is effective to use a steel plate having a lath-shaped structure before joining, specifically, a structure containing one or more types of structures selected from the group consisting of martensite, tempered martensite, lath-shaped bainite, and tempered lath-shaped bainite, and in which the total fraction of these structures is 60% or more. It was experimentally found that a joined joint joined by friction welding using such a steel plate can obtain high joint strength, and this led to the completion of the present disclosure.
That is, the steel plate for friction welding according to the present disclosure comprises, in mass%,
C: 0.10 to 0.70%,
Si: 0.10 to 3.50%,
Mn: 0.50 to 5.00%,
P: 0.020% or less,
S: 0.050% or less,
Al: 3.000% or less, and N: 0.010% or less;
The balance has a steel composition consisting of Fe and impurities,
The steel has a steel structure including one or more structures selected from the group consisting of martensite, tempered martensite, lath bainite, and tempered lath bainite, the total fraction of the structures being 60% or more;
The steel plate for friction welding has a tensile strength of 780 MPa or more.
［鋼成分］
本開示に係る摩擦圧接用鋼板の鋼成分について具体的に説明する。
本開示に係る摩擦圧接用鋼板の鋼成分は、Ｃ：０．１０～０．７０％、Ｓｉ：０．１０～３．５０％、Ｍｎ：０．５０～５．００％、Ｐ：０．０２０％以下、Ｓ：０．０５０％以下、Ａｌ：３．０００％以下、及びＮ：０．０１０％以下であり、残部が、Ｆｅ及び不純物からなる。また、本開示に係る摩擦圧接用鋼板は、上記鋼成分におけるＦｅの一部に代えて、質量％で、
Ｔｉ：０．３０％以下、
Ｎｂ：０．３０％以下、
Ｖ：０．３０％以下、
Ｃｒ：５．０％以下、
Ｍｏ：２．０％以下、
Ｃｕ：２．０％以下、
Ｎｉ：１０．０％以下、
Ｂ：０．０２０％以下、
Ｃａ：０．００３％以下、
ＲＥＭ：０．０５％以下、
Ｍｇ：０．０５０％以下、及び
Ｚｒ：０．０５０％以下
からなる群より選ばれる１種又は２種以上を含んでもよい。
以下、各元素の含有量を限定した理由について説明する。
[Steel composition]
The steel components of the steel plate for friction welding according to the present disclosure will be specifically described.
The steel components of the steel plate for friction welding according to the present disclosure are C: 0.10 to 0.70%, Si: 0.10 to 3.50%, Mn: 0.50 to 5.00%, P: 0.020% or less, S: 0.050% or less, Al: 3.000% or less, and N: 0.010% or less, with the balance being Fe and impurities. Further, the steel plate for friction welding according to the present disclosure contains, in mass %, the following instead of a part of the Fe in the above steel components:
Ti: 0.30% or less,
Nb: 0.30% or less,
V: 0.30% or less,
Cr: 5.0% or less,
Mo: 2.0% or less,
Cu: 2.0% or less,
Ni: 10.0% or less,
B: 0.020% or less,
Ca: 0.003% or less,
REM: 0.05% or less,
One or more selected from the group consisting of Mg: 0.050% or less, and Zr: 0.050% or less may be contained.
The reasons for limiting the content of each element will be explained below.
Ｃ：０．１０～０．７０％
Ｃは、鋼の焼入れ性を高め、強度向上に寄与する元素である。Ｃ含有量が０．１０％未満であると、高い引張強さが得られないので、下限を０．１０％とする。好ましい下限は０．１５％である。一方、Ｃ含有量が０．７０％を超えると、強度が向上しすぎて加工性が低下するとともに継手強度も低下するので、上限を０．７０％とする。強度と加工性をバランスよく確保するには、Ｃ含有量は０．１５～０．５５％が好ましい。
C: 0.10 to 0.70%
C is an element that improves the hardenability of steel and contributes to improving strength. If the C content is less than 0.10%, high tensile strength cannot be obtained, so the lower limit is set to 0.10%. The preferable lower limit is 0.15%. On the other hand, if the C content exceeds 0.70%, the strength is improved too much, and the workability and joint strength are also reduced, so the upper limit is set to 0.70%. To ensure a good balance between strength and workability, the C content is preferably 0.15 to 0.55%.
Ｓｉ：０．１０～３．５０％
Ｓｉは、固溶強化及び組織強化により、鋼の強度を高める元素である。Ｓｉ含有量が０．１％未満であると、高い引張強さが得られないので、下限を０．１０％とする。一方、Ｓｉ含有量が３．５０％を超えると、加工性が低下するとともに継手強度も低下するので、上限を３．５０％とする。強度と加工性をバランスよく確保するには、０．５０～２．００％が好ましい。
Si: 0.10 to 3.50%
Silicon is an element that increases the strength of steel through solid solution strengthening and microstructural strengthening. If the silicon content is less than 0.1%, high tensile strength cannot be obtained, so the lower limit is set to 0.10%. On the other hand, if the silicon content exceeds 3.50%, the workability and joint strength decrease, so the upper limit is set to 3.50%. To ensure a good balance between strength and workability, a silicon content of 0.50 to 2.00% is preferable.
Ｍｎ：０．５０～５．００％
Ｍｎは、鋼の強度を高める元素である。Ｍｎ含有量が０．５０％未満であると、高い引張強さが得られないので、下限を０．５０％とする。一方、Ｍｎ含有量が５．００％を超えると、加工性が劣化するとともに継手強度も低下するので、上限を５．００％とする。強度と加工性をバランスよく確保するには、１．００～２．８０％が好ましい。より好ましくは、１．５０～２．５０％である。
Mn: 0.50 to 5.00%
Mn is an element that increases the strength of steel. If the Mn content is less than 0.50%, high tensile strength cannot be obtained, so the lower limit is set to 0.50%. On the other hand, if the Mn content exceeds 5.00%, the workability deteriorates and the joint strength also decreases, so the upper limit is set to 5.00%. In order to ensure a good balance between strength and workability, a Mn content of 1.00 to 2.80% is preferable. More preferably, it is 1.50 to 2.50%.
Ｐ：０．０２０％以下
Ｐは、不純物であり、脆化を起こす元素である。Ｐ含有量が０．０２０％を超えると、継手強度を得ることが難しいので、上限を０．０２０％とする。
P: 0.020% or less P is an impurity and an element that causes embrittlement. If the P content exceeds 0.020%, it becomes difficult to obtain sufficient joint strength, so the upper limit is set to 0.020%.
Ｓ：０．０５０％以下
Ｓは、Ｐと同様に、不純物であり脆化をおこす元素である。また、Ｓは、鋼中で粗大なＭｎＳを形成し、鋼の加工性を低下させるとともに継手強度も低下させる元素である。Ｓ含有量が０．０５０％を超えると、所要の継手強度を得ることが難しく、また、鋼の加工性が低下するので、上限を０．０５０％とする。
S: 0.050% or less S, like P, is an impurity and an element that causes embrittlement. S also forms coarse MnS in steel, which reduces the workability of steel and also reduces joint strength. If the S content exceeds 0.050%, it is difficult to obtain the required joint strength, and the workability of steel decreases, so the upper limit is set to 0.050%.
Ａｌ：３．０００％以下
Ａｌは、脱酸作用をなす元素であり、また、フェライトを安定化し、セメンタイトの析出を抑制する元素である。Ａｌは、脱酸、及び、鋼組織の制御のため含有させるが、Ａｌは酸化し易く、Ａｌ含有量が３．０００％を超えると、介在物が増加して加工性が低下するとともに継手強度も低下するので、上限を３．０００％とする。加工性を確保する点で、好ましい上限は１．２００％である。脱酸、及び、鋼組織の制御のため、Ａｌ含有量の好ましい下限値は、０．００１％である。
Al: 3.000% or less Al is an element that has a deoxidizing effect, stabilizes ferrite, and suppresses the precipitation of cementite. Al is contained for deoxidation and control of the steel structure, but Al is easily oxidized, and if the Al content exceeds 3.000%, inclusions increase, workability decreases, and joint strength also decreases, so the upper limit is set to 3.000%. In terms of ensuring workability, the preferred upper limit is 1.200%. In order to control deoxidation and the steel structure, the preferred lower limit of the Al content is 0.001%.
Ｎ：０．０１０％以下
Ｎは、鋼板の強度を高める元素であるが、鋼中で粗大な窒化物を形成し、鋼の成形性を劣化させる作用をなす元素である。Ｎ含有量が０．０１０％を超えると、鋼の成形性の劣化、継手強度の低下が顕著となるので、上限を０．０１０％とする。
N: 0.010% or less N is an element that increases the strength of steel plate, but also forms coarse nitrides in steel, which deteriorates the formability of steel. If the N content exceeds 0.010%, the deterioration of the formability of steel and the decrease in joint strength become significant, so the upper limit is set to 0.010%.
残部：Ｆｅ及び不純物
残部は、Ｆｅ及び不純物である。不純物とは、鉱石、スクラップ等の原材料に含まれる成分、又は、製造の過程で混入する成分が例示され、意図的に摩擦圧接用鋼板に含有させたものではない成分を指す。
Balance: Fe and impurities The balance is Fe and impurities. Examples of impurities include components contained in raw materials such as ores and scraps, or components mixed in during the manufacturing process, and refer to components that are not intentionally contained in the steel plate for friction welding.
本開示に係る摩擦圧接用鋼板は、Ｆｅの一部に代えて上記以外の元素（任意元素）を含んでもよい。以下に本開示の摩擦圧接用鋼板に含み得る任意元素について説明する。なお、以下の任意元素は含まない、すなわち含有量が０％でもよいし、含む場合の下限値は０％超であってもよい。 The steel plate for friction welding according to the present disclosure may contain elements (optional elements) other than those mentioned above in place of a portion of the Fe. The optional elements that may be contained in the steel plate for friction welding according to the present disclosure are described below. Note that the following optional elements may not be contained, i.e., the content may be 0%, or if contained, the lower limit may be greater than 0%.
本開示に係る摩擦圧接用鋼板は、鋼板組織の粗大化を抑制するため、Ｆｅの一部に代えて、質量％で、
Ｔｉ：０．３０％以下、
Ｎｂ：０．３０％以下、及び、
Ｖ：０．３０％以下
からなる群より選ばれる１種又は２種以上を含有してもよい。
In order to suppress coarsening of the steel plate structure, the steel plate for friction welding according to the present disclosure contains, in mass %, in place of a part of Fe,
Ti: 0.30% or less,
Nb: 0.30% or less; and
V: 0.30% or less. One or more elements selected from the group consisting of V may be contained.
Ｔｉ：０．３０％以下
Ｔｉは、析出物を形成し、鋼板組織を細粒とする元素である。含有効果を得るため、０．００１％以上含有することが好ましい。より好ましくは０．０１％以上である。一方、過剰に含有すると、製造性が低下し、加工時に割れが生じるだけでなく継手強度の低下も起こすので、０．３０％を上限とすることが好ましく、より好ましくは０．２０％以下である。
Ti: 0.30% or less Ti is an element that forms precipitates and makes the steel sheet structure fine-grained. In order to obtain the effect of containing Ti, it is preferable to contain 0.001% or more. More preferably, it is 0.01% or more. On the other hand, if it is contained excessively, not only the manufacturability is reduced, cracks are generated during processing, but also the joint strength is reduced, so that the upper limit is preferably 0.30%, and more preferably 0.20% or less.
Ｎｂ：０．３０％以下
Ｎｂは、微細な炭窒化物を形成し結晶粒の粗大化を抑制する元素である。含有効果を得るため、０．００１％以上含有することが好ましい。より好ましくは０．０１％以上である。過剰に含有すると、靭性を阻害し製造困難になるだけでなく継手強度低下を引き起こすため、上限を０．３０％とすることが好ましく、より好ましくは０．２０％以下である。
Nb: 0.30% or less Nb is an element that forms fine carbonitrides and suppresses the coarsening of crystal grains. In order to obtain the effect of containing Nb, it is preferable to contain 0.001% or more. More preferably, it is 0.01% or more. If contained excessively, it not only inhibits toughness and makes manufacturing difficult, but also causes a decrease in joint strength, so the upper limit is preferably set to 0.30%, and more preferably 0.20% or less.
Ｖ：０．３０％以下
Ｖは、微細な炭窒化物を形成し結晶粒の粗大化を抑制する元素である。含有効果を得るため、０．００１％以上含有することが好ましい。より好ましくは０．０３％以上である。過剰に含有すると、靭性を阻害し製造困難になるだけでなく継手強度低下を引き起こすため、上限を０．３０％とすることが好ましく、より好ましくは０．２５％以下である。
V: 0.30% or less V is an element that forms fine carbonitrides and suppresses the coarsening of crystal grains. In order to obtain the effect of containing V, it is preferable to contain 0.001% or more. More preferably, it is 0.03% or more. If contained excessively, it not only inhibits toughness and makes manufacturing difficult, but also causes a decrease in joint strength, so the upper limit is preferably set to 0.30%, and more preferably 0.25% or less.
Ｃｒ：５．０％以下
Ｍｏ：２．０％以下
本開示に係る摩擦圧接用鋼板は、鋼の強度の向上のため、Ｆｅの一部に代えて、質量％で、Ｃｒ：５．０％以下、及び、Ｍｏ：２．０％以下の１種又は２種を含有してもよい。
Ｃｒ及びＭｏは、鋼の強度の向上に寄与する元素である。含有効果を得るため、０．００１％以上含有することが好ましい。より好ましくは０．０５％以上である。ただし、Ｃｒ含有量が５．０％を超え、又はＭｏ含有量が２．０％を超えると、酸洗時や熱間加工時に支障が生じることがあるだけでなく継手強度の低下を招くので、Ｃｒ含有量の上限は５．０％とすることが好ましく、Ｍｏ含有量の上限は２．０％とすることが好ましい。
Cr: 5.0% or less Mo: 2.0% or less The steel plate for friction welding according to the present disclosure may contain, in mass %, one or both of Cr: 5.0% or less and Mo: 2.0% or less in place of a portion of Fe in order to improve the strength of the steel.
Cr and Mo are elements that contribute to improving the strength of steel. In order to obtain the effect of inclusion, it is preferable to contain 0.001% or more. More preferably, it is 0.05% or more. However, if the Cr content exceeds 5.0% or the Mo content exceeds 2.0%, not only may problems occur during pickling or hot working, but also joint strength may decrease, so the upper limit of the Cr content is preferably 5.0% and the upper limit of the Mo content is preferably 2.0%.
Ｃｕ：２．０％以下
Ｎｉ：１０．０％以下
本開示に係る摩擦圧接用鋼板は、鋼の強度向上のため、Ｆｅの一部に代えて、質量％で、Ｃｕ：２．０％以下、及び、Ｎｉ：１０．０％以下の１種又は２種を含有してもよい。
Ｃｕ及びＮｉは、鋼の強度の向上に寄与する元素である。含有効果を得るため、０．００１％以上含有することが好ましい。より好ましくは０．１０％以上である。ただし、Ｃｕ量が２．０％を超え、Ｎｉ含有量が１０．０％を超えると、酸洗時や熱間加工時に支障が生じることがあるだけでなく継手強度の低下を招くことがあるので、Ｃｕ量の上限は２．０％とすることが好ましく、Ｎｉ含有量の上限は１０．０％とすることが好ましい。
Cu: 2.0% or less Ni: 10.0% or less The steel plate for friction welding according to the present disclosure may contain, in mass %, one or both of Cu: 2.0% or less and Ni: 10.0% or less in place of a portion of Fe in order to improve the strength of the steel.
Cu and Ni are elements that contribute to improving the strength of steel. In order to obtain the effect of inclusion, it is preferable to contain 0.001% or more. More preferably, it is 0.10% or more. However, if the Cu content exceeds 2.0% and the Ni content exceeds 10.0%, not only may problems occur during pickling or hot working, but also joint strength may decrease, so the upper limit of the Cu content is preferably 2.0% and the upper limit of the Ni content is preferably 10.0%.
本開示に係る摩擦圧接用鋼板は、熱間圧延工程における成形性の向上のため、Ｆｅの一部に代えて、質量％で、
Ｃａ：０．００３％以下、
ＲＥＭ０．０５％以下、
Ｍｇ：０．０５０％以下、及び
Ｚｒ：０．０５０％以下からなる群より選ばれる１種又は２種以上を含有してもよい。
In order to improve formability in a hot rolling process, the steel plate for friction welding according to the present disclosure contains, in mass% by replacing a part of Fe,
Ca: 0.003% or less,
REM 0.05% or less,
One or more selected from the group consisting of Mg: 0.050% or less, and Zr: 0.050% or less may be contained.
Ｃａ、ＲＥＭ（ｒａｒｅ ｅａｒｔｈ ｍｅｔａｌ）、Ｍｇ、及びＺｒは、脱酸後の酸化物や、熱間圧延鋼板中に存在する硫化物を微細化し、成形性の向上に寄与する元素である。ただし、Ｃａの含有量が０．００３％を超え、ＲＥＭの含有量が０．０５％を超え、Ｍｇ、又はＺｒの各含有量が０．０５％を超えると、鋼の加工性が低下する。そのため、Ｃａ含有量の上限を０．００３％とし、ＲＥＭ含有量の上限を０．０５％とし、Ｍｇ、及びＺｒの各含有量の上限を０．０５％とすることが好ましい。
なお、含有効果を得るため、Ｃａ含有量は０．０００５％以上、ＲＥＭは０．００１ ％以上、Ｍｇは０．００１％以上、Ｚｒは０．００１％以上とすることが好ましい。
Ca, REM (rare earth metal), Mg, and Zr are elements that refine oxides after deoxidation and sulfides present in hot-rolled steel sheets, and contribute to improving formability. However, if the Ca content exceeds 0.003%, the REM content exceeds 0.05%, and each of the Mg and Zr contents exceeds 0.05%, the workability of the steel decreases. Therefore, it is preferable to set the upper limit of the Ca content to 0.003%, the upper limit of the REM content to 0.05%, and the upper limit of each of the Mg and Zr contents to 0.05%.
In order to obtain the effects of each of these elements, it is preferable that the Ca content be 0.0005% or more, the REM content be 0.001% or more, the Mg content be 0.001% or more, and the Zr content be 0.001% or more.
なお、「ＲＥＭ」とはＳｃ、Ｙ、及びランタノイドの合計１７元素の総称であり、ＲＥＭの含有量はＲＥＭのうちの１種又は２種以上の元素の合計含有量を指す。また、ＲＥＭについては一般的にミッシュメタルに含有される。このため、例えば、ＲＥＭは、ＲＥＭの含有量が上記の範囲となるように、ミッシュメタルの形で含有させてもよい。 Note that "REM" is a general term for Sc, Y, and lanthanides, a total of 17 elements, and the REM content refers to the total content of one or more REM elements. REM is generally contained in misch metal. For this reason, for example, REM may be contained in the form of misch metal so that the REM content falls within the above range.
Ｂ：０．０２０％以下
本開示に係る摩擦圧接用鋼板は、Ｆｅの一部に代えて、質量％で、Ｂ：０．０２０％以下を含んでもよい。
Ｂは、粒界に偏析して粒界強度を高める元素である。含有効果を得るため、０．０００１％以上含有することが好ましく、より好ましくは０．０００８％以上である。一方、過剰に含有すると靭性を阻害し製造困難になるだけでなく継手強度低下を引き起こすため、上限を０．０２０％とすることが好ましく、より好ましくは０．０１０％以下である。
B: 0.020% or less The steel plate for friction welding according to the present disclosure may contain, in mass%, B: 0.020% or less in place of a portion of Fe.
B is an element that segregates at grain boundaries to increase grain boundary strength. In order to obtain the effect of containing B, it is preferable to contain 0.0001% or more, more preferably 0.0008% or more. On the other hand, if it is contained excessively, it not only inhibits toughness and makes manufacturing difficult, but also causes a decrease in joint strength, so the upper limit is preferably set to 0.020%, more preferably 0.010% or less.
［鋼組織］
本開示に係る摩擦圧接用鋼板の組織について説明する。
本開示に係る摩擦圧接用鋼板は、マルテンサイト、焼戻しマルテンサイト、ラス状ベイナイト（ラス状のベイナイト）、及び焼戻しラス状ベイナイト（ラス状のベイナイトを焼戻した組織）からなる群より選ばれる１種又は２種以上の組織を含み、前記組織の合計分率が６０％以上を占める鋼組織を有する。
本開示に係る摩擦圧接用鋼板の鋼成分は、前述したようにＣ含有量が０．１０～０．７０％であり、この範囲でＣを含む場合、マルテンサイト、焼戻しマルテンサイト、ラス状ベイナイト、及び焼戻しラス状ベイナイトは、いずれも、いわゆるラス状の組織となる。
摩擦圧接による接合継手の継手強度を向上させる観点から、マルテンサイト、焼戻しマルテンサイト、ラス状のベイナイト、及び焼戻しラス状ベイナイトからなる群より選ばれる１種又は２種以上の組織の合計分率は、７０％以上であることが好ましく、８０％以上であることがより好ましい。マルテンサイト、焼戻しマルテンサイト、ラス状のベイナイト、及び焼戻しラス状ベイナイトからなる群より選ばれる１種又は２種以上の組織の合計分率の上限は特に限定されず、１００％であってもよい。
また、摩擦圧接による接合継手の継手強度を向上させる観点から、マルテンサイト、焼戻しマルテンサイト、ラス状のベイナイト、及び焼戻しラス状ベイナイトのうち、マルテンサイト及び／又はラス状ベイナイトを含むことが好ましく、マルテンサイトの分率が最も高いことがさらに好ましい。焼戻しマルテンサイトや焼戻しラス状ベイナイトは、焼戻しによって鋼板の加工性を上げるが、接合中にさらに熱が加わることにより炭化物が粗大化してしまい靭性を落とす場合があるため、炭化物が析出していないマルテンサイトを多く含むことが好ましい。
[Steel structure]
The structure of the steel plate for friction welding according to the present disclosure will be described.
The steel plate for friction welding according to the present disclosure has a steel structure that includes one or more structures selected from the group consisting of martensite, tempered martensite, lath-shaped bainite (lath-shaped bainite), and tempered lath-shaped bainite (a structure obtained by tempering lath-shaped bainite), and the total fraction of the structures accounts for 60% or more.
As described above, the steel composition of the steel plate for friction welding according to the present disclosure has a C content of 0.10 to 0.70%, and when C is contained within this range, martensite, tempered martensite, lath-shaped bainite, and tempered lath-shaped bainite all become so-called lath-shaped structures.
From the viewpoint of improving the joint strength of a joint bonded by friction welding, the total fraction of one or more structures selected from the group consisting of martensite, tempered martensite, lath bainite, and tempered lath bainite is preferably 70% or more, and more preferably 80% or more. The upper limit of the total fraction of one or more structures selected from the group consisting of martensite, tempered martensite, lath bainite, and tempered lath bainite is not particularly limited, and may be 100%.
From the viewpoint of improving the joint strength of a joint formed by friction welding, it is preferable to contain martensite and/or lath-shaped bainite among martensite, tempered martensite, lath-shaped bainite, and tempered lath-shaped bainite, and it is further preferable that the fraction of martensite is the highest. Although tempered martensite and tempered lath-shaped bainite improve the workability of the steel sheet by tempering, the addition of additional heat during joining may cause the carbides to coarsen, reducing toughness, so it is preferable to contain a large amount of martensite in which no carbides are precipitated.
残部組織は特に限定されないが、マルテンサイト、焼戻しマルテンサイト、ラス状のベイナイト、及び焼戻しラス状ベイナイトからなる群より選ばれる１種又は２種以上の組織の合計分率が１００％未満である場合、残部組織は、フェライト、残留オーステナイト、及びパーライトからなる群より選ばれる１種又は２種以上であることが好ましく、フェライト及び残留オーステナイトを含むことがより好ましい。また、粗大な炭化物やその他の析出物などを含まない方が靱性確保の観点から好ましい。 The remaining structure is not particularly limited, but when the total fraction of one or more structures selected from the group consisting of martensite, tempered martensite, lath-shaped bainite, and tempered lath-shaped bainite is less than 100%, the remaining structure is preferably one or more structures selected from the group consisting of ferrite, retained austenite, and pearlite, and more preferably contains ferrite and retained austenite. In addition, from the viewpoint of ensuring toughness, it is preferable that the remaining structure does not contain coarse carbides or other precipitates.
摩擦圧接用鋼板における組織分率は、以下の方法によって求める。
まず、供試鋼板を厚さ方向に切断し、切断面を鏡面研磨し、３％ナイタール液で腐食して金属組織を顕出させた後、走査型電子顕微鏡にて倍率２０００倍で観察し、フェライト、ラス状ベイナイトおよび焼戻したラス状のベイナイト、パーライト組織を同定する。さらに、ラス状の組織で鉄炭化物を含む組織を焼戻しマルテンサイト、ラス状のベイナイトおよび焼戻したラス状のベイナイトとする。焼戻しマルテンサイトと焼戻したラス状のベイナイトは炭化物の析出位置およびその析出の方向から分離する。図８は焼戻しマルテンサイトの一例を示すＴＥＭ写真である。焼戻しマルテンサイトでは図８のように複数のバリアント、すなわち異なる方向に伸長した複数の鉄炭化物の析出が見られる。
一方、ラス状のベイナイトもしくは焼戻したラス状のベイナイトではセメンタイトの析出は一方向になっており焼戻しマルテンサイトと区別が可能である。焼戻したラス状のベイナイトとラス状のベイナイトとの区別は、本来の定義とはずれるが、便宜上、ベイニティックフェライト間のみに鉄炭化物を有するものはラス状のベイナイト、ベイニティックフェライト内に析出しているものを焼戻したラス状のベイナイトとする。
また、マルテンサイトについてはレペラーエッチングを行い光学顕微鏡で観察し、白色部をマルテンサイトとした。
本開示では、鋼板の組織分率は、上記のようにして切断面における各組織の面積率として求める。
The microstructure fraction in a steel plate for friction welding is determined by the following method.
First, the test steel plate is cut in the thickness direction, the cut surface is mirror-polished, and the metal structure is revealed by etching with 3% nital solution. The cut surface is then observed with a scanning electron microscope at a magnification of 2000 times to identify ferrite, lath-shaped bainite, tempered lath-shaped bainite, and pearlite structures. Furthermore, the lath-shaped structure containing iron carbide is called tempered martensite, lath-shaped bainite, and tempered lath-shaped bainite. Tempered martensite and tempered lath-shaped bainite are separated based on the carbide precipitation position and precipitation direction. Figure 8 is a TEM photograph showing an example of tempered martensite. In the tempered martensite, as shown in Figure 8, multiple variants, i.e., multiple iron carbide precipitations elongated in different directions, are observed.
On the other hand, in lath bainite or tempered lath bainite, cementite precipitates in one direction and can be distinguished from tempered martensite. The distinction between tempered lath bainite and lath bainite deviates from the original definition, but for convenience, lath bainite is defined as one that has iron carbides only between bainitic ferrite, and tempered lath bainite is defined as one that has iron carbides precipitated within bainitic ferrite.
Martensite was also examined by Leper etching and observation under an optical microscope, and the white areas were determined to be martensite.
In the present disclosure, the structure fraction of a steel sheet is determined as the area fraction of each structure in the cut surface as described above.
［引張強さ］
本開示に係る摩擦圧接用鋼板は、引張強さが７８０ＭＰａ以上である。これにより、本開示に係る摩擦圧接用鋼板を用いて摩擦圧接によって接合継手を製造した場合に継手強度が高く、母材（鋼板）が高強度の板状部材を得ることができる。本開示に係る摩擦圧接用鋼板の引張強さは、好ましくは、９８０ＭＰａ以上であり、より好ましくは１１８０ＭＰａ以上であり、さらに好ましくは１４７０ＭＰａ以上である。
[Tensile strength]
The friction welding steel plate according to the present disclosure has a tensile strength of 780 MPa or more. As a result, when a joint is produced by friction welding using the friction welding steel plate according to the present disclosure, a plate-shaped member having high joint strength and a high-strength base material (steel plate) can be obtained. The tensile strength of the friction welding steel plate according to the present disclosure is preferably 980 MPa or more, more preferably 1180 MPa or more, and even more preferably 1470 MPa or more.
［摩擦圧接用鋼板の製造方法］
本開示に係る摩擦圧接用鋼板の製造方法は特に限定されない。熱延鋼板でも冷延鋼板でもよい。例えば、以下の方法によって好適に製造することができる。
まず、転炉で上述した成分に調整された鋼を溶製して連続鋳造法によりスラブとし、スラブを高温状態のまま、あるいは、室温まで冷却した後、加熱炉に挿入し、１１００～１３００℃の温度範囲で加熱し、その後、８００～９５０℃の温度範囲で仕上げ圧延を行う。仕上げ圧延温度から５００～６５０℃まで水冷し、その後空冷する。
次いで、冷間圧延によって所望の厚みを有する鋼板にする。なお、本開示に係る摩擦圧接用鋼板の厚みは特に限定されず、摩擦圧接接合後の用途に応じて厚みを設定すればよい。例えば、１．０～３．５ｍｍの厚さにする。
[Method of manufacturing steel plate for friction welding]
The method for producing the steel plate for friction welding according to the present disclosure is not particularly limited. It may be a hot-rolled steel plate or a cold-rolled steel plate. For example, it can be suitably produced by the following method.
First, steel adjusted to the above-mentioned composition is melted in a converter and formed into a slab by a continuous casting method, and the slab is inserted into a heating furnace while still in a high temperature state or after being cooled to room temperature, and heated to a temperature range of 1100 to 1300° C., and then finish-rolled at a temperature range of 800 to 950° C. The slab is water-cooled from the finish-rolling temperature to 500 to 650° C., and then air-cooled.
Next, the steel plate is cold-rolled to a desired thickness. The thickness of the steel plate for friction welding according to the present disclosure is not particularly limited, and may be set according to the application after friction welding. For example, the thickness is set to 1.0 to 3.5 mm.
冷間圧延後、熱処理を行う。熱処理は７５０～８５０℃まで１０～１００℃／ｓｅｃで加熱し、その後、冷却や再加熱などの熱処理を行う。
マルテンサイト、ラス状のベイナイトの組織を作り込むのは、鋼板の組成によって、マルテンサイトやラス状のベイナイトが生成する冷却速度が異なるので、ＣＣＴ曲線やＴＴＴ曲線に基づいて行うのが好ましい。これにより、鋼板の厚さ方向の断面において、マルテンサイト、焼戻しマルテンサイト、ラス状のベイナイト、及び焼戻しラス状ベイナイトからなる群より選ばれる１種又は２種以上の組織を含み、これらの組織の面積率の合計が６０％以上である鋼組織を有し、引張強さが７８０ＭＰａ以上である摩擦圧接用鋼板を製造することができる。
After cold rolling, the sheet is heat-treated by heating to 750-850°C at 10-100°C/sec, and then cooled and reheated.
Since the cooling rate at which martensite and lath-shaped bainite are formed varies depending on the composition of the steel plate, it is preferable to create martensite and lath-shaped bainite structures based on a CCT curve or a TTT curve. This makes it possible to produce a steel plate for friction welding having a steel structure containing one or more structures selected from the group consisting of martensite, tempered martensite, lath-shaped bainite, and tempered lath-shaped bainite in a cross section in the thickness direction of the steel plate, the total area ratio of these structures being 60% or more, and having a tensile strength of 780 MPa or more.
本開示に係る摩擦圧接用鋼板は、表面にＺｎ及びＡｌの少なくとも一方を含むめっき層が形成されている摩擦圧接用めっき鋼板としてもよい。 The steel sheet for friction welding according to the present disclosure may be a plated steel sheet for friction welding having a plated layer containing at least one of Zn and Al formed on the surface.
上記の成分及び組織を有する鋼板にアルミめっき、アルミ－亜鉛めっき、亜鉛めっきを施してもよい。
アルミめっき工程、アルミ－亜鉛めっき工程、又は亜鉛めっき工程は常法を採用することができる。例えば、アルミめっきであれば、浴中Ｓｉ濃度は５～１２％が適しており、アルミ－亜鉛めっきでは、浴中Ｚｎ濃度は４０～５０％が適している。また、アルミめっき層中にＭｇやＺｎが混在しても、アルミ－亜鉛めっき層中にＭｇが混在してもよい。
なお、めっき工程における雰囲気については、無酸化炉を有する連続式めっき設備でも無酸化炉を有しない連続式めっき設備でも通常の条件とすることでめっき可能である。また、亜鉛めっき方法であれば、溶融亜鉛めっき、電気亜鉛めっき、合金化溶融亜鉛めっきなどいかなる方法を取ってもよい。
めっき前に鋼板表面に、ＮｉプレめっきやＦｅプレめっき、その他めっき性を向上させる金属プレめっきを施してもよい。また、めっき層表面に異種の金属めっきや無機系化合物又は有機系化合物の皮膜などを付与してもよい。
The steel sheet having the above-mentioned components and structure may be subjected to aluminum plating, aluminum-zinc plating, or zinc plating.
Conventional methods can be used for the aluminum plating step, aluminum-zinc plating step, or zinc plating step. For example, a Si concentration in the bath of 5 to 12% is suitable for aluminum plating, and a Zn concentration in the bath of 40 to 50% is suitable for aluminum-zinc plating. In addition, Mg and Zn may be mixed in the aluminum plating layer, or Mg may be mixed in the aluminum-zinc plating layer.
Regarding the atmosphere in the plating process, plating can be performed under normal conditions in a continuous plating facility with or without a non-oxidizing furnace. In addition, any zinc plating method, such as hot-dip galvanizing, electrolytic galvanizing, or alloyed hot-dip galvanizing, may be used.
Before plating, the steel sheet surface may be subjected to Ni pre-plating, Fe pre-plating, or other metal pre-plating that improves plating properties. Also, a different type of metal plating or a film of an inorganic compound or an organic compound may be applied to the surface of the plating layer.
例えば自動車用、家電用、建材用として使用される高強度表面処理鋼板は、その多くが溶融亜鉛めっき鋼板であり、溶融亜鉛めっきを施す場合は、通常、焼鈍とめっきが同じ設備（又は同一設備列）で同時に行われる。本開示に係る摩擦圧接用めっき鋼板を製造する場合、溶融亜鉛めっきのように、焼鈍及びめっきを同時に行った場合や、焼鈍の後、電気めっき、有機複合皮膜を施してもよい。 For example, many of the high-strength surface-treated steel sheets used for automobiles, home appliances, and building materials are hot-dip galvanized steel sheets, and when hot-dip galvanizing is performed, annealing and plating are usually performed simultaneously in the same equipment (or the same line of equipment). When manufacturing plated steel sheets for friction welding according to the present disclosure, annealing and plating may be performed simultaneously, as in hot-dip galvanizing, or electroplating or an organic composite coating may be applied after annealing.
めっき量としては、めっきの目的である防食作用を発揮させる観点から、３ｍｇ／ｍ２以上であることが好ましく、溶接時のブローホールなどの欠陥の発生を抑制する観点から、８００ｇ／ｍ２以下であることが好ましい。 The plating amount is preferably 3 mg/ m2 or more from the viewpoint of exerting the anticorrosive effect, which is the purpose of plating, and is preferably 800 g/m2 or less from the viewpoint of suppressing the occurrence of defects such as blowholes during welding.
［接合継手の製造方法］
本開示に係る摩擦圧接用鋼板は、他の部材を摩擦圧接によって接合して接合継手を製造するために用いられる。本開示に係る摩擦圧接用鋼板を用いて接合継手を製造する方法は特に限定されないが、例えば、上板（第１の板材）と下板（第２の板材）を重ね合わせ、リベット等の頭部と軸部を有する接続部材を用い、接続部材の軸部（先端部）を上板に対して加圧しながら高速で回転させることで上板を貫通し、接続部材の軸部の先端部が下板と接合するとともに、上板が接続部材の頭部と下板との問で固定された接合継手（複合部材）を製造する場合に、下板として本開示に係る摩擦圧接用鋼板を好適に用いることができる。
[Method of manufacturing a joint]
The friction welding steel plate according to the present disclosure is used to manufacture a joint by joining other members by friction welding. The method of manufacturing a joint using the friction welding steel plate according to the present disclosure is not particularly limited, but for example, when manufacturing a joint (composite member) in which an upper plate (first plate material) and a lower plate (second plate material) are overlapped, a connecting member having a head and a shaft such as a rivet is used, and the shaft part (tip part) of the connecting member is rotated at high speed while pressing against the upper plate, penetrating the upper plate, and the tip part of the shaft part of the connecting member is joined to the lower plate, and the upper plate is fixed between the head of the connecting member and the lower plate, the friction welding steel plate according to the present disclosure can be suitably used as the lower plate.
図６は、２枚の板材とリベット状の接続部材を用いて摩擦圧接により接合する方法の一例を示す概略図である。
図６に示す接合継手では、下板２Ｂとして本開示に係る摩擦圧接用鋼板を用いて上板３と下板２Ｂが重ね合わされており、リベット状の接続部材１Ｂが上板３を貫通して下板２Ｂと摩擦圧接により接合されている。上板３は、リベット状の接続部材１Ｂの頭部１２と下板２Ｂとによって挟まれて固定されている。
FIG. 6 is a schematic diagram showing an example of a method for joining two plate materials by friction welding using a rivet-like connecting member.
In the joint shown in Fig. 6, an upper plate 3 and a lower plate 2B are overlapped using the steel plate for friction welding according to the present disclosure as the lower plate 2B, and a rivet-like connecting member 1B penetrates the upper plate 3 and is joined to the lower plate 2B by friction welding. The upper plate 3 is sandwiched and fixed between the head 12 of the rivet-like connecting member 1B and the lower plate 2B.
上板３は、接続部材の軸部１１が貫通して下板２Ｂと摩擦圧接し得るものであれば特に限定されず、例えば、樹脂板、金属板等を用いることができる。金属板としては、例えば、アルミニウム板、アルミニウム合金板等の軽金属板、鋼板等が挙げられる。
なお、上板３は、接続部材１Ｂの軸部１１が貫通する予定の箇所に、貫通孔３１Ｂを有していてもよい。
また、上板３として、同種又は異種の板材を複数枚重ね合わせて用いてもよい。すなわち、上板３と下板２Ｂは、直接重ね合わされていてもよいし、他の板材を介して重ね合わされていてもよい。
The upper plate 3 is not particularly limited as long as the shaft portion 11 of the connection member can penetrate therethrough and be frictionally welded to the lower plate 2B, and may be, for example, a resin plate, a metal plate, etc. Examples of metal plates include light metal plates such as aluminum plates and aluminum alloy plates, and steel plates.
The upper plate 3 may have a through hole 31B at a location where the shaft portion 11 of the connection member 1B is to pass through.
Furthermore, a plurality of plates of the same or different types may be stacked together to form the upper plate 3. That is, the upper plate 3 and the lower plate 2B may be stacked directly on each other, or may be stacked on each other via another plate material.
このような多種多様の上板３を含むものであっても、下板２Ｂとして本開示に係る摩擦圧接用鋼板を用いて接合継手１０Ｂを製造することで、接続部材１Ｂと下板２Ｂとの摩擦圧接部（接合部）の継手強度が優れた接合継手１０Ｂが得られる。 Even if the joint includes such a wide variety of upper plates 3, by manufacturing the joint 10B using the friction welding steel plate according to the present disclosure as the lower plate 2B, a joint 10B having excellent joint strength at the friction welded portion (joint) between the connection member 1B and the lower plate 2B can be obtained.
上板３として鋼板を用いる場合は、接続部材１Ｂと下板２Ｂとの摩擦圧接をより確実に行わせるために、下板２Ｂとなる本開示に係る摩擦圧接用鋼板よりも引張強さが低い鋼板を、上板３として用いることが好ましい。 When a steel plate is used as the upper plate 3, in order to ensure more reliable friction welding between the connection member 1B and the lower plate 2B, it is preferable to use a steel plate as the upper plate 3 that has a lower tensile strength than the friction welding steel plate according to the present disclosure that serves as the lower plate 2B.
上板３及び下板２Ｂは、少なくとも接合対象部分が板状の構造を有していればよく、板材全体が板状の構造を有していなくてもよい。 The upper plate 3 and the lower plate 2B need only have a plate-like structure at least in the portions to be joined, and the entire plate material does not need to have a plate-like structure.
また、接続部材も頭部１２と軸部１１を有するリベット状に限定されない。
図７は、２枚の板材と棒状の接続部材を用いて摩擦圧接により接合する方法の他の例を示す概略図である。図７に示す実施形態では、接合継手１０Ａは、円柱状又は多角柱状の軸部を有する棒状の接続部材が使用されている。かかる接合継手１０Ａは、下板２Ｂである本開示に係る摩擦圧接用鋼板の上面に上板３が重ね合わされて、その上方側（摩擦圧接用鋼板とは反対側）から棒状の接続部材１が上板３を貫通して、接続部材１の下方側先端部（底面）と下板２Ｂとが摩擦圧接により接合されている。
このような接続部材１を用いて摩擦圧接を行った場合、接続部材１の上板３から突出する部分を上方側から専用工具で叩いてかしめることで、接続部材１のかしめ部と下板２Ｂとの問で上板３を固定することができる。
Furthermore, the connecting member is not limited to a rivet-like member having a head portion 12 and a shaft portion 11 .
7 is a schematic diagram showing another example of a method for joining two plates by friction welding using a rod-shaped connecting member. In the embodiment shown in FIG. 7, a rod-shaped connecting member having a cylindrical or polygonal prism-shaped shaft is used as the joint 10A. In the joint 10A, an upper plate 3 is superimposed on the upper surface of the steel plate for friction welding according to the present disclosure, which is a lower plate 2B, and a rod-shaped connecting member 1 penetrates the upper plate 3 from the upper side (opposite the steel plate for friction welding), and the lower tip (bottom surface) of the connecting member 1 and the lower plate 2B are joined by friction welding.
When friction welding is performed using such a connecting member 1, the part of the connecting member 1 protruding from the upper plate 3 can be struck from above with a special tool to crimp the upper plate 3, thereby fixing the upper plate 3 between the crimped portion of the connecting member 1 and the lower plate 2B.
上板と下板とを重ねわせた積層体に対して、接続部材を回転させながら押圧する際の加圧力Ｆ（ｋＮ）及び回転数は、接続部材の軸部が上板を貫通し、下板と摩擦圧接できれば特に限定されず、例えば５ｋＮ以上の加圧力で、１０００ｒｐｍ８０００ｒｐｍの回転数が挙げられる。 The pressure F (kN) and rotation speed when the connecting member is rotated and pressed against the laminate consisting of the upper and lower plates are not particularly limited as long as the shaft of the connecting member penetrates the upper plate and can be frictionally welded to the lower plate. For example, a pressure of 5 kN or more and a rotation speed of 1000 rpm to 8000 rpm can be used.
本開示に係る摩擦圧接用鋼板と他の部材とを摩擦圧接によって接合することで、優れた継手強度を有する接合継手を得ることができる。そのため、本開示に係る摩擦圧接用鋼板は、例えば、自動車の車体部品や建築物の構造体など、摩擦圧接を利用した様々な構造部品の製造に適用することが可能である。
例えば、本開示の別の態様に係る自動車用部材は、上述された実施形態に係る接合継手（複合部材）を有する。これにより、継手強度に優れる自動車用部材とすることができる。なお、自動車用部材の種類は特に限定されない。
By joining the steel plate for friction welding according to the present disclosure to other members by friction welding, a joint having excellent joint strength can be obtained. Therefore, the steel plate for friction welding according to the present disclosure can be applied to the manufacture of various structural parts using friction welding, such as, for example, automobile body parts and building structures.
For example, an automobile component according to another aspect of the present disclosure has the joint (composite component) according to the above-described embodiment. This makes it possible to obtain an automobile component having excellent joint strength. The type of the automobile component is not particularly limited.
以下、実施例によって本開示に係る摩擦圧接用鋼板をより具体的に説明する。尚、本開示に係る摩擦圧接用鋼板はこれらの実施例に限定されるものではない。 The steel plate for friction welding according to the present disclosure will be described in more detail below with reference to examples. Note that the steel plate for friction welding according to the present disclosure is not limited to these examples.
［摩擦圧接用鋼板の製造］
表１に示す化学成分を有する材料を実験室にて溶解して鋳込んだインゴットを熱間圧延（加熱温度１２５０℃、圧延温度（仕上げ圧延温度）９００℃のち５００℃まで水冷却、その後空冷）した後、冷間圧延にて厚さ２．０ｍｍとした。
冷間圧延後に熱処理を行った。ここで熱処理は９００℃まで１５℃／ｓｅｃで加熱し、その後、表２に示す熱処理パターンＡ～Ｉのいずれかを選択した。
表１に示す化学成分（鋼成分）Ｎｏ．１～４９と表２に示す熱処理パターンＡ～Ｉの組み合わせを変更することで摩擦圧接用鋼板Ｎｏ．１～８０を製造した。なお、表１に示す成分以外の残部はＦｅ及び不純物である。各表における下線は本開示の範囲から外れることを意味する。
[Manufacturing of steel plates for friction welding]
Materials having the chemical compositions shown in Table 1 were melted in a laboratory and cast into ingots. The ingots were hot rolled (heating temperature 1250°C, rolling temperature (finish rolling temperature) 900°C, then water cooled to 500°C, and then air cooled), and then cold rolled to a thickness of 2.0 mm.
After cold rolling, the steel was subjected to heat treatment by heating to 900° C. at 15° C./sec, and then one of the heat treatment patterns A to I shown in Table 2 was selected.
Steel plates for friction welding Nos. 1 to 80 were manufactured by changing the combination of chemical components (steel components) Nos. 1 to 49 shown in Table 1 and heat treatment patterns A to I shown in Table 2. The balance other than the components shown in Table 1 is Fe and impurities. The underlines in each table mean that they are outside the scope of the present disclosure.
［鋼板の引張強さの測定］
得られた鋼板に対して、ＪＩＳ５号の引張試験片を作製してＪＩＳ Ｚ ２２４１：２０１１に準拠して引張試験を行い、引張強さを測定した。
[Measurement of tensile strength of steel plate]
JIS No. 5 tensile test pieces were prepared from the obtained steel plates, and tensile tests were performed in accordance with JIS Z 2241:2011 to measure the tensile strength.
［摩擦圧接］
１０００ＭＰａ級の銅製の丸棒（直径４．５ｍｍ、長さ７ｍｍ）を用い、上記の得られた鋼板Ｎｏ．１～７９に対してそれぞれ摩擦圧接を行って接合継手を製造した。摩擦圧接は、上記にて作製した鋼板に加圧力７ｋＮ、回転数５０００ｒｐｍにて実施した。加圧時間は１．５ｓとした。
[Friction welding]
A 1000 MPa class copper round bar (diameter 4.5 mm, length 7 mm) was used to friction weld each of the steel plates No. 1 to 79 obtained above to produce a welded joint. The friction welding was performed on the steel plates prepared above at a pressure of 7 kN and a rotation speed of 5000 rpm. The pressure application time was 1.5 s.
［評価］
上記摩擦圧接により得られた接合継手の継手強度を測定した。接合継手の継手強度は、摩擦圧接により鋼板に接合した丸棒を鋼板から垂直方向に引張り、接合部を破断させた際の最大荷重を測定した。継手強度は５．０ｋＮ以上のものを継手強度が高く、合格レベルと判断した。
また、鋼板の引張試験において、引張強さが７８０ＭＰａを下回るものを強度不足と判断した。また、鋼板製造中に破断や次工程での試験ができないものなどは製造困難と判断した。
結果を表３－１及び表３－２に示す。なお、鋼板組織の各分率は前述した方法によって測定を行い、マルテンサイト、焼戻しマルテンサイト、ラス状ベイナイト、及び焼戻しラス状ベイナイトの「合計分率」が１００％に満たない場合の残部組織は、フェライト、残留オーステナイト、及びパーライトのいずれか１種又は２種以上であった。
[evaluation]
The joint strength of the joint obtained by the above friction welding was measured. The joint strength of the joint was measured by pulling a round bar joined to a steel plate by friction welding in a direction perpendicular to the steel plate, and measuring the maximum load at which the joint broke. A joint strength of 5.0 kN or more was determined to be high and at an acceptable level.
In the tensile tests of steel plates, those with a tensile strength below 780 MPa were judged to have insufficient strength. Steel plates that broke during production or could not be tested in the next process were judged to be difficult to manufacture.
The results are shown in Tables 3-1 and 3-2. The fractions of the steel sheet structures were measured by the method described above, and when the "total fraction" of martensite, tempered martensite, lath bainite, and tempered lath bainite was less than 100%, the remaining structure was one or more of ferrite, retained austenite, and pearlite.
本開示における鋼成分を有し、マルテンサイト、焼戻しマルテンサイト、ラス状ベイナイト及び焼戻しラス状ベイナイトの合計分率が６０％以上の鋼組織を有する鋼板を用いた接合継手は、５．０ｋＮを超える高い継手強度が得られている。
対して、鋼板の鋼成分に関わらず、マルテンサイト、焼戻しマルテンサイト、ラス状ベイナイト及び焼戻しラス状ベイナイトの合計分率が６０％を下回る鋼板を用いた接合継手では、継手強度は５．０ｋＮに満たない。
A bonded joint using a steel plate having the steel composition according to the present disclosure and having a steel structure in which the total fraction of martensite, tempered martensite, lath bainite and tempered lath bainite is 60% or more has a high joint strength of more than 5.0 kN.
In contrast, regardless of the steel composition of the steel plate, in a joint using a steel plate in which the total fraction of martensite, tempered martensite, lath bainite and tempered lath bainite is less than 60%, the joint strength is less than 5.0 kN.
３、１０ 上板
２Ｂ、２０ 下板
１Ｂ、１、３０ 接続部材
１０Ａ、１０Ｂ 接合継手
１１、３４ 軸部
１２、３２ 頭部
３１Ｂ 貫通孔
ＰＢ、４０ 接合部
3, 10 Upper plate 2B, 20 Lower plate 1B, 1, 30 Connection member 10A, 10B Joint joint 11, 34 Shaft portion 12, 32 Head portion 31B Through hole P B , 40 Joint portion
Claims (9)
Ｃ：０．１０～０．７０％、
Ｓｉ：０．１０～３．５０％、
Ｍｎ：０．５０～５．００％、
Ｐ：０．０２０％以下、
Ｓ：０．０５０％以下、
Ａｌ：３．０００％以下、及び
Ｎ：０．０１０％以下であり、
残部が、Ｆｅ及び不純物からなる鋼成分を有し、
マルテンサイト、焼戻しマルテンサイト、ラス状ベイナイト、及び焼戻しラス状ベイナイトからなる群より選ばれる１種又は２種以上の組織を含み、前記組織の合計分率が６０％以上である鋼組織を有し、
引張強さが７８０ＭＰａ以上である、
摩擦圧接用鋼板。 In mass percent,
C: 0.10 to 0.70%,
Si: 0.10 to 3.50%,
Mn: 0.50 to 5.00%,
P: 0.020% or less,
S: 0.050% or less,
Al: 3.000% or less, and N: 0.010% or less;
The balance has a steel composition consisting of Fe and impurities,
The steel has a steel structure including one or more structures selected from the group consisting of martensite, tempered martensite, lath bainite, and tempered lath bainite, the total fraction of the structures being 60% or more;
The tensile strength is 780 MPa or more.
Steel plate for friction welding.
Ｔｉ：０．３０％以下、
Ｎｂ：０．３０％以下、及び、
Ｖ：０．３０％以下
からなる群より選ばれる１種又は２種以上を含む請求項１に記載の摩擦圧接用鋼板。 Instead of a part of the Fe, in mass%,
Ti: 0.30% or less,
Nb: 0.30% or less; and
The steel plate for friction welding according to claim 1, further comprising one or more elements selected from the group consisting of: V: 0.30% or less.
前記Ｆｅの一部に代えて、質量％で、
Ｃｒ：５．０％以下、及び、Ｍｏ：２．０％以下の１種又は２種を含む請求項１又は請求項２に記載の摩擦圧接用鋼板。 The N: 0.005% or less,
Instead of a part of the Fe, in mass%,
3. The steel plate for friction welding according to claim 1 or 2, comprising one or both of Cr: 5.0% or less and Mo: 2.0% or less.
Ｃａ：０．００３％以下、
ＲＥＭ：０．０５％以下、
Ｍｇ：０．０５０％以下、及び
Ｚｒ：０．０５０％以下
からなる群より選ばれる１種又は２種以上を含む請求項１～請求項５のいずれか１項に記載の摩擦圧接用鋼板。 Instead of a part of the Fe, in mass%,
Ca: 0.003% or less,
REM: 0.05% or less,
The steel plate for friction welding according to any one of claims 1 to 5, further comprising one or more selected from the group consisting of Mg: 0.050% or less, and Zr: 0.050% or less.
請求項１～請求項７のいずれか１項に記載の摩擦圧接用鋼板であって、前記第１の板材に重ね合わされた第２の板材と、
頭部及び軸部を有し、前記第１の板材と前記第２の板材とを接続する接続部材と、
を含み、
前記接続部材の前記軸部が前記第１の板材を貫通して前記軸部の先端部が前記第２の板材と接合されており、前記第１の板材が前記接続部材の前記頭部と前記第２の板材との間で固定された構造を有する、
複合部材。 A first plate material;
The steel plate for friction welding according to any one of claims 1 to 7, comprising: a second plate material overlapped on the first plate material;
a connecting member having a head portion and a shaft portion, the connecting member connecting the first plate material and the second plate material;
Including,
The shaft portion of the connection member penetrates the first plate material, and a tip portion of the shaft portion is joined to the second plate material, and the first plate material has a structure in which the head portion of the connection member and the second plate material are fixed.
Composite material.
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| US20180274052A1 (en) | 2017-03-21 | 2018-09-27 | Ford Global Technologies, Llc | Rapid local annealing of high strength steel |
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| JP2004018993A (en) | 2002-06-20 | 2004-01-22 | Aichi Steel Works Ltd | Low alloy non-heat-treated heat resistant steel having reduced variation in strength under high temperature environment and method of producing the same |
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| JP2008255369A (en) | 2007-03-30 | 2008-10-23 | Jfe Steel Kk | High-strength, high-workability hot rolled steel sheet having excellent workability in friction stir welding process, and its manufacturing method |
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