JP2016128173A - Resistance spot welding method - Google Patents

Resistance spot welding method Download PDF

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JP2016128173A
JP2016128173A JP2015002748A JP2015002748A JP2016128173A JP 2016128173 A JP2016128173 A JP 2016128173A JP 2015002748 A JP2015002748 A JP 2015002748A JP 2015002748 A JP2015002748 A JP 2015002748A JP 2016128173 A JP2016128173 A JP 2016128173A
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plate
spot welding
resistance spot
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welding method
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JP6428272B2 (en
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ひとみ 西畑
Hitomi Nishihata
ひとみ 西畑
泰山 正則
Masanori Taiyama
正則 泰山
康信 宮崎
Yasunobu Miyazaki
康信 宮崎
仁寿 徳永
Jinju Tokunaga
仁寿 徳永
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Nippon Steel Corp
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Nippon Steel and Sumitomo Metal Corp
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Abstract

PROBLEM TO BE SOLVED: To provide a resistance spot welding method which can perform spot welding regardless of a combination of materials, and can obtain sufficient joint characteristics.SOLUTION: A spot welding method includes: a preparation step of preparing a plate set including a lamination part 10 in which plate materials 1, 2, 3 are stacked in three layers; and a welding step of sandwiching the lamination part 10 of the plate set with a pair of electrodes 20, 20, applying a current between the electrodes 20, 20 while applying pressure to the lamination part 10 with the electrodes 20, 20, and applying resistance spot welding to the lamination part 10. In the preparation step, as the lamination part 10, the plate materials 1, 3 made of the same type of metal are arranged at outermost layers, and the plate material 2, which is made of the same material as either one of the plate materials 1, 3 of the outermost layers and has a through hole 2a, is arranged at an inner layer. In the welding step, the resistance spot welding is applied while the position of the through hole 2a of the plate material 2 of the inner layer and the position of the electrodes 20, 20 are matched.SELECTED DRAWING: Figure 1B

Description

本発明は、板材同士を接合するための抵抗スポット溶接方法に関する。   The present invention relates to a resistance spot welding method for joining plate materials together.

自動車を始めとする輸送機器、産業機器等は、複数の構造部品で構成される。多くの場合、構造部品の製造には、抵抗スポット溶接(以下、単に「スポット溶接」ともいう)が用いられる。   Transportation equipment such as automobiles, industrial equipment, and the like are composed of a plurality of structural parts. In many cases, resistance spot welding (hereinafter, also simply referred to as “spot welding”) is used to manufacture structural parts.

通常、スポット溶接は、以下のとおりに行われる。素材として板組を準備する。板組は、複数の金属の板材が積み重ねられた積層部を有する。次に、一対の電極によって板組の積層部を挟み込む。そして、その電極によって積層部を加圧しながら、電極間に電流を印加する。これにより、板組の積層部は、電極による加圧に伴って隣接する金属板同士が接触し、この接触領域に電流が流れる。その接触領域は電気抵抗による発熱により溶融し、これが凝固してナゲットが形成される。ナゲットの形成により、板組の金属板同士が接合されて繋ぎ合わされ、構造部品が製造される。   Usually, spot welding is performed as follows. Prepare a board as a material. The plate assembly has a stacked portion in which a plurality of metal plate materials are stacked. Next, the laminated portion of the plate assembly is sandwiched between the pair of electrodes. And an electric current is applied between electrodes, pressing the laminated part with the electrode. Thereby, the metal plate which adjoins the lamination | stacking part of a board assembly with the pressurization by an electrode, and an electric current flows into this contact area | region. The contact area is melted by heat generated by electric resistance, and this is solidified to form a nugget. By forming the nugget, the metal plates of the plate set are joined and joined together, and a structural component is manufactured.

近年、輸送機器において、車体の軽量化が推進され、車体を構成する構造部品の軽量化が強く求められている。このため、使用される鋼板の高強度化が進んでいる。一方、鋼板材料の開発においても、環境調和型の次世代材料として、レアメタルを低減した中高炭素鋼の利用が検討されている。この中高炭素鋼は、レアメタルを低減する代わりにC(炭素)を積極的に含有し、材料強度を確保したものである。   In recent years, in transportation equipment, the weight reduction of vehicle bodies has been promoted, and the weight reduction of structural parts constituting the vehicle bodies has been strongly demanded. For this reason, the strengthening of the steel plate used is progressing. On the other hand, in the development of steel plate materials, the use of medium and high carbon steel with reduced rare metals is being considered as an environmentally friendly next-generation material. This medium and high carbon steel positively contains C (carbon) instead of reducing rare metals and ensures material strength.

一般に、鋼板材料は、強度が高まるほど多くの元素を含有した組成となる。しかしながら、鋼板に含まれるC量が多すぎると、焼入れ性が向上し、焼入れ後の組織(マルテンサイト)の硬さも上昇する。このため、中高炭素鋼の溶接の場合、高温からの急速冷却により、硬さの上昇が著しく、溶接金属が脆くなって界面で脆性破断し易くなり、溶接継手の特性が低下する。ここでいう継手特性とは、破断形態、引張せん断強さ(Tensile Shear Strength:TSS)、十字引張強さ(Cross Tensile Strength:CTS)等である。   In general, the steel sheet material has a composition containing more elements as the strength increases. However, when the amount of C contained in the steel plate is too large, the hardenability is improved and the hardness of the structure (martensite) after quenching is also increased. For this reason, in the case of welding of medium and high carbon steels, the rapid increase in hardness due to rapid cooling from a high temperature causes the weld metal to become brittle, making the weld metal brittle and susceptible to brittle fracture at the interface, which degrades the properties of the welded joint. The joint characteristics referred to here include a fracture mode, tensile shear strength (TSS), cross tensile strength (CTS), and the like.

一方、各種ステンレス鋼、TWIP(双晶誘起塑性:TWinning-Induced Plasticity)鋼等のように、Cr、Ni、Mnなどの特定の元素を数%〜数十%含有した高合金鋼に関しては、同一材料同士の共材溶接では継手特性の低下は問題とならない。しかし、高合金鋼と同種の高合金鋼又は低合金鋼とを溶接した場合、溶接金属の著しい硬化が発現し、これに伴って継手特性の低下が問題となることがある。これらの高合金鋼は、特定の組成により室温では安定化した鉄の高温相が存在しているが、同種の鋼と溶け合って溶接金属の組成が変化すると、冷却後に硬くて脆いマルテンサイト組織が出現するためである。   On the other hand, the same is true for high alloy steels containing several% to several tens of% of specific elements such as Cr, Ni, and Mn, such as various stainless steels and TWIP (Twinning-Induced Plasticity) steels. In joint welding of materials, deterioration of joint characteristics is not a problem. However, when high alloy steel and high alloy steel or low alloy steel of the same type are welded, remarkable hardening of the weld metal is manifested, and as a result, deterioration of joint characteristics may become a problem. These high-alloy steels have a high-temperature phase of iron stabilized at room temperature by a specific composition, but when they are mixed with the same type of steel and the composition of the weld metal changes, a hard and brittle martensite structure is formed after cooling. Because it appears.

また、構造部品には、高C(炭素)含有鋼と高C含有鋼等といったように、同一又は同種の金属材料を組み合わせた構造が採用される場合がある。この場合、複数の同一材料又は同種材料の板材が積層され、スポット溶接によって接合される。   In addition, a structure in which the same or similar metal materials are combined, such as high C (carbon) -containing steel and high C-containing steel, may be used for the structural parts. In this case, a plurality of plate materials of the same material or the same material are laminated and joined by spot welding.

同一材料又は同種材料を組み合わせてスポット溶接により接合する場合、下記の問題がある。溶接金属が著しく硬化して脆くなり、十分な継手特性が得られないことがある。この傾向は、特に、高C含有鋼同士のスポット溶接で顕在化する。また、将来的には、Cを更に多く含有する鋼材のスポット溶接が必要になると予想される。その場合は、溶接金属の硬化に伴う脆弱な組織の生成が促進し、継手特性の低下が一層顕在化する。   When joining the same material or the same kind of material by spot welding, there are the following problems. The weld metal may harden and become brittle, and sufficient joint characteristics may not be obtained. This tendency is manifested particularly by spot welding between high C steels. In the future, it is expected that spot welding of a steel material containing more C will be required. In that case, the formation of a fragile structure accompanying the hardening of the weld metal is promoted, and the deterioration of the joint characteristics becomes more obvious.

特開2002−103054号公報(特許文献1)及び特開2013−78782号公報(特許文献2)は、高強度鋼、すなわちややC含有が多く溶接金属が硬化し易い鋼をスポット溶接によって接合する技術を開示する。これらの特許文献1及び2に開示されるスポット溶接方法では、鋼板を積層して電極によって挟み込み、電極間に電流を印加して溶融及び凝固による溶接を行った後、更に電極間への電流印加を追加する。このような溶接後の追加の通電は、後通電と称される。後通電の印加電流は、溶接時の印加電流よりも低い電流、又は短い印加時間での電流であり、鋼板が溶融には至らず発熱する程度の電流である。この後通電により、継手に剥離荷重が負荷されたときの応力集中部であるナゲット端部において、硬化組織が軟化し、Pなどの偏析が低減する。その結果、溶接金属の組織が改善し、継手が破壊する際の抵抗が高まる。   JP 2002-103054 A (Patent Document 1) and JP 2013-78782 A (Patent Document 2) join high strength steel, that is, steel which has a little C content and is easy to harden a weld metal by spot welding. Disclose technology. In the spot welding methods disclosed in these Patent Documents 1 and 2, steel plates are stacked and sandwiched between electrodes, current is applied between the electrodes, welding is performed by melting and solidification, and then current is applied between the electrodes. Add Such additional energization after welding is referred to as post-energization. The applied current for the post-energization is a current lower than the applied current at the time of welding or a current with a short application time, and is a current that can generate heat without causing the steel sheet to melt. By subsequent energization, the hardened structure is softened and segregation such as P is reduced at the nugget end portion, which is a stress concentration portion when a peeling load is applied to the joint. As a result, the structure of the weld metal is improved, and the resistance when the joint is broken increases.

特開2002−103054号公報JP 2002-103054 A 特開2013−78782号公報JP 2013-78782 A

特許文献1及び2に開示されるスポット溶接方法は、いずれもC含有量が0.3質量%程度までである鋼板同士の溶接を対象とする。このため、ナゲット端部、すなわち溶接金属のごく一部で組織が改善し、これにより継手特性の改善が図られる。しかし、より多くのCを含有した鋼板では、ナゲット全体にわたり組織を改善することが必要である。このため、後通電のような短時間かつ局所的な熱処理では、継手特性の改善効果は小さい。   The spot welding methods disclosed in Patent Documents 1 and 2 are all intended to weld steel plates having a C content of up to about 0.3% by mass. For this reason, the structure is improved at the nugget end, that is, only a part of the weld metal, and thereby the joint characteristics are improved. However, in steel sheets containing more C, it is necessary to improve the structure throughout the nugget. For this reason, the effect of improving joint characteristics is small in a short time and local heat treatment such as post-energization.

更に、ステンレス鋼、TWIP鋼等のような高合金鋼の溶接において、同種の高合金鋼又は低合金鋼との溶接で溶接金属の組成が変化した場合、後通電のような熱処理が施されても、もはや鉄の高温相が室温で安定化することはできない。このため、継手特性の改善効果が得られない。   Furthermore, in the welding of high alloy steels such as stainless steel and TWIP steel, if the composition of the weld metal changes due to welding with the same kind of high alloy steel or low alloy steel, a heat treatment such as post-energization is applied. However, the high temperature phase of iron can no longer be stabilized at room temperature. For this reason, the effect of improving joint characteristics cannot be obtained.

本発明の目的は、次の特性を有する抵抗スポット溶接方法を提供することである:
・材料の組み合わせを問わず、スポット溶接を行えること;
・十分な継手特性が得られること。
The object of the present invention is to provide a resistance spot welding method having the following characteristics:
・ Spot welding is possible regardless of the combination of materials;
-Sufficient joint characteristics can be obtained.

本発明の一実施形態による抵抗スポット溶接方法は、
板材同士を接合するためのスポット溶接方法であって、
少なくとも3層に板材が積み重ねられた積層部を含む板組を準備する準備工程と、
前記板組の前記積層部を一対の電極によって挟み込み、前記積層部を前記電極によって加圧しながら前記電極間に電流を印加して、前記積層部に抵抗スポット溶接を施す溶接工程と、を含む。
前記準備工程では、前記積層部として、最外層に互いに同種の金属の板材を配置するとともに、内層に前記最外層の板材のうちのいずれか一方の板材の材料と同一の材料の板材であって貫通穴を有する板材を配置する。
前記溶接工程では、前記内層の板材における前記貫通穴の位置と前記電極の位置を一致させた状態で抵抗スポット溶接を施す。
A resistance spot welding method according to an embodiment of the present invention includes:
A spot welding method for joining plate materials,
A preparation step of preparing a plate assembly including a laminated portion in which plate materials are stacked in at least three layers;
A welding step of sandwiching the laminated portion of the plate assembly between a pair of electrodes, applying a current between the electrodes while pressing the laminated portion with the electrodes, and performing resistance spot welding on the laminated portion.
In the preparation step, as the laminated portion, the same kind of metal plate material is disposed in the outermost layer, and the inner layer is a plate material of the same material as the material of any one of the outermost layer plate materials, A plate member having a through hole is disposed.
In the welding step, resistance spot welding is performed in a state where the position of the through hole and the position of the electrode in the inner layer plate material are matched.

このスポット溶接方法の場合、前記最外層の板材のうちのいずれか一方の板材の材料が高C含有鋼であり、他方の板材の材料が低C含有鋼である構成とすることができる。   In the case of this spot welding method, the material of any one of the outermost plate materials may be a high C content steel, and the material of the other plate material may be a low C content steel.

上記のスポット溶接方法は、下記の構成に変更することができる:
前記最外層の板材の材料が互いに同一であり、
前記内層の板材の材料が前記最外層の板材の材料と同種である。
The above spot welding method can be modified to the following configuration:
The material of the outermost plate material is the same,
The material of the inner layer plate is the same as the material of the outermost plate.

このスポット溶接方法の場合、前記最外層の板材の材料が低C含有鋼であり、前記内層の板材の材料が高C含有鋼である構成とすることができる。この構成に代えて、前記最外層の板材の材料が高合金鋼である構成とすることができる。   In the case of this spot welding method, the plate material of the outermost layer may be a low C content steel, and the material of the plate material of the inner layer may be a high C content steel. Instead of this configuration, the outermost plate material may be a high alloy steel.

上記のスポット溶接方法は、下記の構成に変更することができる:
前記最外層の板材の材料が互いに同種であり、
前記内層の板材の材料が前記最外層の板材の材料と同種である。
The above spot welding method can be modified to the following configuration:
The material of the outermost plate material is the same as each other,
The material of the inner layer plate is the same as the material of the outermost plate.

上記のいずれのスポット溶接方法も、前記内層の板材が絶縁被膜を有する構成とすることができる。   In any of the above spot welding methods, the plate material of the inner layer may have an insulating coating.

上記のいずれのスポット溶接方法も、前記最外層の板材のうちのいずれか一方の板材が当て板である構成とすることができる。   Any of the above spot welding methods may have a configuration in which any one of the outermost plate members is a contact plate.

上記のいずれのスポット溶接方法も、前記内層の板材における前記貫通穴の輪郭形状が円形又は正方形であり、前記貫通穴の直径又は一辺の長さが目標のナゲット径よりも大きいことが好ましい。   In any of the above spot welding methods, it is preferable that a contour shape of the through hole in the plate material of the inner layer is a circle or a square, and the diameter or the length of one side of the through hole is larger than a target nugget diameter.

上記のいずれのスポット溶接方法も、前記最外層の板材の各厚みが3.0mm以下であり、前記内層の板材の全体の厚みが2.4mm以下であることが好ましい。   In any of the above spot welding methods, it is preferable that the thickness of the outermost layer plate material is 3.0 mm or less, and the total thickness of the inner layer plate material is 2.4 mm or less.

本発明の抵抗スポット溶接方法は、下記の顕著な効果を有する:
・材料の組み合わせを問わず、スポット溶接を行えること;
・十分な継手特性が得られること。
The resistance spot welding method of the present invention has the following significant effects:
・ Spot welding is possible regardless of the combination of materials;
-Sufficient joint characteristics can be obtained.

図1Aは、本実施形態の抵抗スポット溶接方法の手順を模式的に示す断面図であり、積み重ねられる前の板材を示す。FIG. 1A is a cross-sectional view schematically showing a procedure of the resistance spot welding method of the present embodiment, and shows a plate material before being stacked. 図1Bは、本実施形態の抵抗スポット溶接方法の手順を模式的に示す断面図であり、板材が積み重ねられた積層部についての溶接前の状態を示す。FIG. 1B is a cross-sectional view schematically showing a procedure of the resistance spot welding method of the present embodiment, and shows a state before welding of a laminated portion in which plate materials are stacked. 図1Cは、本実施形態の抵抗スポット溶接方法の手順を模式的に示す断面図であり、溶接中期の状態を示す。FIG. 1C is a cross-sectional view schematically showing the procedure of the resistance spot welding method of the present embodiment, and shows a state in the middle of welding. 図1Dは、本実施形態の抵抗スポット溶接方法の手順を模式的に示す断面図であり、溶接終期の状態を示す。FIG. 1D is a cross-sectional view schematically showing the procedure of the resistance spot welding method of the present embodiment, and shows a state at the end of welding. 図1Eは、本実施形態の抵抗スポット溶接方法の手順を模式的に示す断面図であり、溶接完了後の積層部を示す。FIG. 1E is a cross-sectional view schematically showing a procedure of the resistance spot welding method of the present embodiment, and shows a laminated portion after welding is completed.

本発明の一実施形態によるスポット溶接方法は、板材同士を接合するために用いられ、準備工程と、溶接工程と、を含む。準備工程は、少なくとも3層に板材が積み重ねられた積層部を含む板組を準備する工程である。溶接工程は、板組の積層部を一対の電極によって挟み込み、積層部を電極によって加圧しながら電極間に電流を印加して、積層部に抵抗スポット溶接を施す工程である。準備工程では、板組の積層部として、最外層に互いに同一又は同種の金属の板材を配置するとともに、内層に貫通穴を有する板材を配置する。溶接工程では、内層の板材における貫通穴の位置と電極の位置を一致させた状態で抵抗スポット溶接を施す。   The spot welding method by one Embodiment of this invention is used in order to join plate materials, and includes a preparation process and a welding process. The preparation step is a step of preparing a plate set including a laminated portion in which plate materials are stacked in at least three layers. The welding step is a step of performing resistance spot welding on the laminated portion by sandwiching the laminated portion of the plate assembly with a pair of electrodes and applying a current between the electrodes while pressing the laminated portion with the electrodes. In the preparation step, the same or the same type of metal plate material is arranged in the outermost layer as the laminated portion of the plate assembly, and the plate material having a through hole is arranged in the inner layer. In the welding process, resistance spot welding is performed in a state in which the positions of the through holes and the positions of the electrodes in the inner layer plate material are matched.

以下に、本実施形態による抵抗スポット溶接方法について、具体的な態様を説明する。   Below, a specific aspect is demonstrated about the resistance spot welding method by this embodiment.

図1A〜図1Eは、本実施形態の抵抗スポット溶接方法の手順を模式的に示す断面図である。これらの図中、図1Aは、積み重ねられる前の板材を示す。図1Bは、板材が積み重ねられた積層部についての溶接前の状態を示す。図1Cは、溶接中期の状態を示す。図1Dは、溶接終期の状態を示す。図1Eは、溶接完了後の積層部を示す。   1A to 1E are cross-sectional views schematically showing the procedure of the resistance spot welding method of the present embodiment. In these drawings, FIG. 1A shows a plate material before being stacked. FIG. 1B shows a state before welding of the laminated portion in which the plate materials are stacked. FIG. 1C shows a state in the middle of welding. FIG. 1D shows a state at the end of welding. FIG. 1E shows the laminated portion after welding is completed.

本実施形態では、少なくとも3層に板材を組み合わせ、これらの板材をスポット溶接により接合する場合を対象とする。特に、最外層に互いに同種の金属の板材を配置するとともに、内層に最外層のうちのいずれか一方の板材の材料と同一の材料の板材を配置した場合を対象とする。以下では、先ず、最外層の板材として、強度の高い高C含有鋼の板材と、強度の低い低C含有鋼の板材を配置し、内層の板材として、強度の高い高C含有鋼の板材を配置した場合を例示する。   In this embodiment, the case where a plate material is combined with at least three layers and these plate materials are joined by spot welding is targeted. In particular, the case where the same kind of metal plate material is disposed in the outermost layer and the same material as the material of any one of the outermost layers is disposed in the inner layer is targeted. In the following, first, as a plate material of the outermost layer, a plate material of a high C content steel having a high strength and a plate material of a low C content steel having a low strength are arranged. The case where it arrange | positions is illustrated.

ここで、同種の金属材料とは、化学組成において最も含有量の多い元素が同一である金属材料を意味する。例えば、高C含有鋼と低C含有鋼は同種である。同一の金属材料とは、化学組成が厳密に同一である金属材料のみならず、規格上の呼び名が同一である金属材料を意味する。高C含有鋼は、C含有量が0.4質量%以上のものをいう。低C含有鋼は、C含有量が0.4質量%未満のものをいう。   Here, the same kind of metal material means a metal material having the same element with the highest content in the chemical composition. For example, high C content steel and low C content steel are the same type. The same metal material means not only a metal material having the same chemical composition but also a metal material having the same name in the standard. High C content steel means C content of 0.4 mass% or more. Low C-containing steel refers to steel having a C content of less than 0.4 mass%.

素材として板組を準備する。図1A及び図1Bに示すように、板組は、3枚の板材1、2、3から構成され、これらの板材1、2、3が順に積み重ねられた3層構造の積層部10を含む。この積層部10において、最外層である第1層及び第3層の板材1、3のうち、第1層の板材1の材料は高C含有鋼である。第3層の板材3の材料は、第1層の板材1の材料と同種の低C含有鋼である。内層である第2層の板材2の材料は、第1層の板材1の材料と同一の高C含有鋼である。   Prepare a board as a material. As shown in FIGS. 1A and 1B, the plate assembly includes three plate members 1, 2, and 3, and includes a laminated portion 10 having a three-layer structure in which these plate members 1, 2, and 3 are sequentially stacked. In this laminated part 10, the material of the 1st layer board | plate material 1 is the high C content steel among the board | plate materials 1 and 3 of the 1st layer and 3rd layer which are outermost layers. The material of the plate material 3 of the third layer is the same kind of low C content steel as the material of the plate material 1 of the first layer. The material of the plate material 2 of the second layer as the inner layer is the same high C content steel as the material of the plate material 1 of the first layer.

つまり、高C含有鋼の第2層の板材2が、高C含有鋼の第1層の板材1と低C含有鋼の第3層の板材3との間に挟み込まれる。第2層の板材2には、予め貫通穴2aが設けられる。この貫通穴2aの輪郭形状は、円形であっても、正方形であってもよい。実用的には、貫通穴2aは円形である。   That is, the plate material 2 of the second layer of high C content steel is sandwiched between the plate material 1 of the first layer of high C content steel and the plate material 3 of the third layer of low C content steel. The second layer plate 2 is provided with a through hole 2a in advance. The outline shape of the through hole 2a may be circular or square. Practically, the through hole 2a is circular.

第1層及び第3層(最外層)の板材1、3のうち、第2層(内層)の板材2と同種であるが同一でなく、低C含有鋼である第3層の板材3は、当て板であり、構造部品の本質的な形状を形成するものではない。すなわち、高C含有鋼の同一材料である第1層の板材1と第2層の板材2が、構造部品の本質的な形状を形成する。準備工程では、このような構成の積層部10を含む板組を準備する。   Of the first layer 3 and the third layer (outermost layer) plate materials 1 and 3, the third layer plate material 3 is the same type as the second layer (inner layer) plate material 2 but is not the same, and is a low C content steel. It is a backing plate and does not form the essential shape of a structural part. That is, the first layer plate 1 and the second layer plate 2 which are the same material of high C content steel form the essential shape of the structural component. In the preparation step, a plate set including the stacked portion 10 having such a configuration is prepared.

準備工程を経た後、スポット溶接による溶接工程に移行する。溶接工程では、先ず、板組の積層部10を一対の電極20、20によって挟み込む。その際、図1Bに示すように、第2層(内層)の板材2に設けられた貫通穴2aの位置と電極20、20の位置を一致させた状態にする。続いて、電極20、20によって積層部10を加圧する。これにより、図1Cに示すように、第1層及び第3層(最外層)の板材1、3が変形し、第2層(内層)の板材2における貫通穴2aの領域で互いに接触した状態になる。   After passing through the preparation process, the process proceeds to a welding process by spot welding. In the welding process, first, the laminated portion 10 of the plate assembly is sandwiched between the pair of electrodes 20 and 20. At that time, as shown in FIG. 1B, the positions of the through holes 2a provided in the plate material 2 of the second layer (inner layer) and the positions of the electrodes 20 and 20 are made to coincide with each other. Subsequently, the stacked portion 10 is pressurized by the electrodes 20 and 20. As a result, as shown in FIG. 1C, the plate materials 1 and 3 of the first layer and the third layer (outermost layer) are deformed and are in contact with each other in the region of the through hole 2a in the plate material 2 of the second layer (inner layer). become.

更に、電極20、20によって積層部10を加圧しながら、電極20、20間に電流を印加する。これにより、第1層及び第3層(最外層)の板材1、3の接触領域に電流が流れる。その接触領域は抵抗発熱により溶融して凝固し、図1Dに示すように、ナゲット4が形成される。ナゲット4の周囲では、接触する第1層及び第3層(最外層)の板材1、3同士が圧接される。   Furthermore, a current is applied between the electrodes 20, 20 while pressing the laminated part 10 with the electrodes 20, 20. Thereby, an electric current flows into the contact area | region of the board | plate materials 1 and 3 of a 1st layer and a 3rd layer (outermost layer). The contact area is melted and solidified by resistance heat generation, and a nugget 4 is formed as shown in FIG. 1D. Around the nugget 4, the first and third layers (outermost layers) of the plate materials 1, 3 are in pressure contact with each other.

また、上記の溶接工程において、第1層及び第3層(最外層)の板材1、3が互いに接触する以前に、電極20、20間に電流を印加するように変更することもできる。この場合、先ず、第1層及び第3層(最外層)の板材1、3は、第2層(内層)の板材2における貫通穴2aの周囲の環状領域で第2層の板材2と接触した状態になる。このため、第1層及び第3層の板材1、3と第2層の板材2との環状接触領域に電流が流れる。これにより、その環状領域が発熱するため、その環状領域内及びその近傍の領域で第1層及び第3層の板材1、3が軟化する。更に、電極20、20間に電流を印加しながら、電極20、20による積層部10の加圧を続けると、軟化した第1層及び第3層(最外層)の板材1、3が変形し、第2層(内層)の板材2における貫通穴2aの領域で互いに接触した状態になる(図1C参照)。これにより、第1層及び第3層(最外層)の板材1、3の接触領域にも電流が流れ、最終的にナゲット4が形成される(図1D参照)。   Further, in the above-described welding process, before the first layer and the third layer (outermost layer) plate members 1 and 3 come into contact with each other, the current can be changed so as to be applied between the electrodes 20 and 20. In this case, first, the plate materials 1 and 3 of the first layer and the third layer (outermost layer) are in contact with the plate material 2 of the second layer in the annular region around the through hole 2a in the plate material 2 of the second layer (inner layer). It will be in the state. For this reason, an electric current flows into the annular contact area of the plate materials 1 and 3 of the first layer and the third layer and the plate material 2 of the second layer. Thereby, since the annular region generates heat, the plate materials 1 and 3 of the first layer and the third layer are softened in and around the annular region. Further, if the pressing of the laminated portion 10 by the electrodes 20 and 20 is continued while applying current between the electrodes 20 and 20, the softened first and third layer (outermost layer) plate materials 1 and 3 are deformed. Then, they are in contact with each other in the region of the through hole 2a in the plate material 2 of the second layer (inner layer) (see FIG. 1C). Thereby, an electric current flows also in the contact area | region of the board | plate materials 1 and 3 of a 1st layer and a 3rd layer (outermost layer), and the nugget 4 is finally formed (refer FIG. 1D).

このようにして積層部10がスポット溶接により接合され、構造部品が製造される(図1E参照)。スポット溶接では、高C含有鋼である第1層(最外層)の板材1と、低C含有鋼である第3層(最外層)の板材3とが、高C含有鋼である第2層(内層)の板材2における貫通穴2aを介して接合される。この接合により、積層部10は、内層の板材2が最外層の板材1、3同士の間で強力に挟み込まれた状態になる。   Thus, the laminated part 10 is joined by spot welding, and a structural component is manufactured (see FIG. 1E). In spot welding, the first layer (outermost layer) plate material 1 that is high C content steel and the third layer (outermost layer) plate material 3 that is low C content steel are the second layer that is high C content steel. It joins through the through-hole 2a in the board | plate material 2 of (inner layer). By this joining, the laminated portion 10 is in a state in which the inner-layer plate material 2 is strongly sandwiched between the outermost plate materials 1 and 3.

このように、本実施形態のスポット溶接方法によれば、高C含有鋼の同一材料同士を組み合わせて接合することができる。また、スポット溶接による実質的な接合は、高C含有鋼と低C含有鋼という同種材料である最外層(第1層及び第3層)の板材1、3同士で行われる。このため、溶接金属のC含有量は、高C含有鋼同士の溶接を行った場合よりも低下する。溶接金属のC含有量は、溶接対象の鋼板それぞれのC含有量に依存し、両者のC含有量のほぼ平均となるからである。したがって、溶接金属の硬化に起因した脆弱な組織の生成に伴う破断が生じないことから、十分な継手特性を得ることができる。   Thus, according to the spot welding method of this embodiment, the same material of high C content steel can be combined and joined. Moreover, the substantial joining by spot welding is performed between the plate materials 1 and 3 of the outermost layers (first layer and third layer), which are the same kind of material, high C content steel and low C content steel. For this reason, C content of a weld metal falls rather than the case where welding of high C content steels is performed. This is because the C content of the weld metal depends on the C content of each of the steel plates to be welded, and is approximately the average of the C content of both. Therefore, since the fracture | rupture accompanying the production | generation of a weak structure resulting from hardening of a weld metal does not arise, sufficient joint characteristics can be acquired.

上記した本実施形態のスポット溶接方法において、最外層(第1層及び第3層)の板材1、3の材料が互いに同種の金属材料であり、内層(第2層)の板材2の材料が最外層の板材1、3のうちのいずれか一方の板材の材料と同一である限り、それらの材料に限定はない。例えば、上記の実施形態において、内層である第2層の板材2の材料を、最外層である第3層の板材3の材料と同一の低C含有鋼とすることができる。   In the spot welding method of this embodiment described above, the materials of the outermost layer (first layer and third layer) of the plate materials 1 and 3 are the same kind of metal materials, and the inner layer (second layer) of the plate material 2 is made of the same material. As long as it is the same as the material of any one of the outermost plate materials 1, 3, there is no limitation on those materials. For example, in the above embodiment, the material of the second layer plate 2 that is the inner layer can be the same low C content steel as the material of the third layer plate 3 that is the outermost layer.

例えば、鋼系材料でいうと、低C含有鋼と、高C含有鋼等は、互いに同種の金属材料である。その他に、α系(フェライト系)ステンレス鋼と、γ系(オーステナイト系)ステンレス鋼と、TWIP(双晶誘起塑性: TWinning-Induced Plasticity)鋼等は、互いに同種の高合金鋼の金属材料である。Al系材料でいうと、Alと、Al合金等は、互いに同種の金属材料である。   For example, in terms of steel materials, low C-containing steel, high C-containing steel, and the like are the same metal materials. In addition, α-based (ferritic) stainless steel, γ-based (austenitic) stainless steel, TWIP (Twinning-Induced Plasticity) steel, etc. are metal materials of the same kind of high alloy steel. . In terms of Al-based materials, Al and Al alloys are the same type of metal materials.

ただし、最外層(第1層及び第3層)の板材1、3の材料が互いに同種の金属材料であり、内層(第2層)の板材2の材料が最外層の板材1、3の材料と同種である構成に変更しても構わない。スポット溶接による実質的な接合が同種の金属材料間で行われるため、接合対象がC含有量又は合金元素含有量の低い金属材料を含んでいれば、溶接金属の硬化が緩和されることに変わりはないからである。   However, the materials of the plate materials 1 and 3 of the outermost layers (first layer and third layer) are the same metal materials, and the material of the plate material 2 of the inner layer (second layer) is the material of the plate materials 1 and 3 of the outermost layer. You may change into the structure which is the same kind as. Since substantial joining by spot welding is performed between the same kind of metal materials, if the object to be joined contains a metal material having a low C content or alloy element content, the hardening of the weld metal is reduced. Because there is no.

例えば、最外層である第1層の板材1、及び内層である第2層の板材2のうち、いずれか一方の板材を高C含有鋼とし、他方の板材をそれとは同種の高C含有鋼とし、別の最外層である第3層の板材3の材料を低C含有鋼とすることができる。第1層の板材1又は第2層の板材2の材料は、めっき鋼板であってもよい。   For example, one of the plate material 1 of the first layer which is the outermost layer and the plate material 2 of the second layer which is the inner layer is a high C content steel, and the other plate material is a high C content steel of the same type. And the material of the plate material 3 of the third layer, which is another outermost layer, can be low C-containing steel. The material of the first layer plate 1 or the second layer plate 2 may be a plated steel plate.

最外層(第1層及び第3層)の板材1、3の材料が互いに同一の金属材料であり、内層(第2層)の板材2の材料が最外層の板材1、3の材料と同種である構成に変更しても構わない。スポット溶接による実質的な接合が同一の金属材料間で行われるため、接合対象がC含有量又は合金元素含有量の低い金属材料を含んでいれば、溶接金属の硬化が緩和されることに変わりはないからである。また、各種ステンレス鋼、TWIP鋼等のような高合金鋼同士の溶接、又はAl合金同士の溶接では、継手特性の低下はないからである。   The materials of the outermost layer (first layer and third layer) plate materials 1 and 3 are the same metal material, and the inner layer (second layer) plate material 2 is the same material as the outermost layer plate materials 1 and 3. You may change into the structure which is. Since substantial joining by spot welding is performed between the same metal materials, if the object to be joined contains a metal material having a low C content or alloy element content, the hardening of the weld metal is reduced. Because there is no. Moreover, it is because there is no deterioration of a joint characteristic in welding of high alloy steels, such as various stainless steels, TWIP steel, etc., or welding of Al alloys.

例えば、最外層である第1層及び第3層の板材1、3を低C含有鋼とし、内層である第2層の板材2を高C含有鋼とすることができる。また、最外層である第1層及び第3層の板材1、3と、内層である第2層の板材2とのうち、いずれか一方の層の板材をα系ステンレス鋼とし、他方の層の板材をγ系ステンレス鋼とすることができる。同様に、最外層の板材1、3と、内層の板材2とのうち、いずれか一方の層の板材をAlとし、他方の層の板材をAl合金とすることができる。   For example, the plate materials 1 and 3 of the first layer and the third layer which are the outermost layers can be made of low C-containing steel, and the plate material 2 of the second layer which is an inner layer can be made of high C-containing steel. Moreover, the board material of any one layer among the board | plate materials 1 and 3 of the 1st layer and 3rd layer which are outermost layers, and the board | plate material 2 of the 2nd layer which is an inner layer is made into alpha system stainless steel, and the other layer The plate material can be γ-based stainless steel. Similarly, the plate material of any one of the plate materials 1 and 3 of the outermost layer and the plate material 2 of the inner layer can be Al, and the plate material of the other layer can be Al alloy.

また、内層(第2層)の板材2は、表面に塗装等の絶縁被膜が施された絶縁被膜付き鋼板(母材:低C含有鋼、高C含有鋼)であっても構わない。スポット溶接による実質的な接合は、金属材料である最外層(第1層及び第3層)の板材1、3同士で行われるため、内層の板材2の特性として導電性は必須でないからである。   Further, the inner layer (second layer) plate 2 may be a steel plate with an insulating coating (base material: low C-containing steel, high C-containing steel) whose surface is coated with an insulating coating such as coating. This is because the substantial joining by spot welding is performed between the outermost layers (first layer and third layer) of the plate materials 1 and 3 which are metal materials, and therefore conductivity is not essential as a characteristic of the inner layer plate material 2. .

下記の表1に、第1層(最外層)の板材1の材料、内層の板材2の材料、及び第3層(最外層)の板材3の材料の組み合わせの一例を示す。   Table 1 below shows an example of a combination of the material of the plate material 1 of the first layer (outermost layer), the material of the plate material 2 of the inner layer, and the material of the plate material 3 of the third layer (outermost layer).

Figure 2016128173
Figure 2016128173

ステンレス鋼、TWIP鋼などの金属材料を組み合わせる場合、最外層(第1層、第3層)の板材1、3としては、それらの同種の金属材料の中でも、互いに同一又は近似する化学組成の金属材料を採用することが好ましい。また、含有量が6質量%を超える合金元素を含む金属材料を組み合わせる場合、最外層(第1層、第3層)の板材1、3としては、その合金元素が共通する金属材料(より好ましくは同一の金属材料)を採用することが好ましい。   When combining metal materials such as stainless steel and TWIP steel, the outermost layer (first layer, third layer) plate materials 1 and 3 have the same or similar chemical composition among the same kind of metal materials. It is preferable to adopt a material. Moreover, when combining the metal material containing the alloy element which content exceeds 6 mass%, as the board | plate materials 1 and 3 of outermost layer (1st layer, 3rd layer), the metal material (more preferably) the alloy element is common. Are preferably the same metal material).

上記した本実施形態のスポット溶接方法において、最外層(第1層及び第3層)の板材1、3のうち、第3層の板材3に代えて第1層の板材1を当て板にしてもよい。もっとも、最外層の板材1、3のうちの一方の板材1、3を必ずしも当て板にする必要はない。すなわち、最外層の板材1、3の両方と内層(第2層)の板材2が構造部品の本質的な形状を形成するものであっても構わない。   In the spot welding method of the present embodiment described above, out of the outermost layer (first layer and third layer) plate members 1 and 3, the first layer plate member 1 is used as the backing plate instead of the third layer plate member 3. Also good. However, it is not always necessary to use one of the outermost plate materials 1 and 3 as the contact plate. That is, both the outermost plate materials 1 and 3 and the inner layer (second layer) plate material 2 may form the essential shape of the structural component.

板組の積層部10は、少なくとも3層に板材が積み重ねられたものであればよい。すなわち、内層が複数枚の板材を積み重ねられた構成でも構わない。この場合、内層の板材の全てに同軸上に貫通穴を設ければよい。   The laminated portion 10 of the plate assembly may be any one in which plate materials are stacked in at least three layers. That is, the inner layer may have a configuration in which a plurality of plate materials are stacked. In this case, a through hole may be provided coaxially in all the inner layer plate materials.

ここで、上記した本実施形態のスポット溶接方法において、最外層(第1層及び第3層)の板材1、3の各厚みは、構造部品の設計仕様に応じて設定される。例えば、最外層の板材1、3の各厚みは、実用的には、0.3mm〜3.0mmである。その厚みが薄過ぎると、強度を確保することができない。このため、その厚みの好ましい下限は、0.3mmであり、より好ましくは0.5mmである。一方、その厚みが厚過ぎると、スポット溶接時に電極からの加圧による変形が困難になり、最外層の板材1、3同士の接触が不十分になる。このため、その厚みの好ましい上限は、3.0mmであり、より好ましくは2.0mmであり、更に好ましくは1.6mmである。   Here, in the above-described spot welding method of the present embodiment, the thicknesses of the plate materials 1 and 3 of the outermost layers (first layer and third layer) are set according to the design specifications of the structural parts. For example, the thicknesses of the outermost plate materials 1 and 3 are practically 0.3 mm to 3.0 mm. If the thickness is too thin, the strength cannot be ensured. For this reason, the minimum with the preferable thickness is 0.3 mm, More preferably, it is 0.5 mm. On the other hand, if the thickness is too thick, deformation by pressurization from the electrodes during spot welding becomes difficult, and contact between the outermost plate materials 1 and 3 becomes insufficient. For this reason, the upper limit with the preferable thickness is 3.0 mm, More preferably, it is 2.0 mm, More preferably, it is 1.6 mm.

また、内層(第2層)の板材2の厚み(内層が2層以上の場合は内層全体の厚み)は、最外層(第1層及び第3層)の板材1、3の各厚みに関連し、構造部品の設計仕様に応じて設定される。例えば、内層の板材2の全体の厚みは、実用的には、0.3mm〜2.4mmである。その厚みが薄過ぎると、強度を確保することができない。このため、その厚みの好ましい下限は、0.3mmであり、より好ましくは0.5mmである。一方、その厚みが厚過ぎると、スポット溶接時に電極からの加圧による最外層の板材1、3の変形量が過大になり、最外層の板材1、3同士の接触が不十分になる。このため、その厚みの好ましい上限は、2.4mmであり、より好ましくは1.8mmであり、更に好ましくは1.2mmである。   In addition, the thickness of the inner layer (second layer) plate 2 (the thickness of the entire inner layer when the inner layer is two or more) is related to the thickness of the outermost layers (first layer and third layer) of the plates 1 and 3. However, it is set according to the design specifications of the structural parts. For example, the entire thickness of the inner plate 2 is practically 0.3 mm to 2.4 mm. If the thickness is too thin, the strength cannot be ensured. For this reason, the minimum with the preferable thickness is 0.3 mm, More preferably, it is 0.5 mm. On the other hand, if the thickness is too thick, the deformation amount of the outermost plate materials 1 and 3 due to pressurization from the electrodes during spot welding becomes excessive, and the contact between the outermost plate materials 1 and 3 becomes insufficient. For this reason, the upper limit with the preferable thickness is 2.4 mm, More preferably, it is 1.8 mm, More preferably, it is 1.2 mm.

スポット溶接に用いられる電極20、20は、DR(ドームラジアス)型、CF(センターフラット)型、及びSR(シングルアール)型のいずれでもよい。DR型電極は、先端部がドーム状に突出した概ね円柱形状であって、その先端面が曲率半径の大きい凸曲面に形成されたものである。CF型電極は、先端部が円錐台状に突出した概ね円柱形状であって、その先端面が平坦面に形成されたものである。SR型電極は、概ね円柱形状であって、その先端面が一定の曲率半径の凸曲面に形成されたものである。   Electrodes 20 and 20 used for spot welding may be any of a DR (dome radius) type, a CF (center flat) type, and an SR (single are) type. The DR-type electrode has a generally cylindrical shape with a tip portion protruding in a dome shape, and the tip surface is formed in a convex curved surface having a large radius of curvature. The CF-type electrode has a substantially cylindrical shape with a tip portion protruding in a truncated cone shape, and the tip surface is formed into a flat surface. The SR-type electrode has a generally cylindrical shape, and its tip surface is formed as a convex curved surface with a constant radius of curvature.

ここで、上記した本実施形態のスポット溶接方法において、内層(第2層)の板材2に設けられた貫通穴2aの直径は、目標のナゲット径よりも大きいことが好ましい。その理由を以下に示す。   Here, in the spot welding method of the present embodiment described above, the diameter of the through hole 2a provided in the inner layer (second layer) plate 2 is preferably larger than the target nugget diameter. The reason is as follows.

一般に、スポット溶接によって構造部品を製造するにあたり、設計仕様により、目標のナゲット径(ナゲットの直径)NDaimが定められる。すなわち、スポット溶接によって形成されるナゲットは、目標のナゲット径NDaim以上であることが要求される。目標のナゲット径NDaimは、電極本体の直径Dよりも小さい。 Generally, when manufacturing a structural part by spot welding, a target nugget diameter (nugget diameter) ND aim is determined according to design specifications. That is, the nugget formed by spot welding is required to be not less than the target nugget diameter ND aim . The target nugget diameter ND aim is smaller than the diameter D of the electrode body.

通常、目標のナゲット径NDaimは、接合対象の板材の厚みt[mm]を指標とし、X√t[mm]で表される。その係数Xは、設計仕様により定められる。目標のナゲット径NDaimは、例えば5√tとされる。 Usually, the target nugget diameter ND aim is represented by X√t [mm] with the thickness t [mm] of the plate material to be joined as an index. The coefficient X is determined by design specifications. The target nugget diameter ND aim is, for example, 5√t.

これに対し、本実施形態のスポット溶接方法では、ナゲット4は、最外層(第1層及び第3層)の板材1、3の接触領域、すなわち、内層(第2層)の板材2における貫通穴2aの領域に形成される。したがって、目標のナゲット径NDaim以上のナゲット4を形成するために、貫通穴2aの直径(貫通穴が円形である場合)又は一辺の長さ(貫通穴が正方形である場合)は、目標のナゲット径NDaimよりも大きくする必要がある。より安全には、貫通穴2aの直径又は一辺の長さは、電極本体の直径D以上とすればよい。 On the other hand, in the spot welding method of this embodiment, the nugget 4 penetrates through the contact region of the outermost layer (first layer and third layer) plate materials 1 and 3, that is, the inner layer (second layer) plate material 2. It is formed in the region of the hole 2a. Therefore, in order to form a nugget 4 having a target nugget diameter ND aim or larger, the diameter of the through hole 2a (when the through hole is circular) or the length of one side (when the through hole is square) is The nugget diameter needs to be larger than the ND aim . More safely, the diameter or the length of one side of the through hole 2a may be greater than or equal to the diameter D of the electrode body.

ただし、貫通穴2aの直径又は一辺の長さがあまりに大きいと、外層(第1層及び第3層最)の板材1、3同士の接合による内層(第2層)の板材2の挟み込みが不十分になる。このため、その貫通穴2aの直径又は一辺の長さは、電極本体の直径Dの2.5倍以下であることが好ましい。   However, if the diameter or the length of one side of the through hole 2a is too large, the inner layer (second layer) plate material 2 is not sandwiched by joining the outer layer (first layer and third layer most) plate materials 1 and 3 together. It will be enough. For this reason, it is preferable that the diameter or the length of one side of the through-hole 2a is 2.5 times or less of the diameter D of the electrode body.

本発明の効果を確認するため、前記図1A〜図1Eに示す本実施形態のスポット溶接方法を適用し、下記の溶接試験を実施した。   In order to confirm the effect of the present invention, the spot welding method of the present embodiment shown in FIGS. 1A to 1E was applied, and the following welding test was performed.

[実施例1]
試験用の板材として、厚みが1.6mmである非めっきの高C含有鋼の板材(以下、「高C鋼板」ともいう)と、厚みが1.6mmである非めっきの低C含有鋼の板材(以下、「低C鋼板」ともいう)を多数準備した。高C鋼板の幾つかには、レーザカットにより直径が20mmの貫通穴を形成した。高C鋼板のC含有量は0.55質量%であった。低C鋼板のC含有量は0.01質量%未満であった。
[Example 1]
As a plate material for testing, a plate material of non-plated high C content steel having a thickness of 1.6 mm (hereinafter also referred to as “high C steel plate”) and a non-plated low C content steel having a thickness of 1.6 mm A large number of plate materials (hereinafter also referred to as “low-C steel plates”) were prepared. In some of the high C steel plates, through holes having a diameter of 20 mm were formed by laser cutting. The C content of the high C steel plate was 0.55% by mass. The C content of the low C steel plate was less than 0.01% by mass.

本発明例1として、穴なし高C鋼板、穴有り高C鋼板、及び穴なし低C鋼板を順に積み重ねた3層構造の板組を準備した。比較例1として、穴なし高C鋼板、及び穴なし高C鋼板を順に積み重ねた2層構造の板組を準備し、スポット溶接を行った。   As Example 1 of the present invention, a plate assembly having a three-layer structure in which a holeless high C steel plate, a holed high C steel plate, and a holeless low C steel plate were sequentially stacked was prepared. As Comparative Example 1, a plate assembly having a two-layer structure in which a holeless high C steel plate and a holeless high C steel plate were sequentially stacked was prepared, and spot welding was performed.

それぞれのスポット溶接では、溶接電流を種々変更した。共通する溶接条件は下記のとおりである。
・溶接機:単層交流電源のエアー加圧式スポット溶接機
・電極:DR型電極(先端面の直径:φ6mm、先端面の曲率半径:R40mm、本体直径:φ16mm)
・加圧力:400kgf(=3.92kN)
・通電時間:3層構造では40cycle、2層構造では20cycle(1cycleは1/60秒を意味する。)
In each spot welding, the welding current was changed variously. Common welding conditions are as follows.
-Welding machine: Air pressure type spot welding machine with single-layer AC power supply-Electrode: DR type electrode (tip end diameter: φ6mm, tip end curvature radius: R40mm, body diameter: φ16mm)
・ Pressure: 400kgf (= 3.92kN)
Energizing time: 40 cycles for a three-layer structure and 20 cycles for a two-layer structure (1 cycle means 1/60 second)

スポット溶接を行った後の各板組について、継手特性を評価した。継手特性の評価は、JIS Z3136に準拠した引張せん断強さ(TSS)で行った。更に、各板組について、ナゲットの中央を通るように切断し、その断面を鏡面研磨し、ナゲット(溶接金属)のビッカース硬さ(Hv)を測定した。ビッカース硬さの測定は、JIS Z2244に準拠して行った。試験荷重は1kgfとし、硬さは、測定した5点の平均値とした。下記の表2に試験条件と試験結果を示す。   Joint characteristics were evaluated for each plate assembly after spot welding. Evaluation of joint characteristics was performed by tensile shear strength (TSS) based on JIS Z3136. Further, each plate assembly was cut so as to pass through the center of the nugget, the cross section was mirror-polished, and the Vickers hardness (Hv) of the nugget (welded metal) was measured. Vickers hardness was measured according to JIS Z2244. The test load was 1 kgf, and the hardness was the average value of the five points measured. Table 2 below shows test conditions and test results.

Figure 2016128173
Figure 2016128173

表2に示す結果から以下のことが示される。本発明例1では、溶接金属のビッカース硬さが約600であり、第1層の高C鋼板のナゲット外周(溶接熱影響部)でプラグ破断した。これに対し、比較例1では、溶接金属のビッカース硬さが約750であり、高C鋼板同士の接合界面である溶接金属(ナゲット)内で脆性破断した。したがって、本発明例1の溶接条件に従えば、溶接金属の硬化を抑え、溶接金属内での脆性な破断を回避できることがわかった。   The results shown in Table 2 indicate the following. In Example 1 of the present invention, the Vickers hardness of the weld metal was about 600, and the plug broke at the outer periphery (welding heat affected zone) of the nugget of the high-C steel sheet of the first layer. On the other hand, in Comparative Example 1, the Vickers hardness of the weld metal was about 750, and the brittle fracture occurred in the weld metal (nugget) that is the joint interface between the high C steel plates. Therefore, according to the welding conditions of Example 1 of the present invention, it was found that hardening of the weld metal can be suppressed and brittle fracture in the weld metal can be avoided.

[実施例2]
試験用の板材として、厚みが1.6mmである高C鋼板と、厚みが1.4mmである低C鋼板を多数準備した。高C鋼板の幾つかには、上記実施例1と同様に貫通穴を形成した。高C鋼板のC含有量は0.55質量%であった。低C鋼板のC含有量は0.15質量%であった。
[Example 2]
A large number of high C steel plates having a thickness of 1.6 mm and low C steel plates having a thickness of 1.4 mm were prepared as test materials. In some of the high C steel plates, through holes were formed in the same manner as in Example 1 above. The C content of the high C steel plate was 0.55% by mass. The C content of the low C steel plate was 0.15% by mass.

本発明例2として、穴なし低C鋼板、穴有り高C鋼板、及び穴なし低C鋼板を順に積み重ねた3層構造の板組を準備した。比較例2として、穴なし高C鋼板、及び穴なし低C鋼板を順に積み重ねた2層構造の板組を準備し、スポット溶接を行った。   As Example 2 of the present invention, a plate assembly having a three-layer structure in which a low C steel plate without holes, a high C steel plate with holes, and a low C steel plate without holes was sequentially stacked was prepared. As Comparative Example 2, a plate assembly having a two-layer structure in which holeless high C steel plates and holeless low C steel plates were sequentially stacked was prepared, and spot welding was performed.

それぞれのスポット溶接では、上記実施例1と同様に溶接電流を種々変更した。共通する溶接条件、及び評価方法は上記実施例1と同様である。   In each spot welding, the welding current was variously changed as in Example 1. The common welding conditions and the evaluation method are the same as those in Example 1.

Figure 2016128173
Figure 2016128173

表3に示す結果から以下のことが示される。本発明例2では、溶接金属のビッカース硬さが約450であり、第1層の低C鋼板のナゲット外周でプラグ破断した。これに対し、比較例2では、溶接金属のビッカース硬さが約670であり、高C鋼板と低C鋼板の接合界面である溶接金属内で脆性破断した。したがって、本発明例2の溶接条件に従えば、溶接金属の硬化を抑え、溶接金属内での脆性な破断を回避できることがわかった。   The results shown in Table 3 indicate the following. In Example 2 of the present invention, the Vickers hardness of the weld metal was about 450, and the plug fracture occurred on the nugget periphery of the low-C steel sheet of the first layer. On the other hand, in Comparative Example 2, the Vickers hardness of the weld metal was about 670, and the brittle fracture occurred in the weld metal, which is the joint interface between the high C steel plate and the low C steel plate. Therefore, according to the welding conditions of Example 2 of the present invention, it has been found that hardening of the weld metal can be suppressed and brittle fracture in the weld metal can be avoided.

[実施例3]
試験用の板材として、厚みが1.4mmであるTWIP鋼板と、厚みが1.4mmである低合金鋼板を多数準備した。低合金板の幾つかには、上記実施例1と同様に貫通穴を形成した。TWIP鋼板について、C含有量は0.6質量%であり、Si含有量は0.3質量%であり、Mn含有量は20%であった。低合金鋼板について、C含有量は0.2質量%であり、Si含有量は0.05質量%であり、Mn含有量は1.2質量%であった。
[Example 3]
A large number of TWIP steel plates having a thickness of 1.4 mm and low alloy steel plates having a thickness of 1.4 mm were prepared as test plate materials. Through holes were formed in some of the low alloy plates in the same manner as in Example 1 above. For the TWIP steel sheet, the C content was 0.6% by mass, the Si content was 0.3% by mass, and the Mn content was 20%. About the low alloy steel plate, C content was 0.2 mass%, Si content was 0.05 mass%, and Mn content was 1.2 mass%.

本発明例3として、穴なしTWIP鋼板、穴有り低合金鋼板、及び穴なしTWIP鋼板を順に積み重ねた3層構造の板組を準備した。比較例3として、穴なしTWIP鋼板、及び穴なし低合金鋼板を順に積み重ねた2層構造の板組を準備し、スポット溶接を行った。   As Example 3 of the present invention, a plate assembly having a three-layer structure in which a holeless TWIP steel sheet, a holed low alloy steel sheet, and a holeless TWIP steel sheet were sequentially stacked was prepared. As Comparative Example 3, a plate assembly having a two-layer structure in which a holeless TWIP steel plate and a holeless low alloy steel plate were sequentially stacked was prepared, and spot welding was performed.

それぞれのスポット溶接では、上記実施例1と同様に溶接電流を種々変更した。共通する溶接条件、及び評価方法は上記実施例1と同様である。   In each spot welding, the welding current was variously changed as in Example 1. The common welding conditions and the evaluation method are the same as those in Example 1.

Figure 2016128173
Figure 2016128173

表4に示す結果から以下のことが示される。本発明例3では、溶接金属のビッカース硬さが約410であり、第1層のTWIP鋼板のナゲット外周でプラグ破断した。これに対し、比較例3では、溶接金属のビッカース硬さが約720であり、TWIP鋼板と低合金鋼板の接合界面である溶接金属内で脆性破断した。したがって、本発明例3の溶接条件に従えば、溶接金属の硬化を抑え、溶接金属内での脆性な破断を回避できることがわかった。   The results shown in Table 4 indicate the following. In Example 3 of the present invention, the Vickers hardness of the weld metal was about 410, and the plug broke on the outer periphery of the nugget of the TWIP steel sheet of the first layer. On the other hand, in Comparative Example 3, the Vickers hardness of the weld metal was about 720, and brittle fracture occurred in the weld metal, which is the joint interface between the TWIP steel plate and the low alloy steel plate. Therefore, according to the welding conditions of Example 3 of the present invention, it was found that hardening of the weld metal can be suppressed and brittle fracture in the weld metal can be avoided.

本発明は、あらゆる材料のスポット溶接に有効に利用できる。   The present invention can be effectively used for spot welding of all materials.

1:第1層(最外層)の板材、 2:第2層(内層)の板材、
2a:貫通穴、 3:第3層(最外層)の板材、 4:ナゲット、
10:板組の積層部、 20:電極
1: plate material of the first layer (outermost layer), 2: plate material of the second layer (inner layer),
2a: through hole, 3: plate material of third layer (outermost layer), 4: nugget,
10: Laminate part of plate assembly, 20: Electrode

Claims (10)

板材同士を接合するための抵抗スポット溶接方法であって、
少なくとも3層に板材が積み重ねられた積層部を含む板組を準備する準備工程と、
前記板組の前記積層部を一対の電極によって挟み込み、前記積層部を前記電極によって加圧しながら前記電極間に電流を印加して、前記積層部に抵抗スポット溶接を施す溶接工程と、を含み、
前記準備工程では、前記積層部として、最外層に互いに同種の金属の板材を配置するとともに、内層に前記最外層の板材のうちのいずれか一方の板材の材料と同一の材料の板材であって貫通穴を有する板材を配置し、
前記溶接工程では、前記内層の板材における前記貫通穴の位置と前記電極の位置を一致させた状態で抵抗スポット溶接を施す、抵抗スポット溶接方法。
A resistance spot welding method for joining plate materials,
A preparation step of preparing a plate assembly including a laminated portion in which plate materials are stacked in at least three layers;
A welding step of sandwiching the laminated portion of the plate set by a pair of electrodes, applying a current between the electrodes while pressing the laminated portion with the electrodes, and performing resistance spot welding on the laminated portion,
In the preparation step, as the laminated portion, the same kind of metal plate material is disposed in the outermost layer, and the inner layer is a plate material of the same material as the material of any one of the outermost layer plate materials, Place a plate material with a through hole,
A resistance spot welding method in which, in the welding step, resistance spot welding is performed in a state where the position of the through hole and the position of the electrode in the inner layer plate material are matched.
請求項1に記載の抵抗スポット溶接方法であって、
前記最外層の板材のうちのいずれか一方の板材の材料が高C含有鋼であり、他方の板材の材料が低C含有鋼である、抵抗スポット溶接方法。
The resistance spot welding method according to claim 1,
The resistance spot welding method, wherein a material of any one of the outermost plate materials is a high C-containing steel, and a material of the other plate material is a low C-containing steel.
板材同士を接合するための抵抗スポット溶接方法であって、
少なくとも3層に板材が積み重ねられた積層部を含む板組を準備する準備工程と、
前記板組の前記積層部を一対の電極によって挟み込み、前記積層部を前記電極によって加圧しながら前記電極間に電流を印加して、前記積層部に抵抗スポット溶接を施す溶接工程と、を含み、
前記準備工程では、前記積層部として、最外層に互いに同一の金属の板材を配置するとともに、内層に前記最外層の板材の材料と同種の材料の板材であって貫通穴を有する板材を配置し、
前記溶接工程では、前記内層の板材における前記貫通穴の位置と前記電極の位置を一致させた状態で抵抗スポット溶接を施す、抵抗スポット溶接方法。
A resistance spot welding method for joining plate materials,
A preparation step of preparing a plate assembly including a laminated portion in which plate materials are stacked in at least three layers;
A welding step of sandwiching the laminated portion of the plate set by a pair of electrodes, applying a current between the electrodes while pressing the laminated portion with the electrodes, and performing resistance spot welding on the laminated portion,
In the preparation step, as the laminated portion, the same metal plate material is arranged in the outermost layer, and a plate material of the same type as the material of the outermost layer plate material and having a through hole is arranged in the inner layer. ,
A resistance spot welding method in which, in the welding step, resistance spot welding is performed in a state where the position of the through hole and the position of the electrode in the inner layer plate material are matched.
請求項3に記載の抵抗スポット溶接方法であって、
前記最外層の板材の材料が低C含有鋼であり、前記内層の板材の材料が高C含有鋼である、抵抗スポット溶接方法。
The resistance spot welding method according to claim 3,
The resistance spot welding method, wherein the material of the outermost layer plate material is a low C content steel, and the material of the inner layer plate material is a high C content steel.
請求項3に記載の抵抗スポット溶接方法であって、
前記最外層の板材の材料が高合金鋼である、抵抗スポット溶接方法。
The resistance spot welding method according to claim 3,
The resistance spot welding method, wherein a material of the outermost layer plate material is high alloy steel.
板材同士を接合するための抵抗スポット溶接方法であって、
少なくとも3層に板材が積み重ねられた積層部を含む板組を準備する準備工程と、
前記板組の前記積層部を一対の電極によって挟み込み、前記積層部を前記電極によって加圧しながら前記電極間に電流を印加して、前記積層部に抵抗スポット溶接を施す溶接工程と、を含み、
前記準備工程では、前記積層部として、最外層に互いに同種の金属の板材を配置するとともに、内層に前記最外層の板材の材料と同種の材料の板材であって貫通穴を有する板材を配置し、
前記溶接工程では、前記内層の板材における前記貫通穴の位置と前記電極の位置を一致させた状態で抵抗スポット溶接を施す、抵抗スポット溶接方法。
A resistance spot welding method for joining plate materials,
A preparation step of preparing a plate assembly including a laminated portion in which plate materials are stacked in at least three layers;
A welding step of sandwiching the laminated portion of the plate set by a pair of electrodes, applying a current between the electrodes while pressing the laminated portion with the electrodes, and performing resistance spot welding on the laminated portion,
In the preparatory step, as the laminated portion, the same kind of metal plate material is arranged in the outermost layer, and the plate material of the same material as the material of the outermost layer plate material and having a through hole is arranged in the inner layer. ,
A resistance spot welding method in which, in the welding step, resistance spot welding is performed in a state where the position of the through hole and the position of the electrode in the inner layer plate material are matched.
請求項1〜6のいずれか1項に記載の抵抗スポット溶接方法であって、
前記内層の板材が絶縁被膜を有する、抵抗スポット溶接方法。
The resistance spot welding method according to any one of claims 1 to 6,
A resistance spot welding method, wherein the inner layer plate member has an insulating coating.
請求項1〜7のいずれか1項に記載の抵抗スポット溶接方法であって、
前記最外層の板材のうちのいずれか一方の板材が当て板である、抵抗スポット溶接方法。
The resistance spot welding method according to any one of claims 1 to 7,
The resistance spot welding method, wherein any one of the outermost plate members is a contact plate.
請求項1〜8のいずれか1項に記載の抵抗スポット溶接方法であって、
前記内層の板材における前記貫通穴の輪郭形状が円形又は正方形であり、前記貫通穴の直径又は一辺の長さが目標のナゲット径よりも大きい、抵抗スポット溶接方法。
A resistance spot welding method according to any one of claims 1 to 8,
The resistance spot welding method, wherein a contour shape of the through hole in the inner layer plate is circular or square, and a diameter or a side length of the through hole is larger than a target nugget diameter.
請求項1〜9のいずれか1項に記載の抵抗スポット溶接方法であって、
前記最外層の板材の各厚みが3.0mm以下であり、前記内層の板材の全体の厚みが2.4mm以下である、抵抗スポット溶接方法。
A resistance spot welding method according to any one of claims 1 to 9,
The resistance spot welding method in which each thickness of the plate material of the outermost layer is 3.0 mm or less, and the total thickness of the plate material of the inner layer is 2.4 mm or less.
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