JP2019098389A - Steel plate for spot welding - Google Patents
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本発明は、抵抗スポット溶接に供されるスポット溶接用鋼板に関するものである。 The present invention relates to a steel plate for spot welding to be subjected to resistance spot welding.
自動車の分野では、環境保全のため、車体の軽量化による燃費の向上とともに、衝突安全性の向上が求められている。そのため、高強度鋼板を使用して車体を薄肉化するとともに、車体構造を最適化して、車体の軽量化と衝突安全性の向上を図るために、これまで種々の取組みがなされている。 In the field of automobiles, in order to protect the environment, it is required to improve the collision safety as well as to improve the fuel efficiency by reducing the weight of the vehicle body. Therefore, various efforts have been made so far in order to reduce the thickness of the vehicle body by using a high strength steel plate and optimize the vehicle body structure to reduce the weight of the vehicle body and to improve the collision safety.
自動車等の溶接構造部材の製造や組立における溶接では、主に抵抗溶接によるスポット溶接が用いられているが、高強度鋼板のスポット溶接では次のような問題がある。
高強度鋼板はその強度を達成するために母材の炭素量等が大きくなっており、しかも、スポット溶接では溶接部は加熱後直ちに急冷されるために、高強度鋼板のスポット溶接部はマルテンサイト組織となり、溶接部及び熱影響部において硬度が上昇し、靭性が低下するようになる。また、溶接部では、局部的に生じる変態膨張と収縮により、溶接継手の引張残留応力が大きくなっている。
Although spot welding by resistance welding is mainly used for welding in the manufacture and assembly of welded structural members such as automobiles, spot welding of high strength steel plates has the following problems.
The high-strength steel sheet has a large carbon content in the base metal to achieve its strength, and in spot welding, the welded part is quenched immediately after heating, so the spot welded part of the high-strength steel sheet is martensite. It becomes a structure | tissue, hardness rises in a weld part and a heat affected zone, and toughness comes to fall. In addition, in the welded portion, the tensile residual stress of the welded joint is increased due to the locally generated transformation expansion and contraction.
このような高強度鋼板のスポット溶接の問題に対して、ナゲットを形成する本通電の後にさらに後通電（テンパー通電）を行う２段通電による方法がある。この方法では、後通電によりスポット溶接部（ナゲット部および熱影響部）を焼鈍して溶接部の硬さを低下させることができ、スポット溶接部の靭性を改善して継手強度を確保すことができる。 In order to solve the problem of spot welding of such a high strength steel plate, there is a method by two-stage energization in which post-energization (temper energization) is further performed after main energization to form a nugget. In this method, the spot welds (nugget and heat affected zone) can be annealed by post-energization to reduce the hardness of the weld, and the toughness of the spot weld can be improved to secure the joint strength. it can.
一方、高強度鋼板をスポット溶接した場合において、遅れ破壊（水素脆化割れ）の問題もある。
遅れ破壊は、鋼板の硬さ、残留応力、そして鋼板中の水素量の３因子に主に支配されるが、スポット溶接部は、硬度が高く、引張残留応力が大きくなっているので、水素侵入が起これば、遅れ破壊を引き起こしやすい部位となっている。
遅れ破壊が発生すると、割れがナゲットや熱影響部を横断し、継手を破断させてしまう場合や、ナゲット内もしくは熱影響部内で割れが止まったとしても継手の強度を低下させる可能性が高い。さらに、割れの部分に水分が浸入すると、腐食が発生して強度がさらに低下するという問題が生じる。これらの問題が、高強度鋼板の適用による車体の軽量化（薄肉化）を阻害する一因となっている。
On the other hand, there is also a problem of delayed fracture (hydrogen embrittlement cracking) when spot welding a high strength steel plate.
Delayed fracture is mainly governed by three factors: hardness of steel plate, residual stress, and amount of hydrogen in steel plate, but since spot welds have high hardness and large tensile residual stress, hydrogen penetration If it happens, it is a site that is likely to cause delayed destruction.
If delayed fracture occurs, a crack may cross the nugget or heat-affected zone and break the joint, or even if the crack stops in the nugget or in the heat-affected zone, the joint strength may be reduced. Furthermore, if water intrudes into the cracked part, corrosion occurs and the strength is further reduced. These problems are one of the factors that inhibit the weight reduction (thinning) of the vehicle body by the application of high strength steel plates.
このような問題に対して、特許文献１には、ナゲットを形成する本通電後の後通電時において、本通電時の加圧力Ｐ１よりも加圧力を上昇させて、高い加圧力Ｐ２で加圧することにより、溶接部周辺に圧縮残留応力を導入して耐遅れ破壊特性を向上させるスポット溶接技術が開示されている。 In order to address such a problem, according to Patent Document 1, at the time of post-energization after the main energization forming the nugget, the pressurizing force is increased more than the pressurizing force P1 at the time of main energization, and pressurization is performed with high pressurizing force P2. Thus, a spot welding technique is disclosed that introduces compressive residual stress around the weld to improve delayed fracture resistance.
特許文献１に開示の技術は、溶接部の引張残留応力を低減できるため、遅れ破壊の抑制に対して有効な技術であるが、溶接の際に溶接部などに侵入する水素量の影響については特に考慮されておらず、溶接時の水素侵入抑制の観点から水素脆化割れを抑制することが望まれる。
本発明では、このような実情に鑑み、鋼板をスポット溶接する際、遅れ破壊の要因の一つである水素の侵入を抑制できるスポット溶接用鋼板を提供することを課題とする。
The technology disclosed in Patent Document 1 is an effective technology for suppressing delayed fracture because it can reduce tensile residual stress in the weld, but the effect of the amount of hydrogen entering the weld or the like at the time of welding Not particularly considered, it is desirable to suppress hydrogen embrittlement cracking from the viewpoint of suppressing hydrogen penetration at the time of welding.
In the present invention, it is an object of the present invention to provide a steel plate for spot welding which can suppress the penetration of hydrogen which is one of the causes of delayed fracture when spot welding a steel plate in view of such a situation.
一般にスポット溶接前の鋼板は、防錆油、洗浄油や加工油などの油（以下、単に「油」と記載）が表面に塗られた状態あるいは残留した状態で保管されている。油はスポット溶接の熱により揮発して除去されるため、通常は鋼板に付着している油を除去しないでスポット溶接が行われている。 In general, steel plates prior to spot welding are stored in a state in which an oil such as a rustproof oil, a cleaning oil or a processing oil (hereinafter simply referred to as "oil") is applied or remains on the surface. Since oil is volatilized and removed by the heat of spot welding, spot welding is usually performed without removing oil adhering to the steel sheet.
本発明者らは、そのような油が鋼板への水素侵入の要因になるのではないかと考え、油が付着したままの鋼板をスポット溶接した場合の水素の影響について調査した。
その結果、鋼板の合わせ面の間に油が付着したままの鋼板をスポット溶接すると溶接部に水素が侵入することを見出した。
そして、溶接時に侵入する水素量を低減する手段について検討する過程で、スポット溶接の初期加圧時に、接触した鋼板間に油が閉じ込められることが原因で水素が鋼板内に侵入すること、及び、スポット溶接用の鋼板として、溶接個所となる鋼板表面に予め連続的な凹部を複数形成した鋼板を用いれば、その連続的な凹部が、油を溶接部外に排出する通路として機能し、それにより鋼板内への水素の侵入を抑制できることを見出した。
The present inventors considered that such oil might be a factor of hydrogen penetration to a steel plate, and investigated the effect of hydrogen when spot welding a steel plate with oil attached.
As a result, it was found that when spot welding a steel sheet with oil attached between the mating surfaces of the steel sheets, hydrogen penetrates the weld.
Then, in the process of examining means for reducing the amount of hydrogen intruding at the time of welding, hydrogen intrudes into the steel plate due to oil being trapped between the steel plates in contact at the time of initial pressurization of spot welding; When a steel plate in which a plurality of continuous recesses are formed in advance on the surface of a steel plate to be welded is used as a steel plate for spot welding, the continuous recesses function as a passage for discharging oil out of the welding portion It has been found that the penetration of hydrogen into the steel sheet can be suppressed.
本発明は、このような知見に基づいてなされたもので、その要旨は以下の通りである。
（１）スポット溶接に用いられる鋼板であって、該鋼板表面に凹凸模様が形成されており、
鋼板表面の任意の個所を直径が５ｍｍと２ｍｍの同心円で区切ったとき、前記凹凸模様の凹部によって、前記直径２ｍｍの円内を通り、前記直径５ｍｍの円を貫通して連続する通路が複数形成されており、
該通路は、スポット溶接時に、鋼板合わせ面に存在する油が前記接触部外に出て行く通路となることを特徴とするスポット溶接用鋼板。
The present invention has been made based on such findings, and the summary thereof is as follows.
(1) A steel plate used for spot welding, in which a concavo-convex pattern is formed on the surface of the steel plate,
When an arbitrary point on the surface of the steel plate is divided by concentric circles of 5 mm and 2 mm in diameter, a plurality of continuous passages are formed by passing through the circle of 2 mm in diameter and the circle of 5 mm in diameter Has been
A steel plate for spot welding, wherein the passage serves as a passage through which oil present in the steel plate mating surface goes out of the contact portion during spot welding.
（２）前記凹凸模様は、表面に１ｍｍ以下の間隔で設けられた筋状の凸部と凸部間の前記通路を形成する凹部よりなり、前記凸部の高さは、２μm以上１００μm以下であることを特徴とする上記（１）に記載のスポット溶接鋼板。
（３）前記凹凸模様は、表面に１ｍｍ以下の間隔で設けられた筋状の凸部と凸部間の前記通路を形成する凹部よりなり、前記凸部の高さは、２μｍ以上１００μｍ以下であることを特徴とする上記（１）に記載のスポット溶接鋼板。
（４）前記筋状の凹部または凸部は、互いに交差して設けられていることを特徴とする上記（２）または（３）に記載のスポット溶接用鋼板。
(2) The concavo-convex pattern is composed of a ridge formed on the surface at intervals of 1 mm or less and a recess forming the passage between the protrusions, and the height of the ridge is 2 μm to 100 μm. The spot welded steel sheet according to the above (1), characterized in that
(3) The concavo-convex pattern is composed of a ridge formed on the surface at intervals of 1 mm or less and a recess forming the passage between the protrusions, and the height of the ridge is 2 μm or more and 100 μm or less The spot welded steel sheet according to the above (1), characterized in that
(4) The steel plate for spot welding according to (2) or (3) above, wherein the streak-like concave portions or convex portions are provided so as to cross each other.
（５）前記凹凸模様は、島状の凸部と、凸部間の前記通路を形成する凹部よりなり、該凹部の幅は１ｍｍ以下であり、前記凸部の高さは２μm以上１００μm以下であることを特徴とする上記（１）に記載のスポット溶接用鋼板。 (5) The concavo-convex pattern includes an island-shaped convex portion and a concave portion forming the passage between the convex portions, the width of the concave portion is 1 mm or less, and the height of the convex portion is 2 μm to 100 μm. The steel plate for spot welding as described in (1) above, characterized in that
表面に油が付着したままの鋼板を用いて、スポット溶接により溶接構造部材を製造する際、本発明の鋼板を用いることにより、溶接部の合わせ面に予め形成されている連続的な凹部を通して油が溶接部外へ排出されるので、スポット溶接部に水素が侵入し難くなる。その結果、溶接部への水素の侵入を抑制できるので、溶接時に侵入する水素による水素脆化割れを抑制した溶接構造部材を得ることができる。 When manufacturing a welded structural member by spot welding using a steel plate with oil adhering to the surface, the oil of the present invention can be obtained by using the steel plate of the present invention, through the continuous recesses formed in advance in the mating surfaces of the welds Since the hydrogen is discharged out of the weld, it is difficult for hydrogen to penetrate the spot weld. As a result, since it is possible to suppress the penetration of hydrogen into the weld, it is possible to obtain a welded structural member in which the hydrogen embrittlement crack caused by the hydrogen entering during welding is suppressed.
本発明の鋼板は表面に凹凸模様が形成されている。そのような鋼板を重ね合わせてスポット溶接する場合、合せ面となる鋼板面の一方または両方であって、スポット溶接の初期加圧時の鋼板どうしが接触して接触部となる箇所に、該接触部を通り、接触部外に連なる複数の凹部（線状の溝）が存在しているので、鋼板に油が塗布されていても、通電時に、塗布されていた油を接触部から外部に排出できるようにして、油が接触部に閉じ込められて溶接部へ水素が侵入するのを抑制できるものである。
最初に、表面に油が付着したままの鋼板をスポット溶接しても、油に由来する水素の侵入を防止できるような本発明の鋼板を見出すに至った試験について説明する。
An uneven pattern is formed on the surface of the steel plate of the present invention. When such steel plates are stacked and spot-welded, the contact is made to one or both of the steel plate surfaces serving as mating surfaces, where the steel plates at initial pressure application in spot welding come in contact with each other to form contact portions. Because there are a plurality of recesses (linear grooves) that run outside the contact part through the part, even when oil is applied to the steel plate, the oil that has been applied is discharged from the contact part to the outside at the time of energization It is possible to prevent oil from being trapped in the contact portion and hydrogen entering the weld portion.
First, a test that has led to the finding of a steel plate of the present invention that can prevent the penetration of hydrogen derived from oil even if spot welding a steel plate with oil adhering to the surface will be described.
自動車用部材のスポット溶接による組立てでは、鋼板部材は油が塗布されたままでスポット溶接工程に供される。そこで、まず、油が水素の侵入源になるかどうかを調べた。
実験に当たり、試験片として、次に示すような大きさが３０ｍｍ×３０ｍｍの３種類の試験片を準備した。油としては防錆油（パーカー興産株式会社製 NOX-RUST530F(60) ）を使用した。
・板厚１ｍｍの鋼板を、各鋼板の両面に油を塗布して２枚重ねた試験片Ａ１
・板厚１ｍｍの鋼板を２枚重ねた試験片Ａ２（各鋼板の両面とも油の塗布なし）
・板厚２ｍｍの鋼板１枚よりなる試験片Ｂ（鋼板の両面とも油を塗布）
In the spot welding assembly of automobile parts, the steel sheet members are subjected to a spot welding process with oil applied. Therefore, first, it was investigated whether oil was a source of hydrogen penetration.
In the experiment, three kinds of test pieces of 30 mm × 30 mm in size as shown below were prepared as test pieces. As the oil, a rustproof oil (NOX-RUST 530F (60) manufactured by Parker Kosan Co., Ltd.) was used.
A test piece A1 in which oil is applied to both sides of each steel plate and two sheets of steel plates each having a thickness of 1 mm are stacked
· Test piece A2 in which two steel plates having a thickness of 1 mm are stacked (with no oil applied on both sides of each steel plate)
· Test piece B consisting of one steel plate of 2 mm thickness (both sides of steel plate coated with oil)
試験片Ａ１、Ａ２を、下記表１の共通溶接条件の下で、加圧力を一定として、溶接電流を変化させてスポット溶接して、３√ｔ、４√ｔ、５√ｔ径のナゲットをそれぞれ形成した後、直ちに液体窒素にて冷却した。なお、板厚ｔは１ｍｍである。その後、溶接後の試験片を、ナゲットを含むように１０ｍｍ×１０ｍｍの大きさに切断した。
溶接後の試験片Ａ１、Ａ２における侵入水素量測定は、試験片を昇温することで水素を放出させ、この放出した水素量をガスクロマトグラフによって測定することで行った。昇温速度は１００℃／hour、最高到達温度は２００℃とし、２００℃までに放出された水素量を侵入水素量とした。また、試験片Ｂをスポット溶接と同様に加圧・通電して同様の径のナゲットをそれぞれ形成し、通電後の試験片Ｂが有する水素量を同様に測定した。試験片Ａ１、Ａ２での結果を図１に示す。
The test pieces A1 and A2 are spot welded under the common welding conditions shown in the following Table 1 while changing the welding current with constant applied pressure and nuggets of 33t, 4 、 t, 5√t diameter After each formation, it was immediately cooled with liquid nitrogen. The plate thickness t is 1 mm. Thereafter, the test pieces after welding were cut into a size of 10 mm × 10 mm so as to include nuggets.
The measurement of the amount of intruding hydrogen in the test pieces A1 and A2 after welding was performed by releasing hydrogen by raising the temperature of the test pieces and measuring the amount of released hydrogen by gas chromatography. The heating rate was 100 ° C./hour, the maximum temperature reached was 200 ° C., and the amount of hydrogen released up to 200 ° C. was taken as the amount of intruding hydrogen. Moreover, the test piece B was pressurized and energized in the same manner as spot welding to form nuggets of the same diameter, and the hydrogen content of the test strip B after energization was measured in the same manner. The results for the test pieces A1 and A2 are shown in FIG.
油を塗布された試験片Ａ１では、図１ａに示されるように、３√ｔ〜５√ｔのすべての径のナゲットで、０．２５μｇ以上の水素量が検出されたが、油の塗布がない試験片Ａ２では、図１ｂに示されるように、ナゲット径４√ｔで多少の水素が検出されたものの、他の径では水素は検出されなかった。また、試験片Ｂではいずれのナゲット径でも水素は検出されなかった。
ちなみに、試験片Ａ１のナゲット径３√ｔでの水素量を、ナゲットにのみ水素が侵入したと仮定して水素濃度を計算すると、３．８ｐｐｍという非常に高い濃度になり、遅れ破壊の要因になる可能性が高いことが見出された。
In the oil-coated test piece A1, as shown in FIG. 1a, a hydrogen amount of 0.25 μg or more was detected in nuggets of all diameters from 3√t to 5√t, but the oil application was In the case of no test piece A2, as shown in FIG. 1b, although some hydrogen was detected at a nugget diameter of 4 水 素 t, no hydrogen was detected at other diameters. Further, in the test piece B, hydrogen was not detected at any nugget diameter.
Incidentally, when the hydrogen concentration is calculated on the assumption that hydrogen penetrates into the nugget only at the nugget diameter of 3 試 験 t of the test piece A1, the concentration becomes as high as 3.8 ppm, which is a factor of delayed fracture. Was found to be likely.
以上の結果から、スポット溶接における鋼板合わせ面の間に油が存在すると、溶接後の鋼板における侵入水素量が顕著に増加することが知見された。また、試験片Ｂの結果から、鋼板の電極側の表面からは水素が侵入しないことも知見された。 From the above results, it was found that the presence of oil between the steel plate mating surfaces in spot welding significantly increases the amount of intruding hydrogen in the steel plate after welding. Moreover, from the result of the test piece B, it was also found that hydrogen does not infiltrate from the surface of the steel plate on the electrode side.
この試験より、鋼板合わせ面の間に存在する油が水素の侵入源になることが認められたので、次に、油に由来する水素が、スポット溶接の際に鋼板内に侵入するメカニズムについて調べた。 From this test, it was recognized that the oil present between the steel sheet mating surfaces was the penetration source of hydrogen, so next, the mechanism by which hydrogen derived from oil penetrates into the steel sheet at the time of spot welding is examined The
図１ａの結果では、ナゲット径と侵入水素量との関連は認められなかったので、鋼板の合わせ面の間に油が存在する場合の初期加圧時の接触部の面積と溶接後の侵入水素量との関連を検討した。
まず、２枚の鋼板の間に感圧紙を挟み込んで、それらを重ね合わせ、重ねた鋼板の両側からスポット溶接電極で加圧力２００ｋｇｆと４００ｋｇｆで加圧した時の鋼板接触部の面積を測定した。次に、合わせ面側に油を塗布した鋼板を同じ加圧力で加圧するスポット溶接を行い、溶接後それぞれの鋼板の水素量を昇温脱離法によって測定した。結果を表２に示す。
表２から、スポット溶接の初期加圧時に接触する鋼板部分（接触部）の面積が大きくなると、鋼板内に侵入する水素量も増加することが知見された。
Since the relationship between the nugget diameter and the amount of invading hydrogen was not found in the results of FIG. 1a, the area of the contact portion at the time of initial pressurization and the intruding hydrogen after welding when oil is present between the mating surfaces of the steel plates. The relationship with the amount was examined.
First, a pressure-sensitive paper was sandwiched between two steel plates, these were stacked, and the area of the steel plate contact portion was measured when applied with pressure of 200 kgf and 400 kgf with spot welding electrodes from both sides of the stacked steel plates. Next, spot welding was performed in which steel plates coated with oil on the mating surface side were pressurized with the same pressure, and the hydrogen content of each steel plate after welding was measured by a temperature rising desorption method. The results are shown in Table 2.
From Table 2, it was found that when the area of the steel plate portion (contact portion) in contact at the time of initial pressurization of spot welding is increased, the amount of hydrogen intruding into the steel plate is also increased.
この試験より、接触部の面積が大きくなると、接触部に閉じ込められる油量が増加して、鋼板内に侵入する水素量も増加すると考えられることや、ナゲット径と侵入水素量の間には相関がみられないことから、加圧初期に接触した鋼板間に保持される油量が侵入水素量を決定すると考えられる。
すなわち、図２に示すように、鋼板３、４の合わせ面５に油が塗布されている場合、電極１、２による鋼板３、４の初期加圧時に、接触した鋼板間（接触部）に油が閉じ込められ、その閉じ込められた油は、通電加熱時に接触部から外部に排出されず、熱により分解して溶接部に侵入することが原因で鋼板への侵入水素量が増加すると考えられた。
According to this test, when the area of the contact portion is increased, the amount of oil trapped in the contact portion is increased, and the amount of hydrogen intruding into the steel plate is also considered to be increased. It can be considered that the amount of oil held between the steel plates contacted at the initial stage of pressing determines the amount of intruding hydrogen, since it can not be seen.
That is, as shown in FIG. 2, when oil is applied to the mating surface 5 of the
そこで、加圧初期の鋼板が接触する際に、油を鋼板接触部内から外に排出する手段について検討した結果、予め油を接触部外に排出できる通路を、接触部を通り接触部外に連なるように鋼板表面に形成することを着想し、以下の試験を行った。 Therefore, as a result of examining the means for discharging the oil from the inside of the steel plate contact portion to the outside when the steel plate in the initial stage of the pressure contact, the passage through which the oil can be discharged to the outside of the contact portion Based on the idea of forming on the surface of a steel sheet, the following tests were conducted.
通路を形成した鋼板として、大きさが３０×３０ｍｍで板厚１ｍｍの鋼板の片側表面全体に、次の条件（ａ）、（ｂ）で筋状の凹部を有する凹凸模様を罫書き加工により施工した鋼板を準備した（図４ａ参照）。比較のために、凹凸模様を施工しない鋼板も準備した。
（ａ）幅０．１ｍｍ、深さが０．１ｍｍの平行な筋状の凹部を０．７ｍｍピッチで施工
（ｂ）幅０．１ｍｍ、深さが０．１ｍｍの平行な筋状の凹部を０．３５ｍｍピッチで施工
As a steel plate in which a passage is formed, a concavo-convex pattern having streak-like concaves under the following conditions (a) and (b) is applied by scribing on the entire surface of one side of a steel plate having a size of 30 × 30 mm and a thickness of 1 mm. The prepared steel plate was prepared (see FIG. 4a). The steel plate which does not construct a concavo-convex pattern was also prepared for comparison.
(A) Install parallel streak-shaped recesses with a width of 0.1 mm and depth of 0.1 mm at a pitch of 0.7 mm. (B) Parallel streak-shaped recesses with a width of 0.1 mm and a depth of 0.1 mm. Construction with 0.35 mm pitch
凹部なしの鋼板２枚を合わせ面の間に油を介在させて積層した鋼板と、片側に凹部を施工した２枚の鋼板をそれぞれ凹部加工面が上側になるように、すなわち凹部加工がされていない面と凹部加工がされた面が重ね面となるように積層するとともに合わせ面の間に油を介在させて積層した鋼板をそれぞれ複数準備し、それぞれの積層した鋼板の中央部を表３の条件でスポット溶接した。 A steel plate in which oil is interposed between two steel plates without concaves and laminated, and a steel plate with concaves on one side are concaved so that the concaved surface is on the upper side, that is, concaved A plurality of steel plates laminated so that there is no surface and a surface subjected to concave processing as overlapping surfaces and oil is interposed between the mating surfaces are prepared respectively, and the central portion of each laminated steel plate is shown in Table 3 Spot welding was performed under the conditions.
それぞれの積層した鋼板について水素の侵入量を測定した結果（複数の平均値）を図３に示す。
合わせ面に筋状の凹部を形成した鋼板では、極めて低い侵入水素量となり、油が凹部に沿って接触部外に排出されたことが推測された。
以上の結果から、油に起因する鋼板への水素侵入を防止するには、油を鋼板接触部内から外部に排出する通路を形成することの有効性が確認された。
The result (a plurality of average values) of measuring the penetration amount of hydrogen for each laminated steel plate is shown in FIG.
In the steel plate in which the streak-like concave portion was formed on the mating surface, it was estimated that the amount of intruding hydrogen was extremely low, and the oil was discharged out of the contact portion along the concave portion.
From the above results, the effectiveness of forming a passage for discharging oil from the inside of the steel plate contact portion to the outside was confirmed in order to prevent hydrogen penetration into the steel plate due to oil.
以上のように、筋状の凹部を形成することの有効性が確認されたので、凹部を含む凹凸模様の形態及び凹凸模様を効率的に形成する手段についてさらに検討した。
凹凸模様を形成する範囲は、スポット溶接の電極による加圧初期に、鋼板合わせ面で鋼板が接触する範囲を少なくとも超える範囲とする必要がある。
スポット溶接打点が多い溶接組立て部材では、溶接箇所ごとに凹凸模様を形成するのは効率的ではない。
そこで、スポット溶接に供される鋼板（スポット溶接用鋼板）の表面全体に予め油排出用の通路となる凹凸模様を形成しておけば、鋼板のどこがスポット溶接箇所となっても、必ず溶接個所に通路が位置することになることを着想した。そして、鋼板面全体に凹凸模様を形成する場合の最適な形態についてさらに検討して本発明に到達した。
以下、そのようになされた本発明の要件や好ましい要件について説明する。
As described above, since the effectiveness of forming the streak-like recess was confirmed, the form of the concavo-convex pattern including the concavities and the means for efficiently forming the concavo-convex pattern were further examined.
It is necessary to make the range which forms a concavo-convex pattern at least the range which exceeds the range which a steel plate contacts in a steel plate joint side at the initial stage of pressurization by the electrode of spot welding.
In the case of a welded assembly having many spot welds, it is not efficient to form a concavo-convex pattern for each weld.
Therefore, if a concavo-convex pattern to be a passage for oil discharge is formed in advance on the entire surface of the steel plate (steel plate for spot welding) to be subjected to spot welding, the welding spot is always required regardless of where on the steel plate becomes a spot welding location. I thought that the passage would be located. Then, the present invention has been reached by further examining an optimal form in the case of forming a concavo-convex pattern on the entire surface of a steel sheet.
Hereinafter, the requirements and preferable requirements of the present invention made as such will be described.
（凹凸模様を形成する範囲）
スポット溶接時に油を排出する通路となる凹凸模様を形成する範囲は、鋼板表面全体とする。鋼板全体に予め凹凸模様を形成しておけば、溶接構造物の形状にかかわらず、スポット溶接時の鋼板接触面には、油排出用の通路が形成されているので、油による鋼板への水素侵入を防ぐことができる。
なお、凹凸模様を形成する鋼板表面は両面でも片面でもよいが、片面であれば、凹凸模様を形成した面がスポット溶接時に合わせ面となるように管理する必要がある。
(The range which forms a concavo-convex pattern)
The range which forms the uneven | corrugated pattern used as the channel | path which discharge | releases oil at the time of spot welding is made into the whole steel plate surface. If a concavo-convex pattern is formed in advance on the entire steel plate, regardless of the shape of the welded structure, a passage for oil discharge is formed on the steel plate contact surface at the time of spot welding. It can prevent intrusion.
In addition, although the steel plate surface which forms an uneven | corrugated pattern may be both surfaces or single side, if it is single side, it is necessary to manage so that the surface which formed the uneven pattern becomes a mating surface at the time of spot welding.
（凹凸模様の形態）
凹凸模様は、スポット溶接時に鋼板接触面に油の通る通路が形成されるものであれば、特定の形状に限定されるものではないが、筋状の連続的な凹部や凸部を縞状に形成する例や、島状の凸部を形成する例が例示される。
図４、５に凹凸模様の代表的な形態を示す。
(Form of unevenness pattern)
The concavo-convex pattern is not limited to a specific shape as long as a passage through which oil passes is formed on the steel plate contact surface at the time of spot welding, but streaks of continuous concave and convex portions are striped. An example to form and an example to form an island-like convex part are illustrated.
4 and 5 show representative forms of the concavo-convex pattern.
図４ａ〜ｃは、凹部と凸部が縞状に形成された例を示し、ａは凹凸部が鋼板長手方向に平行に形成された例、ｂは鋼板長手方向に垂直に形成された例、ｃは斜め方向に形成された例を示し、図４ｄは凹凸部が格子状に形成された例を示す。
また、図５は、凸部が島状に形成され、ａは凸部が縞状に配列している例、ｂは凸部が格子状に配列している例、ｃは凸部が水玉状に配列している例をそれぞれ示す。
図４ｄの格子状、図５ａ〜ｃの島状の凹凸模様では、図５ｃで例示するように多方面に通路８を形成することができる。
FIGS. 4a to 4c show an example in which the recess and the protrusion are formed in stripes, where a is an example in which the asperities are formed parallel to the longitudinal direction of the steel plate, b is an example formed perpendicularly to the longitudinal direction of the steel plate, c shows the example formed in the diagonal direction, FIG. 4 d shows the example in which the uneven | corrugated | grooved part was formed in the grid | lattice form.
Further, FIG. 5 shows an example in which the convex portions are formed in an island shape and a is an example in which the convex portions are arranged in a stripe, b is an example in which the convex portions are arranged in a lattice The example arranged in is shown respectively.
In the grid-like shape of FIG. 4 d and the island-like concavo-convex pattern of FIG. 5 a-c, the
（凹部の要件）
鋼板の表面に形成された凹凸模様の凹部は、スポット溶接時に少なくとも鋼板接触部の内部から接触部外に連通していることが必要である。
このためには、鋼板表面の任意の個所を直径５ｍｍと２ｍｍの同心円で区切ったとき、凹凸模様の凹部によって、直径５ｍｍの円で囲まれた領域外から該円を貫通して連続する通路が複数形成されており、かつ、その中の少なくとも２本の通路は、直径２ｍｍの円内を通ることが必要である。なお、円内を通るとは、凹部の幅の少なくとも半分が円に係っていることをいう。
図６ａ、ｂに、図４ａと図５ｂの場合について、通路と直径５ｍｍと２ｍｍの同心円の関係を示す。
(Recess requirements)
At the time of spot welding, at least the inside of the contact portion of the steel plate needs to be in communication with the outside of the contact portion at the time of spot welding.
For this purpose, when an arbitrary portion on the surface of the steel plate is divided by concentric circles of 5 mm and 2 mm in diameter, the concave and convex pattern has a continuous passage penetrating the circle from outside the area surrounded by the circle of 5 mm in diameter. It is necessary that a plurality of passages be formed, and at least two of the passages pass through a circle having a diameter of 2 mm. In addition, passing through the inside of a circle means that at least half of the width of the recess is associated with the circle.
6a, b show the relationship between the passage and concentric circles of 5 mm and 2 mm diameter for the cases of FIGS. 4a and 5b.
スポット溶接の際の初期接触部の径は通常２〜５ｍｍの範囲で形成されるので、凹部による通路が、前記の条件を満たすように鋼板表面に形成されていれば、鋼板のどの部分がスポット溶接個所となっても、その個所は、スポット溶接時に、鋼板合わせ面に存在する油が前記鋼板接触部外に出て行く通路を有することになる。 The diameter of the initial contact portion at the time of spot welding is usually formed in the range of 2 to 5 mm, so if the passage by the recess is formed on the steel sheet surface to satisfy the above conditions, which part of the steel sheet is spotted Even in the case of welding, the spot has a passage through which the oil present on the steel plate mating surface comes out of the steel plate contact portion during spot welding.
また、個々の凹部の幅や深さは、油を効率的に排出するために、次の条件が好ましい。
図４で示す筋状の凹部を用いた凹凸模様では、各凹部は１ｍｍ以下の間隔で設けられ、各凹部の深さは、２μm以上１００μm以下であることが好ましい。凸部を形成した場合でも同様である。
また、図５で示す島状の凸部を用いた凹凸模様は、島状の凸部と凸部間の凹部の幅は、最大１ｍｍ以下であり、前記凸部の高さは２μm以上１００μm以下であることが好ましい。
なお、凹部あるいは凸部の深さや幅は、鋼板表面をレーザ顕微鏡で観察する方法や、撮像して画像処理する方法などで測定できる。
Moreover, the following conditions are preferable in order to discharge | emit oil efficiently the width | variety and the depth of each recessed part.
In the concavo-convex pattern using the streaky concave portions shown in FIG. 4, it is preferable that the respective concave portions be provided at an interval of 1 mm or less, and the depth of each concave portion be 2 μm or more and 100 μm or less. The same applies to the case where a convex portion is formed.
Further, in the concavo-convex pattern using the island-like convex portion shown in FIG. 5, the width of the concave portion between the island-like convex portion and the convex portion is at most 1 mm or less, and the height of the convex portion is 2 μm to 100 μm Is preferred.
In addition, the depth and width of a recessed part or a convex part can be measured by the method of observing a steel plate surface with a laser microscope, the method of imaging and processing an image, etc.
（凹凸模様の形成方法）
鋼板全面に凹部を加工に適する方法としては、所定の凹凸模様が表面に形成されたロールを用いて圧延またはロール加工する方法、所定の凹凸模様が表面に形成された金型でスタンピング加工する方法、多数の罫書き針をブラシ状に配置した装置により筋状の凹部をけがく方法などがあり、これらの方法が適宜採用できる。
(Formation method of unevenness pattern)
As a method suitable for processing the recess on the entire surface of the steel plate, there is a method of rolling or rolling using a roll having a predetermined concavo-convex pattern formed on the surface, a method of stamping using a mold having a predetermined concavo-convex pattern formed on the surface There is, for example, a method of scribing a streak-like concave portion by an apparatus in which a large number of scribing needles are arranged in a brush shape, and these methods can be appropriately adopted.
（その他）
本発明のスポット溶接用鋼板は、溶接組立てする製品の形状・構造に合わせて、所定の形状に切り出されたり、その後に所定の形状に成形されたりしてスポット溶接に供される。
(Others)
The steel plate for spot welding of the present invention is subjected to spot welding by being cut out into a predetermined shape or thereafter formed into a predetermined shape according to the shape and structure of the product to be welded and assembled.
板厚が１ｍｍの鋼板の片側の表面のみに、ロール加工、スタンピング加工、罫書き加工により表面に凹凸模様を形成した後、熱処理により強度を９８０ＭＰａに調整した。
加工した凹凸模様は、図４ａ〜ｄ、図７ａ〜ｃに示される一定パターンとした。
図４ａ〜ｄの筋状のパターンは罫書き加工、スタンピング加工で作製し、図７ａ〜ｃの島状のパターンはロール加工、スタンピング加工で作製した。
なお、島状のパターンの凹部の幅Ｄや、凸部の長さ、幅、間隔は、図７ａ〜ｃの矢印で示すとおりとした。
An uneven pattern was formed on the surface of the steel plate having a thickness of 1 mm only by rolling, stamping and scribing, and then the strength was adjusted to 980 MPa by heat treatment.
The processed uneven | corrugated pattern was taken as the fixed pattern shown by FIG. 4 ad and FIG. 7 ac.
The stripe patterns of FIGS. 4a to 4d were produced by scribing and stamping, and the island patterns of FIGS. 7a to 7c were fabricated by rolling and stamping.
In addition, the width D of the concave portion of the island pattern, and the length, width, and interval of the convex portion were as shown by the arrows in FIG. 7 a to c.
凹凸模様を片側のみに加工したそれぞれの鋼板について、凹部のピッチを測定するとともに、１０箇所で、直径５ｍｍと２ｍｍの円で囲った範囲内を貫通する凹部の深さ、幅、間隔を調べた。 About each steel plate which processed the concavo-convex pattern only in one side, while measuring the pitch of a crevice, the depth, width, and interval of the crevice which penetrated within the range surrounded by the circle of 5 mm and 2 mm in diameter were examined at ten places. .
次に、凹凸模様を加工した鋼板から、サイズが３０×３０ｍｍの試験片を切り出し、その試験片を２枚重ねてスポット溶接する試験を行った。その際、凹凸模様が加工されていない側の面と、凹凸模様が加工された側の面が、重ね面に来るようにし、その面に油を塗布して重ね合わせた。油には防錆油（パーカー興産株式会社製 NOX-RUST530F(60) ）を使用した。
スポット溶接の際の初期接触部は直径３ｍｍの円形となるように、ナゲット径は４ｍｍとなるように条件を設定した。
Next, a test piece with a size of 30 × 30 mm was cut out from the steel plate processed with the concavo-convex pattern, and the test was performed by overlapping the two test pieces and spot welding. At that time, the surface on which the concavo-convex pattern was not processed and the surface on which the concavo-convex pattern was processed were made to come to the overlapping surface, and oil was applied to the surface for superposition. As the oil, an antirust oil (NOX-RUST 530F (60) manufactured by Parker Kosan Co., Ltd.) was used.
The conditions were set such that the nugget diameter was 4 mm so that the initial contact portion at the time of spot welding had a circular shape with a diameter of 3 mm.
試験片のスポット溶接後、直ちに液体窒素にて冷却した。その後、溶接後の試験片を、ナゲットを含むように１０ｍｍ×１０ｍｍの大きさに切断した。侵入水素量測定は、試験片を昇温することで水素を放出させ、この放出した水素量をガスクロマトグラフによって測定することで行った。昇温速度は１００℃／hour、最高到達温度は２００℃とし、２００℃までに放出された水素量を侵入水素量とした。 Immediately after spot welding of the test piece, it was cooled with liquid nitrogen. Thereafter, the test pieces after welding were cut into a size of 10 mm × 10 mm so as to include nuggets. The amount of intruding hydrogen was measured by releasing hydrogen by raising the temperature of the test piece, and measuring the amount of released hydrogen by gas chromatography. The heating rate was 100 ° C./hour, the maximum temperature reached was 200 ° C., and the amount of hydrogen released up to 200 ° C. was taken as the amount of intruding hydrogen.
結果を表４および表５に示す。
２ｍｍの円で囲った範囲内を貫通する凹部の数が２以上の発明例では、侵入水素量が基準に比べて大幅に減少していた。
これに対し、凹部の数が１の比較例では、侵入水素量が基準に比べて、ほとんど減少しなかった。
The results are shown in Tables 4 and 5.
In the invention examples in which the number of recesses penetrating through the range surrounded by a circle of 2 mm is two or more, the amount of intruding hydrogen was significantly reduced compared to the standard.
On the other hand, in the comparative example in which the number of recesses is 1, the amount of intruding hydrogen was hardly reduced compared to the reference.
１、２ スポット溶接電極 ３、４ 鋼板
５ 鋼板合わせ面 ６ 凹部
７ 凸部 ８ 通路
９ 直径５ｍｍの円 １０ 直径２ｍｍの円
1, 2
Claims (5)
鋼板表面の任意の個所を直径が５ｍｍと２ｍｍの同心円で区切ったとき、前記凹凸模様の凹部によって、前記直径２ｍｍの円内を通り、前記直径５ｍｍの円を貫通して連続する通路が複数形成されており、
該通路は、スポット溶接時に、鋼板合わせ面に存在する油が前記接触部外に出て行く通路となることを特徴とするスポット溶接用鋼板。 It is a steel plate used for spot welding, and a concavo-convex pattern is formed on the surface of the steel plate,
When an arbitrary point on the surface of the steel plate is divided by concentric circles of 5 mm and 2 mm in diameter, a plurality of continuous passages are formed by passing through the circle of 2 mm in diameter and the circle of 5 mm in diameter Has been
A steel plate for spot welding, wherein the passage serves as a passage through which oil present in the steel plate mating surface goes out of the contact portion during spot welding.
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| JPH07284955A (en) * | 1994-04-12 | 1995-10-31 | Toyota Motor Corp | Method for resistance welding plated steel material and aluminum base material and clad material |
| US20050247678A1 (en) * | 2004-05-04 | 2005-11-10 | Pei-Chung Wang | Method of metallurgically bonding articles and article therefor |
| JP2008161878A (en) * | 2006-12-27 | 2008-07-17 | Nippon Steel Corp | Lap resistance spot welding method |
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