JP2010214466A - Method for welding high strength thin steel sheet - Google Patents
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Abstract
Description
本発明は、高強度薄鋼板（特に引張強さ980MPa以上かつ板厚6.0mm以下の高強度薄鋼板）を溶接するにあたって、溶接部の低温割れを抑制し、健全な溶接構造物を得る溶接方法に関するものである。
なお、ここでは溶接金属と溶接熱影響部を総称して溶接部と記す。
The present invention relates to a welding method for obtaining a sound welded structure by suppressing low-temperature cracking in a welded part when welding a high-strength thin steel sheet (particularly a high-strength thin steel sheet having a tensile strength of 980 MPa or more and a thickness of 6.0 mm or less) It is about.
Here, the weld metal and the weld heat affected zone are collectively referred to as a weld zone.
近年、様々な分野で環境の保護や安全性の向上に関する技術が注目されている。たとえば自動車の分野では、地球温暖化の防止を目的として、ＣＯ2の排出量を削減する取組みが進められている。また、衝突時の乗員や歩行者の安全を確保するという社会的要望が高まっている。
自動車の走行によるＣＯ2の排出量を削減するためには、車体の軽量化が多大な効果を発揮する。たとえば車体を100kg軽量化すると、ガソリン１literあたりの走行距離（いわゆる燃費）を約１km／liter向上できる。一方で自動車の安全基準は年々厳しくなっており、車体の強度の向上のみならず強度の最適な配分を達成することによって、乗員および歩行者の安全を確保する技術が求められている。
In recent years, technologies relating to environmental protection and safety improvement have attracted attention in various fields. For example, in the field of automobiles, efforts are being made to reduce CO 2 emissions for the purpose of preventing global warming. In addition, there is a growing social demand to ensure the safety of passengers and pedestrians in the event of a collision.
In order to reduce the amount of CO 2 emitted by driving a car, the weight reduction of the vehicle body has a great effect. For example, if the weight of the vehicle body is reduced by 100 kg, the mileage per 1 liter of gasoline (so-called fuel efficiency) can be improved by about 1 km / liter. On the other hand, the safety standards for automobiles are becoming stricter year by year, and there is a demand for technology for ensuring the safety of passengers and pedestrians by achieving optimal distribution of strength as well as improving the strength of the vehicle body.
多量の薄鋼板を使用して頑丈な車体を製作することで、車体の強度を高めることは可能であるが、軽量化を達成できない。そこで、引張強さを向上した薄鋼板（以下、高強度薄鋼板という）が開発されており、その高強度薄鋼板を用いて車体を製作すれば、車体の強度向上と軽量化を両立させることは可能である。ところが薄鋼板の引張強さが向上すると、薄鋼板を加工してさらに溶接する車体の製作過程で、溶接部の低温割れが発生し易くなるという問題がある。したがって、高強度薄鋼板を用いて製作した車体を実用化するためには、高強度薄鋼板を接合する際の低温割れを抑制する技術を開発する必要がある。 Although it is possible to increase the strength of the vehicle body by manufacturing a sturdy vehicle body using a large amount of thin steel plates, it is not possible to achieve weight reduction. Therefore, thin steel sheets with improved tensile strength (hereinafter referred to as high-strength thin steel sheets) have been developed, and if a vehicle body is manufactured using the high-strength thin steel sheets, it is possible to achieve both strength improvement and weight reduction of the vehicle body. Is possible. However, when the tensile strength of the thin steel plate is improved, there is a problem that cold cracking of the welded portion is likely to occur in the manufacturing process of the vehicle body in which the thin steel plate is processed and further welded. Therefore, in order to put a vehicle body manufactured using a high-strength thin steel plate into practical use, it is necessary to develop a technique for suppressing low-temperature cracking when joining the high-strength thin steel plate.
高強度薄鋼板を得るためには、溶製工程で高強度化元素（たとえばＣ，Si，Mn，Cu，Ni，Cr，Mo，Ｖ，Ｂ等）を添加して圧延工程で圧下量や温度を制御する技術（たとえば特許文献１参照）が知られている。そのような技術を適用して得られる引張強さ780MPa以下の薄鋼板は、溶接による低温割れは生じないので、既に実用化されている。
そして、さらなる圧延技術の進歩によって、980MPa以上の引張強さを有する高強度薄鋼板の製造が可能となってきた。そのような高強度薄鋼板は、溶接による低温割れが発生し易い。特に開先加工を施すことなく、そのまま用いられる板厚6.0mm以下の高強度薄鋼板の１パス溶接では、その傾向が顕著に現われる。溶接した後で熱処理を施すことによって低温割れを抑制することは可能であるが、熱処理によって車体の変形が生じる。しかも極めて大規模な熱処理炉を稼働させる必要があるので、省エネルギーの観点から問題がある。
In order to obtain a high-strength steel sheet, elements for increasing the strength (for example, C, Si, Mn, Cu, Ni, Cr, Mo, V, B, etc.) are added in the melting process, and the rolling amount and temperature are reduced in the rolling process. There is known a technique for controlling (see, for example, Patent Document 1). A thin steel sheet having a tensile strength of 780 MPa or less obtained by applying such a technique does not cause cold cracking due to welding, and has already been put into practical use.
Further, further progress in rolling technology has made it possible to produce high-strength steel sheets having a tensile strength of 980 MPa or more. Such high-strength thin steel sheets are susceptible to cold cracking due to welding. In particular, the tendency appears remarkably in 1-pass welding of a high-strength thin steel plate having a thickness of 6.0 mm or less that is used as it is without performing groove processing. Although it is possible to suppress cold cracking by performing a heat treatment after welding, the heat treatment causes deformation of the vehicle body. Moreover, since it is necessary to operate an extremely large-scale heat treatment furnace, there is a problem from the viewpoint of energy saving.
したがって、引張強さ980MPa以上かつ板厚6.0mm以下の高強度薄鋼板を溶接するにあたって、溶接部の低温割れを抑制する溶接方法を開発する必要がある。 Therefore, it is necessary to develop a welding method that suppresses low-temperature cracking in the welded part when welding a high-strength thin steel sheet having a tensile strength of 980 MPa or more and a thickness of 6.0 mm or less.
本発明は、引張強さ980MPa以上かつ板厚6.0mm以下の高強度薄鋼板を溶接するにあたって、溶接部の低温割れを抑制する溶接方法を提供することを目的とする。 An object of the present invention is to provide a welding method that suppresses low-temperature cracking of a welded part when welding a high-strength thin steel sheet having a tensile strength of 980 MPa or more and a plate thickness of 6.0 mm or less.
発明者らは、引張強さ980MPa以上かつ板厚6.0mm以下の高強度薄鋼板の溶接によって低温割れが発生する原因について調査した。高強度薄鋼板を加工して製造したテスト部材を溶接して溶接部および溶接熱影響部のビッカース硬さを測定したところ、350〜450と著しく高くなっており、溶接部が硬く脆い状態であった。つまり、高強度薄鋼板を加工して複雑な形状の車体用部材を製造することによって加工硬化が生じ、高強度薄鋼板の硬さが大幅に増加した後で溶接を行なうことが低温割れの原因であることが分かった。 The inventors investigated the cause of cold cracking caused by welding of high-strength thin steel sheets having a tensile strength of 980 MPa and a thickness of 6.0 mm or less. When a test member manufactured by processing a high-strength thin steel plate was welded and the Vickers hardness of the welded part and the weld heat affected zone was measured, it was remarkably high at 350 to 450, indicating that the welded part was in a hard and brittle state. It was. In other words, work hardening occurs by processing a high-strength thin steel sheet to produce a car body member with a complicated shape, and welding after the hardness of the high-strength thin steel sheet has greatly increased is the cause of cold cracking. It turns out that.
そこで発明者らは、高強度薄鋼板の溶接による低温割れを抑制する技術について検討した。その結果、高強度薄鋼板を溶接する際に、
(A)溶込み深さを板厚の20％以上とする、
(B)溶接金属のビッカース硬さを270以下とする
ことによって、低温割れを抑制できることが判明した。さらに、
(a)高強度薄鋼板の成分を規定する、
(b)ガスシールドアーク溶接を行なう、
(c)溶接用ワイヤの成分を規定する、
(d)溶接条件を規定する
ことによって、上記の(A)(B)を容易に達成できることが明らかになった。
Therefore, the inventors examined a technique for suppressing low temperature cracking due to welding of a high strength thin steel sheet. As a result, when welding high strength thin steel sheet,
(A) The penetration depth is 20% or more of the plate thickness.
(B) It was found that cold cracking can be suppressed by setting the Vickers hardness of the weld metal to 270 or less. further,
(a) Define the components of the high-strength thin steel sheet,
(b) Perform gas shielded arc welding,
(c) prescribe the components of the welding wire;
(d) It became clear that the above (A) and (B) can be easily achieved by defining the welding conditions.
なお、ここでは一例として自動車の車体について説明したが、本発明は、その他の溶接構造物を製作するための高強度薄鋼板の溶接にも適用できる。
本発明は、これらの知見に基づいてなされたものである。
すなわち本発明は、引張強さ980MPa以上かつ板厚6.0mm以下の高強度薄鋼板の溶接方法において、溶込み深さを板厚の20％以上とし、溶接金属のビッカース硬さを270以下とする高強度薄鋼板の溶接方法である。
In addition, although demonstrated about the vehicle body of the motor vehicle as an example here, this invention is applicable also to the welding of the high strength thin steel plate for manufacturing another welded structure.
The present invention has been made based on these findings.
That is, according to the present invention, in the welding method of a high strength thin steel sheet having a tensile strength of 980 MPa or more and a sheet thickness of 6.0 mm or less, the penetration depth is 20% or more of the sheet thickness, and the Vickers hardness of the weld metal is 270 or less. This is a method for welding high-strength thin steel sheets.
本発明の高強度薄鋼板の溶接方法においては、高強度薄鋼板のＣ含有量を[％Ｃ]（質量％），Si含有量を[％Si]（質量％），Mn含有量を[％Mn]（質量％），Cu含有量を[％Cu]（質量％），Ni含有量を[％Ni]（質量％），Cr含有量を[％Cr]（質量％），Mo含有量を[％Mo]（質量％），Ｖ含有量を[％Ｖ]（質量％），Ｂ含有量を[％Ｂ]（質量％）として、下記の(1)式で算出されるＰcm値を0.245以下とすることが好ましい。このＰcm値は、低温割れ感受性を評価するための炭素当量あり、Ｐcm値が大きいほど低温割れが発生し易いことを示す。 In the high strength steel sheet welding method of the present invention, the C content of the high strength steel sheet is [% C] (mass%), the Si content is [% Si] (mass%), and the Mn content is [%]. Mn] (mass%), Cu content [% Cu] (mass%), Ni content [% Ni] (mass%), Cr content [% Cr] (mass%), Mo content [% Mo] (mass%), V content is [% V] (mass%), B content is [% B] (mass%), Pcm value calculated by the following formula (1) is 0.245 The following is preferable. This Pcm value is a carbon equivalent for evaluating cold cracking susceptibility, and indicates that cold cracking is more likely to occur as the Pcm value increases.
また、高強度薄鋼板を溶接するにあたって、Ｃ含有量が0.10質量％以下，Si含有量が0.95質量％以下，Mn含有量が1.60質量％以下であり、残部がFeおよび不可避的不純物からなる溶接用ワイヤを用い、消耗電極式のガスシールドアーク溶接を行なうことが好ましい。さらに、ガスシールドアーク溶接の溶接電流をＩ（Ａ），アーク電圧をＥ（Ｖ），溶接速度をＳ（mm／秒）とし、高強度薄鋼板の板厚をｔ（mm）として、下記の(2)式で算出されるＱ値を80以上とすることが好ましい。
Ｐcm＝[％Ｃ]＋[％Si]／30＋[％Mn]／20＋[％Cu]／20＋[％Ni]／60＋[％Cr]／20
＋[％Mo]／15＋[％Ｖ]／10＋５[％Ｂ] ・・・(1)
Ｑ＝（Ｉ×Ｅ）／（Ｓ×ｔ2） ・・・(2)
Also, when welding high-strength thin steel sheets, the C content is 0.10% by mass or less, the Si content is 0.95% by mass or less, the Mn content is 1.60% by mass or less, and the balance is Fe and inevitable impurities. It is preferable to perform a consumable electrode type gas shielded arc welding using a working wire. Further, assuming that the welding current of gas shielded arc welding is I (A), the arc voltage is E (V), the welding speed is S (mm / sec), and the plate thickness of the high strength thin steel sheet is t (mm), The Q value calculated by the equation (2) is preferably 80 or more.
Pcm = [% C] + [% Si] / 30 + [% Mn] / 20 + [% Cu] / 20 + [% Ni] / 60 + [% Cr] / 20
+ [% Mo] / 15 + [% V] / 10 + 5 [% B] (1)
Q = (I × E) / (S × t 2 ) (2)
本発明によれば、引張強さ980MPa以上かつ板厚6.0mm以下の高強度薄鋼板を溶接するにあたって、溶接部の低温割れを抑制し、健全な溶接構造物を得ることができる。 According to the present invention, when welding a high-strength thin steel sheet having a tensile strength of 980 MPa or more and a plate thickness of 6.0 mm or less, it is possible to suppress a low-temperature crack in the welded portion and obtain a sound welded structure.
本発明は、引張強さ980MPa以上かつ板厚6.0mm以下の高強度薄鋼板に適用される溶接方法である。
一般に高強度薄鋼板は、Ｃ，Si，Mn，Mo，Ni等を添加して固溶強化を生じさせ、さらにTi，Nb，Ｖ，Ｂ等を添加して析出強化を生じさせるとともに、圧下量や温度を制御しつつ圧延を行なうことによって、引張強さの向上を図っている。このような高強度薄鋼板のうち、引張強さ980MPa以上、特に1180MPa以上、の高強度薄鋼板は、これらの元素の添加量を増加して固溶強化や析出強化を促進する、あるいは過酷な条件で圧延して加工硬化を促進する必要があるので、割れ感受性が増大するのは避けられない。そのため溶接構造物を製作するにあたって、溶接の条件を厳格に管理しなければならない。
The present invention is a welding method applied to a high-strength thin steel plate having a tensile strength of 980 MPa or more and a plate thickness of 6.0 mm or less.
In general, high-strength thin steel sheets are added with C, Si, Mn, Mo, Ni, etc. to cause solid solution strengthening, and Ti, Nb, V, B, etc. are added to cause precipitation strengthening, and the reduction amount Further, the tensile strength is improved by rolling while controlling the temperature. Among these high-strength steel sheets, high-strength steel sheets with a tensile strength of 980 MPa or more, particularly 1180 MPa or more, increase the amount of addition of these elements to promote solid solution strengthening or precipitation strengthening, or severe Since it is necessary to roll under conditions to promote work hardening, it is inevitable that cracking susceptibility increases. Therefore, when manufacturing a welded structure, the welding conditions must be strictly controlled.
ところが本発明の溶接方法を採用すれば、引張強さ980MPa以上の高強度薄鋼板の溶接であっても、容易に低温割れを防止することが可能であり、健全な溶接構造物を安定して製作できる。ただし、高強度薄鋼板の引張強さが1530MPaを超えると、本発明を適用しても溶接による低温割れが発生する惧れがある。したがって、高強度薄鋼板の引張強さは980〜1530MPaの範囲内であることが好ましい。より好ましくは1180〜1380MPaである。 However, if the welding method of the present invention is adopted, it is possible to easily prevent cold cracking even when welding a high-strength thin steel plate having a tensile strength of 980 MPa or more, and a sound welded structure can be stably formed. Can be produced. However, if the tensile strength of the high-strength thin steel sheet exceeds 1530 MPa, cold cracking due to welding may occur even when the present invention is applied. Therefore, the tensile strength of the high-strength thin steel plate is preferably in the range of 980 to 1530 MPa. More preferably, it is 1180-1380 MPa.
また、一般に板厚6.0mm以下の高強度薄鋼板では小入熱で断続的な短い溶接が１層１パスで行なわれるので、溶接部（すなわち溶接金属，溶接熱影響部）の冷却速度が大きくなり、焼入れ効果が発現される。そのため、溶接部が著しく硬化して、低温割れが発生し易くなる。
ところが本発明の溶接方法を採用すれば、板厚6.0mm以下の高強度薄鋼板の溶接であっても、容易に低温割れを防止することが可能であり、健全な溶接構造物を安定して製作できる。ただし、高強度薄鋼板の板厚が1.2mm未満では、溶接によって高張力薄鋼板が溶落ちあるいは変形する惧れがある。したがって、高強度薄鋼板の板厚は1.2〜6.0mmの範囲内であることが好ましい。
In general, high-strength steel sheets with a thickness of 6.0 mm or less perform intermittent short welding with small heat input in one layer and one pass, so the cooling rate of the welded part (ie, weld metal, weld heat affected zone) is high. Thus, a quenching effect is exhibited. Therefore, the welded portion is markedly cured, and low temperature cracking is likely to occur.
However, if the welding method of the present invention is adopted, it is possible to easily prevent low-temperature cracking even when welding a high-strength thin steel plate having a thickness of 6.0 mm or less, and a stable welded structure can be stably formed. Can be produced. However, if the thickness of the high-strength thin steel sheet is less than 1.2 mm, the high-strength thin steel sheet may be melted or deformed by welding. Therefore, the plate thickness of the high-strength thin steel plate is preferably in the range of 1.2 to 6.0 mm.
本発明を適用して高強度薄鋼板の溶接を行なうにあたって、溶込み深さが板厚の20％未満では、形成される溶接金属が少量であるから、溶接部（すなわち溶接金属，溶接熱影響部）の冷却速度が大きくなり、焼入れ効果が生じる。そのため、溶接部が著しく硬化して、低温割れが発生し易くなる。したがって、溶込み深さは板厚の20％以上とする必要がある。好ましくは50％以上である。溶接金属が高強度薄鋼板を貫通して裏波が発生しても問題にならない溶接構造物では、溶込み深さを板厚の100％としても良い。 When welding high-strength thin steel sheets by applying the present invention, if the penetration depth is less than 20% of the plate thickness, a small amount of weld metal is formed. Part) is increased, and a quenching effect is produced. Therefore, the welded portion is markedly cured, and low temperature cracking is likely to occur. Therefore, the penetration depth needs to be 20% or more of the plate thickness. Preferably it is 50% or more. In a welded structure that does not cause a problem even if a weld metal penetrates a high-strength thin steel plate and a back wave is generated, the penetration depth may be 100% of the plate thickness.
本発明では溶接金属の硬さを低く抑えて、溶接構造物の溶接部を高強度薄鋼板よりも軟質にすることによって、溶接部に作用する応力負荷を軽減して、低温割れを抑制する。溶接金属のビッカース硬さが270を超えると、溶接部の硬さが高強度薄鋼板と同等、あるいはそれ以上になるので、溶接部に作用する応力負荷を軽減する効果が得られない。したがって、溶接金属のビッカース硬さは270以下とする。ただし、溶接金属のビッカース硬さが150未満では、高強度薄鋼板を採用した溶接構造物として十分な剛性が得られない。したがって、溶接金属のビッカース硬さは150〜270の範囲内であることが好ましい。より好ましくは150〜250である。 In the present invention, the hardness of the weld metal is kept low and the welded portion of the welded structure is made softer than the high-strength thin steel sheet, thereby reducing the stress load acting on the welded portion and suppressing low-temperature cracking. When the Vickers hardness of the weld metal exceeds 270, the hardness of the welded portion is equal to or higher than that of the high-strength thin steel plate, so that the effect of reducing the stress load acting on the welded portion cannot be obtained. Therefore, the Vickers hardness of the weld metal is 270 or less. However, if the Vickers hardness of the weld metal is less than 150, sufficient rigidity cannot be obtained as a welded structure employing a high strength thin steel plate. Therefore, the Vickers hardness of the weld metal is preferably in the range of 150 to 270. More preferably, it is 150-250.
また本発明では、高強度薄鋼板の成分に基づいて下記の(1)式で算出されるＰcm値が0.245を超えると、溶接部の低温割れが発生し易くなる。したがって、Ｐcm値は0.245以下とすることが好ましい。なお、(1)式中の[％Ｃ]はＣ含有量（質量％），[％Si]はSi含有量（質量％），[％Mn]はMn含有量（質量％），[％Cu]はCu含有量（質量％），[％Ni]はNi含有量（質量％），[％Cr]はCr含有量（質量％），[％Mo]はMo含有量（質量％），[％Ｖ]はＶ含有量（質量％），[％Ｂ]はＢ含有量（質量％）を指す。
Ｐcm＝[％Ｃ]＋[％Si]／30＋[％Mn]／20＋[％Cu]／20＋[％Ni]／60＋[％Cr]／20
＋[％Mo]／15＋[％Ｖ]／10＋５[％Ｂ] ・・・(1)
本発明を適用して高強度薄鋼板を溶接するにあたって使用する溶接用ワイヤは、Ｃを0.10質量％以下，Siを0.95質量％以下，Mnを1.60質量％以下含有することが好ましい。
In the present invention, when the Pcm value calculated by the following formula (1) based on the components of the high-strength thin steel sheet exceeds 0.245, cold cracking of the welded portion is likely to occur. Accordingly, the Pcm value is preferably 0.245 or less. In the formula (1), [% C] is C content (mass%), [% Si] is Si content (mass%), [% Mn] is Mn content (mass%), [% Cu ] Is the Cu content (mass%), [% Ni] is the Ni content (mass%), [% Cr] is the Cr content (mass%), [% Mo] is the Mo content (mass%), [ % V] indicates the V content (mass%), and [% B] indicates the B content (mass%).
Pcm = [% C] + [% Si] / 30 + [% Mn] / 20 + [% Cu] / 20 + [% Ni] / 60 + [% Cr] / 20
+ [% Mo] / 15 + [% V] / 10 + 5 [% B] (1)
It is preferable that the welding wire used in welding the high-strength thin steel sheet by applying the present invention contains C of 0.10% by mass or less, Si of 0.95% by mass or less, and Mn of 1.60% by mass or less.
Ｃは、溶接金属の強度を確保するために重要な固溶強化元素である。本発明では溶接金属のビッカース硬さを270以下に抑えて、溶接構造物の溶接部を高強度薄鋼板よりも軟質にすることによって低温割れを抑制する。ところが溶接用ワイヤのＣ含有量が0.10質量％を超えると、溶接金属のビッカース硬さを270以下に抑えることが困難になる。したがって、溶接用ワイヤのＣ含有量は0.10質量％以下が好ましい。ただし、Ｃ含有量が0.03質量％未満では、溶接金属の強度が不足するので、高強度薄鋼板を採用した溶接構造物として十分な剛性が得られない。したがって、Ｃ含有量は0.03〜0.10質量％の範囲内がより好ましい。 C is a solid solution strengthening element important for securing the strength of the weld metal. In the present invention, the Vickers hardness of the weld metal is suppressed to 270 or less, and the cold cracking is suppressed by making the welded portion of the welded structure softer than the high-strength thin steel plate. However, when the C content of the welding wire exceeds 0.10% by mass, it becomes difficult to suppress the Vickers hardness of the weld metal to 270 or less. Therefore, the C content of the welding wire is preferably 0.10% by mass or less. However, if the C content is less than 0.03% by mass, the strength of the weld metal is insufficient, so that sufficient rigidity cannot be obtained as a welded structure employing a high-strength thin steel plate. Therefore, the C content is more preferably in the range of 0.03 to 0.10% by mass.
Siは、脱酸作用を有する元素であり、溶接金属の脱酸を促進するために不可欠な元素であり、かつ溶接金属の強度を確保するために重要な固溶強化元素である。本発明では溶接金属のビッカース硬さを270以下に抑えて、溶接構造物の溶接部を高強度薄鋼板よりも軟質にすることによって低温割れを抑制する。ところが溶接用ワイヤのSi含有量が0.95質量％を超えると、溶接金属のビッカース硬さを270以下に抑えることが困難になる。したがって、溶接用ワイヤのSi含有量は0.95質量％以下が好ましい。ただし、Si含有量が0.30質量％未満では、溶接金属の脱酸が十分に進行せず、酸化物が溶接金属に混入して種々の欠陥を引き起こす。しかも溶接金属の強度が不足するので、高強度薄鋼板を採用した溶接構造物として十分な剛性が得られない。したがって、Si含有量は0.30〜0.95質量％の範囲内がより好ましい。 Si is an element having a deoxidizing action, is an indispensable element for promoting deoxidation of the weld metal, and is an important solid solution strengthening element for ensuring the strength of the weld metal. In the present invention, the Vickers hardness of the weld metal is suppressed to 270 or less, and the cold cracking is suppressed by making the welded portion of the welded structure softer than the high-strength thin steel plate. However, when the Si content of the welding wire exceeds 0.95 mass%, it becomes difficult to suppress the Vickers hardness of the weld metal to 270 or less. Therefore, the Si content of the welding wire is preferably 0.95% by mass or less. However, when the Si content is less than 0.30% by mass, the deoxidation of the weld metal does not proceed sufficiently, and the oxide is mixed into the weld metal and causes various defects. Moreover, since the strength of the weld metal is insufficient, sufficient rigidity cannot be obtained as a welded structure employing a high-strength thin steel sheet. Therefore, the Si content is more preferably in the range of 0.30 to 0.95 mass%.
Mnは、Siと同様に、脱酸作用を有する元素であり、溶接金属の脱酸を促進するために不可欠な元素であり、かつ溶接金属の強度を確保するために重要な固溶強化元素である。本発明では溶接金属のビッカース硬さを270以下に抑えて、溶接構造物の溶接部を高強度薄鋼板よりも軟質にすることによって低温割れを抑制する。ところが溶接用ワイヤのMn含有量が1.60質量％を超えると、溶接金属のビッカース硬さを270以下に抑えることが困難になる。したがって、溶接用ワイヤのMn含有量は1.60質量％以下が好ましい。ただし、Mn含有量が0.80質量％未満では、溶接金属の脱酸が十分に進行せず、酸化物が溶接金属に混入して種々の欠陥を引き起こす。しかも溶接金属の強度が不足するので、高強度薄鋼板を採用した溶接構造物として十分な剛性が得られない。したがって、Mn含有量は0.80〜1.60質量％の範囲内がより好ましい。 Like Si, Mn is an element having a deoxidizing action, an element indispensable for promoting the deoxidation of the weld metal, and an important solid solution strengthening element for ensuring the strength of the weld metal. is there. In the present invention, the Vickers hardness of the weld metal is suppressed to 270 or less, and the cold cracking is suppressed by making the welded portion of the welded structure softer than the high-strength thin steel plate. However, if the Mn content of the welding wire exceeds 1.60% by mass, it becomes difficult to suppress the Vickers hardness of the weld metal to 270 or less. Therefore, the Mn content of the welding wire is preferably 1.60% by mass or less. However, if the Mn content is less than 0.80% by mass, deoxidation of the weld metal does not proceed sufficiently, and oxides are mixed into the weld metal and cause various defects. Moreover, since the strength of the weld metal is insufficient, sufficient rigidity cannot be obtained as a welded structure employing a high-strength thin steel sheet. Therefore, the Mn content is more preferably in the range of 0.80 to 1.60 mass%.
なお本発明で使用する溶接用ワイヤは、上記した成分に加えて、溶接金属の耐食性，靭性，疲労強度の向上、および溶接する際のアーク安定，スパッタ低減を目的として、Ｐ，Ｓ，Ca，Ti，Zr，Al，Ｋ，Mo，Ｂ，Cr，Ni，Cu，Nb，Ｖ，REM，Se，Te，Biを適宜添加しても良い。
Ｐは、鋼の融点を低下させるとともに、溶接用ワイヤの電気抵抗率を向上させ、溶融効率を高める効果を有し、アークを安定させる作用を有する元素である。ところが溶接用ワイヤのＰ含有量が0.050質量％を超えると、正極性の溶接においては、溶融メタルの粘性が低下し、アークが不安定になるのみならず、小粒のスパッタが増加する。また、溶接金属に高温割れが生じる惧れが高まる。したがって、Ｐは0.050質量％以下が好ましい。
In addition to the above components, the welding wire used in the present invention is made of P, S, Ca, for the purpose of improving the corrosion resistance, toughness and fatigue strength of the weld metal, and stabilizing the arc during welding and reducing spatter. Ti, Zr, Al, K, Mo, B, Cr, Ni, Cu, Nb, V, REM, Se, Te, Bi may be added as appropriate.
P is an element that has the effect of reducing the melting point of steel, improving the electrical resistivity of the welding wire, increasing the melting efficiency, and stabilizing the arc. However, if the P content of the welding wire exceeds 0.050 mass%, in positive polarity welding, the viscosity of the molten metal is reduced, the arc becomes unstable, and small spatter increases. In addition, there is an increased risk of hot cracking in the weld metal. Therefore, P is preferably 0.050% by mass or less.
Ｓは、溶融メタルの粘性を低下させ、溶接用ワイヤの先端に懸垂した溶滴の離脱を促進し、低電流でアークを安定させる作用を有する元素である。また、溶融メタルの粘性を低下させて、ビードを平滑にし、上板の溶落ちを抑制する作用も有する。ところが溶接用ワイヤのＳ含有量が0.050質量％を超えると、小粒のスパッタが増加するのみならず、溶接金属の靭性が低下する。したがって、Ｓは0.050質量％以下が好ましい。 S is an element that acts to lower the viscosity of the molten metal, promote the detachment of the droplet suspended from the tip of the welding wire, and stabilize the arc at a low current. Moreover, it has the effect | action which reduces the viscosity of a molten metal, smoothes a bead, and suppresses the fall of an upper board. However, when the S content of the welding wire exceeds 0.050% by mass, not only small-particle spatter increases but also the toughness of the weld metal decreases. Therefore, S is preferably 0.050% by mass or less.
Caは、溶接用ワイヤの素材となる鋼の製鋼工程や鋳造工程あるいは溶接用ワイヤの伸線工程で不可避的に混入する元素である。溶接用ワイヤのCa含有量が0.0030質量％を超えると、アーク溶接におけるアークの安定性が著しく損なわれる。したがって、Caは0.0030質量％以下が好ましい。
Ti，Zr，Alは、溶融メタルの脱酸剤として溶接用ワイヤに添加する元素であり、溶接金属の強度を高める効果も有する。これらの元素の含有量が合計0.05質量％未満では、溶融メタルの脱酸の効果が十分に得られず、溶融メタルの粘性が向上しない。そのためビード形状の改善効果（すなわち溶接線方向の凹凸の抑制）が得られず、かつ溶接金属の靭性が低下する。一方、これらの元素の含有量が合計0.20質量％を超えると、溶接金属の靭性が大幅に低下する。したがって、Ti，ZrおよびAlのうちの1種または２種以上を合計0.05〜0.20質量％含有することが好ましい。より好ましくは合計0.05〜0.15質量％である。
Ca is an element that is inevitably mixed in the steel making process, the casting process, or the wire drawing process of the welding wire. When the Ca content of the welding wire exceeds 0.0030% by mass, the arc stability in arc welding is significantly impaired. Therefore, Ca is preferably 0.0030% by mass or less.
Ti, Zr, and Al are elements added to the welding wire as a deoxidizer for molten metal, and also have the effect of increasing the strength of the weld metal. When the total content of these elements is less than 0.05% by mass, the effect of deoxidation of the molten metal cannot be sufficiently obtained, and the viscosity of the molten metal is not improved. Therefore, the effect of improving the bead shape (that is, suppressing the unevenness in the weld line direction) cannot be obtained, and the toughness of the weld metal is lowered. On the other hand, when the content of these elements exceeds 0.20 mass% in total, the toughness of the weld metal is significantly lowered. Therefore, it is preferable to contain 0.05 to 0.20 mass% of one or more of Ti, Zr and Al in total. More preferably, it is 0.05-0.15 mass% in total.
Ｋは、アーク溶接におけるアークを広げて、スプレー移行の低電流化を促進し、溶滴を微細化する作用を有する元素である。ところが溶接用ワイヤのＫ含有量が0.0001質量％未満では、その効果は得られない。一方、0.0150質量％を超えると、アークが長くなり、溶接用ワイヤの先端に懸垂した溶滴が不安定になり、スパッタが増加する。したがって、Ｋは0.0001〜0.0150質量％の範囲内が好ましい。より好ましくは0.0003〜0.0030質量％である。 K is an element that has an action of spreading the arc in arc welding, promoting a reduction in spray transfer current, and miniaturizing the droplets. However, when the K content of the welding wire is less than 0.0001% by mass, the effect cannot be obtained. On the other hand, if it exceeds 0.0150% by mass, the arc becomes longer, the droplet suspended at the tip of the welding wire becomes unstable, and spatter increases. Therefore, K is preferably in the range of 0.0001 to 0.0150 mass%. More preferably, it is 0.0003-0.0030 mass%.
また、Ｋは沸点が約760℃と低く、溶接用ワイヤの素材となる鋼の溶製工程でＫを添加しても歩留りが著しく低い。そのため、溶接用ワイヤの製造工程で溶接用ワイヤの表面にカリウム塩溶液を塗布して焼鈍を行なうことによって、溶接用ワイヤの内部にＫを安定して含有させることが好ましい。
Mo，Ｂは、いずれも溶接金属の強度を増加させる作用を有する元素である。ところが、溶接用ワイヤにこれらの元素を過剰に添加すると、溶接金属の靭性が低下する。したがって、Moは0.05〜1.5質量％以下，Ｂは0.0010〜0.020質量％以下の範囲内が好ましい。
Further, K has a low boiling point of about 760 ° C., and even if K is added in the melting process of the steel used as the material for the welding wire, the yield is extremely low. Therefore, it is preferable that K be stably contained in the welding wire by applying a potassium salt solution to the surface of the welding wire and performing annealing in the manufacturing process of the welding wire.
Mo and B are both elements that have the effect of increasing the strength of the weld metal. However, when these elements are excessively added to the welding wire, the toughness of the weld metal is lowered. Therefore, Mo is preferably in the range of 0.05 to 1.5 mass% and B is in the range of 0.0010 to 0.020 mass%.
Cr，Ni，Cuは、いずれも溶接金属の強度を増加させ、かつ耐食性を向上させる作用を有する元素である。ところが、溶接用ワイヤにこれらの元素を過剰に添加すると、溶接金属の靭性が低下する。したがって、Crは3.0質量％以下，Niは3.0質量％以下，Cuは3.0質量％以下が好ましい。
Nb，Ｖは、いずれも溶接金属の強度，靭性を向上し、かつアークの安定性を向上する作用を有する元素である。ところが、溶接用ワイヤにこれらの元素を過剰に添加すると、溶接金属の靭性が低下する。したがって、Nbは0.05質量％以下，Ｖは0.05質量％以下が好ましい。
Cr, Ni, and Cu are all elements that have the effect of increasing the strength of the weld metal and improving the corrosion resistance. However, when these elements are excessively added to the welding wire, the toughness of the weld metal is lowered. Therefore, Cr is preferably 3.0% by mass or less, Ni is 3.0% by mass or less, and Cu is preferably 3.0% by mass or less.
Nb and V are elements that have the effect of improving the strength and toughness of the weld metal and improving the stability of the arc. However, when these elements are excessively added to the welding wire, the toughness of the weld metal is lowered. Therefore, Nb is preferably 0.05% by mass or less and V is preferably 0.05% by mass or less.
本発明で使用する溶接用ワイヤの上記した成分以外の残部は、Feおよび不可避的不純物である。不可避的不純物としては、Ｏ：0.030質量％以下，Ｎ：0.020質量％以下が許容できる。
なおＯは、溶接用ワイヤの素材となる鋼の溶製工程あるいは溶接用ワイヤの製造工程で不可避的に混入する元素である。しかし、溶滴の移行形態を微細化する効果を有しているので、Ｏ含有量は0.0020質量％以上とするのが好ましい。また、過剰な含有は溶接金属の強度向上と靭性の劣化を招くことからＯ含有量は0.030質量％以下が好ましい。0.0080質量％以下が一層好ましい。よって、溶接用ワイヤのＯ含有量は0.0020〜0.030質量％の範囲内が好ましい。より好ましくは0.0030〜0.0080質量％である。
The balance other than the above-described components of the welding wire used in the present invention is Fe and inevitable impurities. As unavoidable impurities, O: 0.030 mass% or less and N: 0.020 mass% or less are acceptable.
Note that O is an element that is inevitably mixed in the melting process of the steel used as the material of the welding wire or the manufacturing process of the welding wire. However, the O content is preferably 0.0020% by mass or more because it has the effect of miniaturizing the droplet transfer form. Moreover, since excessive inclusion causes the strength improvement and deterioration of toughness of a weld metal, O content is preferably 0.030% by mass or less. 0.0080 mass% or less is still more preferable. Therefore, the O content of the welding wire is preferably in the range of 0.0020 to 0.030 mass%. More preferably, it is 0.0030-0.0080 mass%.
本発明では、上記の成分を有する溶接用ワイヤを用いて、ガスシールドアーク溶接を行なうことが好ましい。その理由は、溶接用ワイヤに含有されるＣ，Si，Mnの酸化や窒化がシールドガスによって防止され、各元素がその効果を発揮するからである。さらに、ガスシールドアーク溶接を逆極性（すなわち溶接用ワイヤをプラス極）で行なうことが好ましい。その理由は、Si−Mn系溶接用ワイヤと通常の装置を用いた低電流の溶接において、アークが安定し、深い溶込みが得られるからである。 In the present invention, it is preferable to perform gas shielded arc welding using a welding wire having the above components. The reason is that oxidation, nitridation of C, Si, and Mn contained in the welding wire is prevented by the shielding gas, and each element exhibits its effect. Furthermore, it is preferable to perform the gas shielded arc welding with the reverse polarity (that is, the welding wire is a plus electrode). The reason is that the arc is stabilized and deep penetration is obtained in low current welding using a Si-Mn welding wire and a normal apparatus.
ガスシールドアーク溶接を行なう際に、その設定条件に基づいて下記の(2)式で算出されるＱ値が80を超えると、溶接部の低温割れが発生し易くなる。したがって、Ｑ値は80以下とすることが好ましい。なお、(2)式中のＩはガスシールドアーク溶接の溶接電流（Ａ），Ｅはアーク電圧（Ｖ），Ｓは溶接速度（mm／秒）を指し、ｔは高強度薄鋼板の板厚（mm）を指す。
Ｑ＝（Ｉ×Ｅ）／（Ｓ×ｔ2） ・・・(2)
When performing gas shielded arc welding, if the Q value calculated by the following equation (2) based on the setting conditions exceeds 80, cold cracking of the welded portion is likely to occur. Therefore, the Q value is preferably 80 or less. In equation (2), I is the welding current (A) for gas shielded arc welding, E is the arc voltage (V), S is the welding speed (mm / sec), and t is the thickness of the high strength steel sheet. (Mm)
Q = (I × E) / (S × t 2 ) (2)
板厚1.6mmの高強度薄鋼板とワイヤ径1.2mmの溶接用ワイヤを用いてガスシールドアーク溶接法による隅肉溶接の溶接試験を行なった。その溶接試験の手順と結果を以下に説明する。
使用した高強度薄鋼板の成分および引張強さは表１に示す通りである。溶接用ワイヤの成分は表２に示す通りである。なお、溶接用ワイヤの表面には厚さ0.5μｍのCuめっきを施し、さらに潤滑油を塗布した。潤滑油は鉱物油を使用し、その塗布量は溶接用ワイヤ10kg当たり１ｇとした。
Welding tests of fillet welding by gas shielded arc welding were performed using a high strength thin steel plate with a thickness of 1.6 mm and a welding wire with a wire diameter of 1.2 mm. The welding test procedure and results will be described below.
The components and tensile strength of the high-strength thin steel plates used are as shown in Table 1. The components of the welding wire are as shown in Table 2. The surface of the welding wire was plated with Cu having a thickness of 0.5 μm, and further lubricating oil was applied. The lubricating oil used was mineral oil, and the amount applied was 1 g per 10 kg of welding wire.
高強度薄鋼板（板厚1.6mm）から幅45mm，長さ90mmの溶接試験片を切り出した。さらに図１に示すように、２枚の溶接試験片1a，1bを重ね代20mmで重ね合わせて、拘束板２の中央部に全周溶接で固定して試験体を作成した。拘束板２は、板厚25mm，幅150mm，長さ250mmの厚鋼板を使用した。各試験体ごとに隅肉溶接を２回ずつ（溶接長さ20mm／回）行なった。その際、各試験体の第１回の隅肉溶接を行ない、その後６時間空冷して、その隅肉溶接部3aが室温まで冷却された後に第２回の隅肉溶接を行なった。このようにして第１回の隅肉溶接部3aの残熱が第２回の隅肉溶接部3bの特性に影響を及ぼすのを防止した。
A weld specimen of 45 mm in width and 90 mm in length was cut out from a high-strength thin steel plate (plate thickness 1.6 mm). Further, as shown in FIG. 1, two
試験体に供した溶接試験片（鋼板記号Ｐ１〜Ｐ４）と隅肉溶接で使用した溶接用ワイヤ（ワイヤ記号Ｗ１〜Ｗ４）の組合せは、表３に示す通りである。各組合せ（溶接番号１〜13）ごとに５個ずつ試験体を作成して合計10回の隅肉溶接を行なった。隅肉溶接は逆極性のガスシールドアーク溶接法で行ない、その溶接電流，アーク電圧，溶接速度，入熱は表３に示す通りである。なお、シールドガスはAr−20％ＣＯ2ガスを使用し、突き出し長さ15mm，トーチ角45°とした。 Table 3 shows the combinations of the weld specimens (steel plate symbols P1 to P4) used for the specimen and the welding wires (wire symbols W1 to W4) used in fillet welding. Five specimens were prepared for each combination (welding numbers 1 to 13), and a total of 10 fillet welds were performed. Fillet welding is performed by gas shielded arc welding with a reverse polarity. The welding current, arc voltage, welding speed, and heat input are as shown in Table 3. The shielding gas used was Ar-20% CO 2 gas, the protruding length was 15 mm, and the torch angle was 45 °.
隅肉溶接が終了した後、隅肉溶接部3a，3bを室温まで空冷し、得られた溶接ビードの中央部の断面をマクロ観察して、溶込み深さを測定し、さらに溶接金属や溶接熱影響部における低温割れの有無を調査した。また、溶接金属のビッカース硬さを測定した。その結果を表３に併せて示す。なお、表３に示す溶込み深さ（％）は、溶接試験片1a，1b（すなわち高強度薄鋼板）の板厚（mm）に対する溶接金属の最大深さ（mm）の比率である。また低温割れについては、10個の溶接ビードのいずれにも低温割れが認められなかったものを優（○），１〜２個の溶接ビードにて低温割れが認められたものを良（△），３個以上の溶接ビードにて低温割れが認められたものを不可（×）として評価した。
After fillet welding is completed, the fillet welds 3a and 3b are air-cooled to room temperature, the cross section of the center of the resulting weld bead is macro-observed, the penetration depth is measured, and the weld metal and weld The presence or absence of cold cracking in the heat affected zone was investigated. Further, the Vickers hardness of the weld metal was measured. The results are also shown in Table 3. The penetration depth (%) shown in Table 3 is the ratio of the maximum depth (mm) of the weld metal to the thickness (mm) of the
表３に示す発明例（すなわち溶接番号１〜11）は、溶接金属のビッカース硬さと溶込み深さが本発明の範囲を満足する例である。比較例のうち、溶接番号12は溶接金属のビッカース硬さが本発明の範囲を外れる例，溶接番号13は溶込み深さが本発明の範囲を外れる例である。
表３から明らかなように、発明例（すなわち溶接番号１〜11）では低温割れが大幅に低減された。
The invention examples shown in Table 3 (that is, welding numbers 1 to 11) are examples in which the Vickers hardness and penetration depth of the weld metal satisfy the scope of the present invention. Among the comparative examples, weld number 12 is an example in which the Vickers hardness of the weld metal is outside the scope of the present invention, and weld number 13 is an example in which the penetration depth is outside the scope of the present invention.
As is apparent from Table 3, cold cracking was significantly reduced in the inventive examples (that is, welding numbers 1 to 11).
引張強さ980MPa以上の高張力薄鋼板を溶接するにあたって、溶接部の低温割れを抑制し、健全な溶接構造物を得ることができるので、産業上格段の効果を奏する。 When welding a high-strength thin steel sheet with a tensile strength of 980 MPa or more, it is possible to obtain a sound welded structure by suppressing low-temperature cracking of the welded portion, so that there is a remarkable industrial effect.
1a 溶接試験片
1b 溶接試験片
２ 拘束板
3a 隅肉溶接部
3b 隅肉溶接部
1a Weld specimen
3a Fillet weld
3b Fillet weld
Claims (4)
Ｐcm＝[％Ｃ]＋[％Si]／30＋[％Mn]／20＋[％Cu]／20＋[％Ni]／60＋[％Cr]／20
＋[％Mo]／15＋[％Ｖ]／10＋５[％Ｂ] ・・・(1)
[％Ｃ]：Ｃ含有量（質量％）
[％Si]：Si含有量（質量％）
[％Mn]：Mn含有量（質量％）
[％Cu]：Cu含有量（質量％）
[％Ni]：Ni含有量（質量％）
[％Cr]：Cr含有量（質量％）
[％Mo]：Mo含有量（質量％）
[％Ｖ]：Ｖ含有量（質量％）
[％Ｂ]：Ｂ含有量（質量％） The C content of the high-strength thin steel sheet is [% C], the Si content is [% Si], the Mn content is [% Mn], the Cu content is [% Cu], and the Ni content is [% Ni]. Pcm value calculated by the following formula (1) where Cr content is [% Cr], Mo content is [% Mo], V content is [% V], and B content is [% B]. The method for welding a high-strength thin steel sheet according to claim 1, wherein the thickness is 0.245 or less.
Pcm = [% C] + [% Si] / 30 + [% Mn] / 20 + [% Cu] / 20 + [% Ni] / 60 + [% Cr] / 20
+ [% Mo] / 15 + [% V] / 10 + 5 [% B] (1)
[% C]: C content (% by mass)
[% Si]: Si content (% by mass)
[% Mn]: Mn content (% by mass)
[% Cu]: Cu content (% by mass)
[% Ni]: Ni content (% by mass)
[% Cr]: Cr content (mass%)
[% Mo]: Mo content (mass%)
[% V]: V content (mass%)
[% B]: B content (mass%)
Ｑ＝（Ｉ×Ｅ）／（Ｓ×ｔ2） ・・・(2)
Ｉ：溶接電流（Ａ）
Ｅ：アーク電圧（Ｖ）
Ｓ：溶接速度（mm／秒）
ｔ：高強度薄鋼板の板厚（mm）
When performing the gas shielded arc welding, the welding current is I, the arc voltage is E, the welding speed is S, the plate thickness of the high-strength steel sheet is t, and the Q value calculated by the following equation (2) is The method for welding high-strength thin steel sheet according to claim 3, wherein the welding method is 80 or more.
Q = (I × E) / (S × t 2 ) (2)
I: Welding current (A)
E: Arc voltage (V)
S: Welding speed (mm / sec)
t: Thickness of high strength steel sheet (mm)
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| WO2018159719A1 (en) * | 2017-02-28 | 2018-09-07 | 新日鐵住金株式会社 | Fillet welded joint and manufacturing method thereof |
| CN112008206A (en) * | 2020-07-09 | 2020-12-01 | 华电电力科学研究院有限公司 | Welding method for quenched and tempered high-strength steel plate |
| CN114769804A (en) * | 2022-02-28 | 2022-07-22 | 南京钢铁股份有限公司 | Gas shielded welding method for 890-grade ultrahigh-strength marine board |
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| WO2018159719A1 (en) * | 2017-02-28 | 2018-09-07 | 新日鐵住金株式会社 | Fillet welded joint and manufacturing method thereof |
| JP6432716B1 (en) * | 2017-02-28 | 2018-12-05 | 新日鐵住金株式会社 | Fillet welded joint and manufacturing method thereof |
| CN110382154A (en) * | 2017-02-28 | 2019-10-25 | 日本制铁株式会社 | Fillet-welded joint and its manufacturing method |
| CN110382154B (en) * | 2017-02-28 | 2021-06-22 | 日本制铁株式会社 | Fillet welded joint and method for manufacturing same |
| US11235415B2 (en) | 2017-02-28 | 2022-02-01 | Nippon Steel Corporation | Fillet welded joint and method of manufacturing thereof |
| CN112008206A (en) * | 2020-07-09 | 2020-12-01 | 华电电力科学研究院有限公司 | Welding method for quenched and tempered high-strength steel plate |
| CN114769804A (en) * | 2022-02-28 | 2022-07-22 | 南京钢铁股份有限公司 | Gas shielded welding method for 890-grade ultrahigh-strength marine board |
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