JP6434387B2 - Low hydrogen coated arc welding rod - Google Patents
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本発明は、低水素系被覆アーク溶接棒に関し、特に直流電源を用いた多層盛溶接において、溶接作業性が良好であり、溶接のまま（以下、ＡＷという。）及び溶接後熱処理（溶接熱影響部の軟化、溶接部の靱性改善及び溶接残留応力の除去を目的に行われる熱処理：以下、ＰＷＨＴという。）後の溶接金属の強度に優れ、低温での靱性も優れる低水素系被覆アーク溶接棒に関するものである。 The present invention relates to a low hydrogen-based coated arc welding rod, and particularly, in multi-layer welding using a DC power source, welding workability is good, as-welded (hereinafter referred to as AW) and heat treatment after welding (welding heat influence). Heat treatment performed for the purpose of softening the weld, improving the toughness of the weld and removing the residual welding stress: hereinafter referred to as PWHT.) Low hydrogen-coated arc welding rod with excellent weld metal strength and excellent toughness at low temperatures It is about.
低水素系被覆アーク溶接棒は、耐割れ性や低温靱性が優れていることから、拘束が強い箇所や高張力鋼の溶接に広く使用されている。一方、最近の溶接構造物の大型化にともない、使用鋼材の高強度化が要望されている。また、天然資源の開発を目的とした大型海洋構造物や球形タンク等では、安全性の確保のため、低温での靱性値の更なる向上や、ＰＷＨＴ後の機械的性能確保が重要となる。しかし、一般に溶接金属の強度増加と低温靱性確保は相反する傾向を示すため、高強度化とともに低温靱性を向上させる新たな手法が必要とされている。 Low hydrogen-based coated arc welding rods are widely used for welding highly constrained parts and high-strength steel because of their excellent crack resistance and low-temperature toughness. On the other hand, with the recent increase in size of welded structures, it is desired to increase the strength of steel used. In large-scale offshore structures and spherical tanks for the purpose of developing natural resources, it is important to further improve the toughness value at low temperatures and ensure mechanical performance after PWHT in order to ensure safety. However, in general, increasing the strength of weld metal and ensuring low temperature toughness tend to conflict with each other, and therefore, a new method for increasing strength and improving low temperature toughness is required.
また、低水素系被覆アーク溶接棒の溶接電源は、交流電源と直流電源に分類されるが、球形タンクや海洋構造物の現場溶接では、直流電源が使用されることが多い。この直流電源用の被覆アーク溶接棒は、その溶接環境から溶接金属中に窒素や酸素などを巻き込みやすいので、溶接欠陥が発生することがあり、所望の機械性能を満足できないという問題がある。即ち、直流電源用の被覆アーク溶接棒においては、従来より溶接金属の性能に関する要望が強い。 In addition, welding power sources for low hydrogen-based coated arc welding rods are classified into AC power sources and DC power sources, but DC power sources are often used in field welding of spherical tanks and offshore structures. Since this coated arc welding rod for DC power supply tends to involve nitrogen, oxygen or the like in the weld metal from its welding environment, there is a problem that welding defects may occur and desired mechanical performance cannot be satisfied. That is, in the coated arc welding rod for DC power supply, there is a strong demand for the performance of the weld metal.
このような低水素系被覆アーク溶接棒をめぐる状況の中で、溶接金属の低温での機械的性能の向上として、例えば特許文献１には、低温靱性と破壊靱性（以下、ＣＴＯＤという。）値が優れた溶接金属を得ることを目的とした低水素系被覆アーク溶接棒に関する技術の開示がある。しかし、特許文献１に記載の技術は、交流電源を用いた溶接を前提としており、また、直流電源を用いた場合には溶接金属が５９０ＭＰａ以上の強度を満足しない。 In the situation of such a low hydrogen-based coated arc welding rod, for example, Patent Document 1 discloses low temperature toughness and fracture toughness (hereinafter referred to as CTOD) as an improvement in mechanical performance of weld metal at low temperatures. There is a disclosure of a technique related to a low hydrogen based arc welding rod for the purpose of obtaining an excellent weld metal. However, the technique described in Patent Document 1 is premised on welding using an AC power source, and when a DC power source is used, the weld metal does not satisfy the strength of 590 MPa or more.
また、特許文献２の開示技術には、被覆剤中のＣｒ、Ｍｏ、Ｓｉ等の各成分の含有比率を適量とすることで、直流電源を用いた溶接においてＣＴＯＤ値が優れた溶接金属を得ることができる被覆アーク溶接棒の技術の開示がある。しかし、特許文献２に記載の技術は、ＰＷＨＴ後において優れた溶接金属の強度及び低温靭性を得ることができないという問題点がある。 In addition, the disclosed technique of Patent Document 2 obtains a weld metal having an excellent CTOD value in welding using a DC power source by setting the content ratio of each component such as Cr, Mo, Si, etc. in the coating material to an appropriate amount. There are disclosures of techniques for coated arc welding rods that can be used. However, the technique described in Patent Document 2 has a problem that it is impossible to obtain excellent weld metal strength and low-temperature toughness after PWHT.
一方、特許文献３には、Ｎｉを添加し、かつ、ＭｎとＮｉの合計を限定することによって、低温靱性を向上させる被覆アーク溶接棒の技術が開示されている。しかし、直流電源の使用時の溶接作業性やＰＷＨＴ後における溶接金属の機械的性能については特段考慮されていない。 On the other hand, Patent Document 3 discloses a technique of a coated arc welding rod that improves low temperature toughness by adding Ni and limiting the total of Mn and Ni. However, no special consideration is given to the welding workability when using a DC power supply or the mechanical performance of the weld metal after PWHT.
本発明は、上述した問題点に鑑みてなされたものであって、直流電源を用いた多層盛溶接において、溶接作業性が良好であり、かつ、ＡＷ及びＰＷＨＴ後の溶接金属の強度及び低温での靱性が優れる５９０ＭＰａ級高張力鋼用の低水素系被覆アーク溶接棒を提供することを目的とする。 The present invention has been made in view of the above-described problems, and in multi-layer welding using a DC power source, welding workability is good, and the strength and low temperature of the weld metal after AW and PWHT are low. An object of the present invention is to provide a low hydrogen-based coated arc welding rod for 590 MPa class high strength steel having excellent toughness.
本発明者らは、低水素系被覆アーク溶接棒を使用し、直流電源を用いた５９０ＭＰａ級高張力鋼の溶接において、溶接作業性が良好で、ＡＷ及びＰＷＨＴ後の強度及び低温靱性に優れる溶接金属が得られ、かつ、ＰＷＨＴ後の強度の低下を抑えることが可能な低水素系被覆アーク溶接棒の成分組成について種々検討した。 The present inventors use a low-hydrogen-based coated arc welding rod, and in welding of a 590 MPa class high-strength steel using a DC power source, welding workability is good, and welding with excellent strength and low-temperature toughness after AW and PWHT. Various investigations were made on the composition of the components of the low hydrogen-based coated arc welding rod that can obtain a metal and that can suppress a decrease in strength after PWHT.
その結果、溶接棒中のＡｌ及びＭｇを適正量とすることで、強脱酸剤として作用させるとともに、金属炭酸塩を適正量とすることで、溶接金属中の酸素を低減し、溶接金属の低温靱性を向上させることができることを突き止めた。 As a result, by making the amount of Al and Mg in the welding rod appropriate, it acts as a strong deoxidizer, and by making the metal carbonate an appropriate amount, the oxygen in the weld metal is reduced, It has been found that low temperature toughness can be improved.
また、溶接棒中のＭｎ及びＭｏを適正量とすることで、ＡＷ及びＰＷＨＴ後の溶接金属の強度を確保し、かつ、Ｎｉ、Ｔｉ及びＢを適正量とすることで溶接金属の低温靭性を向上させることができることを突き止めた。 In addition, by making Mn and Mo in the welding rods appropriate, the strength of the weld metal after AW and PWHT is ensured, and by making Ni, Ti and B proper, the low temperature toughness of the weld metal is ensured. I found out that it can be improved.
さらに、金属炭酸塩、金属弗化物、Ｓｉ酸化物及びＴｉ酸化物を適正量とすることで、スラグ被包性、スラグ剥離性及びビード形状を良好にするとともに、Ｓｉ、Ｎａ化合物及びＫ化合物を適正量とし、軟鋼心線への被覆剤の被覆率を適正とすることで、アーク状態を良好にできることを突き止めた。 Furthermore, by making metal carbonate, metal fluoride, Si oxide and Ti oxide in proper amounts, slag encapsulation, slag peelability and bead shape are improved, and Si, Na compound and K compound are added. It was found out that the arc state can be improved by setting an appropriate amount and an appropriate coating rate of the coating on the mild steel core wire.
すなわち、本発明の要旨は、軟鋼心線に被覆剤が塗布されている低水素系被覆アーク溶接棒において、被覆剤全質量に対する質量％で、金属炭酸塩の１種または２種以上の合計：４０〜５８％、金属弗化物の１種または２種以上の合計：１０〜２０％、Ｓｉ酸化物のＳｉＯ2換算値：４〜１０％、Ｔｉ酸化物のＴｉＯ2換算値：２〜６％、Ｓｉ：２〜５％、Ｍｎ：２〜６％、Ｎｉ：４〜８％、Ｔｉ：０．５〜２．５％、Ｍｏ：０．２〜０．８％、Ａｌ：０．６〜１．６％、Ｍｇ：０．４〜１．４％、Ｂ合金及びＢ化合物のＢ換算値の１種または２種以上の合計：０．０５〜０．３５％、Ｎａ化合物のＮａ2Ｏ換算値とＫ化合物のＫ2Ｏ換算値の合計：２〜５％を含有し、残部はスラグ形成剤、塗装剤としてのアルギン酸ソーダ、マイカの１種以上の合計：５％以下、鉄粉、鉄合金からのＦｅ分及び不可避不純物からなる被覆剤を前記軟鋼心線の外周に当該低水素系被覆アーク溶接棒全質量に対する質量％で２８〜４０％の被覆率で塗布したことを特徴とする低水素系被覆アーク溶接棒。 That is, the gist of the present invention is a low hydrogen-based arc welding rod in which a coating agent is applied to a mild steel core wire, in a mass% with respect to the total mass of the coating agent, and a total of one or more metal carbonates: 40 to 58%, one or more of the total metal fluorides: 10 to 20% SiO 2 converted value of Si oxide: 4 to 10% TiO 2 converted value of Ti oxides: 2-6% Si: 2-5%, Mn: 2-6%, Ni: 4-8%, Ti: 0.5-2.5%, Mo: 0.2-0.8%, Al: 0.6- 1.6%, Mg: 0.4 to 1.4%, total of one or more of B conversion values of B alloy and B compound: 0.05 to 0.35%, Na 2 O of Na compound total K 2 O conversion value converted value and K compound: containing 2-5%, the remainder being the slag forming agents, sodium alginate as a coating agent, 1 mica more kinds Total above: 5% or less , 28 to 40% by mass% with respect to the total mass of the low hydrogen-based coated arc welding rod on the outer periphery of the mild steel core wire with a coating consisting of iron powder, Fe content from iron alloy and inevitable impurities A low hydrogen-based coated arc welding rod characterized by being applied at a coating rate of
本発明を適用した低水素系被覆アーク溶接棒によれば、直流電源を用いた多層盛溶接において、溶接作業性が良好であり、ＡＷ及びＰＷＨＴ後においても高強度の溶接金属が得られると共に低温での安定した靱性が得られる。したがって、各種鋼構造物に対する溶接継手の信頼性を大幅に向上させることができる。 According to the low hydrogen-based coated arc welding rod to which the present invention is applied, welding workability is good in multi-layer welding using a DC power source, and a high-strength weld metal can be obtained even after AW and PWHT and at low temperature. Stable toughness can be obtained. Therefore, the reliability of the welded joint for various steel structures can be greatly improved.
以下、本発明における低水素系被覆アーク溶接棒について詳細に説明をする。本発明を適用した低水素系被覆アーク溶接棒軟鋼心線に被覆剤を塗布させてなるものである。この被覆剤中の各成分組成の限定理由について詳細に説明する。なお、低水素系被覆アーク溶接棒の各成分組成における含有率は、被覆剤全質量に対する質量％で表すこととし、以下では単に％と記載する。 Hereinafter, the low hydrogen-based coated arc welding rod in the present invention will be described in detail. The present invention is applied to a low hydrogen-based coated arc welding rod mild steel core wire with a coating agent. The reasons for limiting the composition of each component in the coating will be described in detail. In addition, the content rate in each component composition of a low hydrogen type | system | group covering arc welding rod shall be represented by the mass% with respect to the coating-material total mass, and is only described as% below.
［金属炭酸塩の１種または２種以上の合計：４０〜５８％］
金属炭酸塩は、ＣａＣＯ3、ＭｇＣＯ3、ＢａＣＯ3などを指し、アークの熱で分解してＣＯ2ガスを発生し、溶接金属を大気から保護するシールド効果としての働きがある。金属炭酸塩の１種または２種以上の合計が４０％未満では、上述したシールド効果が不足し、ブローホールが発生してしまう。また、溶接金属中に大気中の窒素が混入し、ＡＷ及びＰＷＨＴ後の低温靱性が低下する。一方、金属炭酸塩の１種または２種以上の合計が５８％を超えると、アークが不安定でビード形状が凸状になり、スラグ剥離性も悪くなる。従って、金属炭酸塩の１種または２種以上の合計は４０〜５８％とする。
[Total of one or more metal carbonates: 40 to 58%]
Metal carbonate refers to CaCO 3 , MgCO 3 , BaCO 3, etc., and functions as a shield effect that decomposes with the heat of the arc to generate CO 2 gas and protects the weld metal from the atmosphere. When the total of one or more of the metal carbonates is less than 40%, the shielding effect described above is insufficient and blow holes are generated. Moreover, nitrogen in the atmosphere is mixed into the weld metal, and the low temperature toughness after AW and PWHT is lowered. On the other hand, if the total of one or more of the metal carbonates exceeds 58%, the arc becomes unstable, the bead shape becomes convex, and the slag releasability also deteriorates. Therefore, the total of one or more metal carbonates is 40 to 58%.
［金属弗化物の１種または２種以上の合計：１０〜２０％］
金属弗化物は、ＣａＦ2、ＭｇＦ2、ＡｌＦ3などを指し、溶融スラグの流動性を調整してスラグ被包性を改善してビード外観を良好にするために添加する。金属弗化物の１種または２種以上の合計が１０％未満では、溶融スラグの流動性が悪いため、スラグ被包性が悪く、ビード外観が不良になる。一方、金属弗化物の１種または２種以上の合計が２０％を超えると、被覆筒の形状が不完全となって片溶け状態となり、アークが不安定となる。従って、金属弗化物の１種または２種以上の合計は１０〜２０％とする。
[Total of one or more metal fluorides: 10 to 20%]
Metal fluoride refers to CaF 2 , MgF 2 , AlF 3, etc., and is added to adjust the fluidity of the molten slag to improve the slag encapsulation and improve the bead appearance. If the total of one or more of the metal fluorides is less than 10%, the flowability of the molten slag is poor, so the slag encapsulation is poor and the bead appearance is poor. On the other hand, if the total of one or more of the metal fluorides exceeds 20%, the shape of the coated cylinder becomes incomplete, the piece is melted, and the arc becomes unstable. Therefore, the total of one or more metal fluorides is 10 to 20%.
［Ｓｉ酸化物のＳｉＯ2換算値：４〜１０％］
Ｓｉ酸化物を構成するＳｉＯ2は、珪砂、長石、水ガラス等から添加され、溶融スラグの粘性を高め、適切な粘性のスラグを確保してビード形状を良好にし、溶接作業性を改善する。Ｓｉ酸化物のＳｉＯ2換算値が４％未満では、スラグの粘性が低くなり、ビード形状が不良となる。一方、Ｓｉ酸化物のＳｉＯ2換算が１０％を超えると、スラグがガラス状になり、スラグ剥離性が不良になる。従って、Ｓｉ酸化物のＳｉＯ2換算値は４~１０％とする。
[Si oxide converted to SiO 2 : 4 to 10%]
SiO 2 constituting the Si oxide is added from silica sand, feldspar, water glass, and the like to increase the viscosity of the molten slag, ensure a suitable viscosity slag, improve the bead shape, and improve welding workability. When the SiO 2 equivalent value of the Si oxide is less than 4%, the viscosity of the slag becomes low and the bead shape becomes poor. On the other hand, when the SiO 2 in terms of Si oxide is more than 10%, the slag is glassy, slag removability becomes poor. Therefore, the SiO 2 equivalent value of Si oxide is 4 to 10%.
［Ｔｉ酸化物のＴｉＯ2換算値：２〜６％］
Ｔｉ酸化物を構成するＴｉＯ2は、ルチール、酸化チタン、チタン酸ソーダ、チタンスラグ等から添加され、アークを安定にし、スラグの粘性を調整してビード形状を良好にする。Ｔｉ酸化物のＴｉＯ2換算値が２％未満であると、アークが不安定となり、良好なビードを得られない。一方、Ｔｉ酸化物のＴｉＯ2換算値が６％を超えると、溶融スラグの粘性が高くなってスラグの流動性が悪くなるので、ビード形状が凸状となる。従って、Ｔｉ酸化物のＴｉＯ2換算値は２~６％とする。
[TiO 2 converted value of Ti oxides: 2-6%]
TiO 2 constituting the Ti oxide is added from rutile, titanium oxide, sodium titanate, titanium slag, etc., stabilizes the arc, and adjusts the viscosity of the slag to improve the bead shape. When the TiO 2 conversion value of the Ti oxide is less than 2%, the arc becomes unstable and a good bead cannot be obtained. On the other hand, if the TiO 2 equivalent value of the Ti oxide exceeds 6%, the viscosity of the molten slag increases and the fluidity of the slag deteriorates, so that the bead shape becomes convex. Therefore, the TiO 2 equivalent value of the Ti oxide is 2 to 6%.
［Ｓｉ：２〜５％］
Ｓｉは、金属Ｓｉ、Ｆｅ−Ｓｉ、Ｆｅ−Ｓｉ−Ｍｎ等から添加され、溶接金属の脱酸を目的として使用されるとともに、溶接作業性の確保の面からも必要である。Ｓｉが２％未満では、脱酸不足で溶接金属中にブローホールなどの気孔が発生しやすく、また、アークが不安定となる。一方、Ｓｉが５％を超えると、粒界に低融点酸化物を析出させ、ＡＷ及びＰＷＨＴ後の溶接金属の低温靱性が低下する。従って、Ｓｉは２〜５％とする。
[Si: 2 to 5%]
Si is added from metals Si, Fe-Si, Fe-Si-Mn, etc., and is used for the purpose of deoxidizing the weld metal, and is also necessary from the viewpoint of ensuring the workability of welding. When Si is less than 2%, pores such as blow holes are easily generated in the weld metal due to insufficient deoxidation, and the arc becomes unstable. On the other hand, when Si exceeds 5%, a low melting point oxide is precipitated at the grain boundary, and the low temperature toughness of the weld metal after AW and PWHT is lowered. Therefore, Si is 2 to 5%.
［Ｍｎ：２〜６％］
Ｍｎは、金属Ｍｎ、Ｆｅ−Ｍｎ、Ｆｅ−Ｓｉ−Ｍｎ等から添加され、Ｓｉと同様に脱酸剤として重要であり、溶接金属組織を微細化させ、溶接金属の低温靱性及び強度を高める。またＭｎは、焼入れ性が強いことから、ＰＷＨＴ後の強度確保にも有効である。Ｍｎが２％未満では、ＡＷ及びＰＷＨＴ後の溶接金属の強度及び低温靭性が低下する。またＭｎが２％未満では、脱酸不足となって溶接金属中にブローホールが発生しやすくなる。一方、Ｍｎが６％を超えると、溶接金属の強度が過剰に高くなり、低温靭性が低下する。またＭｎが６％を超えると、焼入れ性が強く作用し、ＰＷＨＴ後の溶接金属の強度が高くなって靱性が低下する。従って、Ｍｎは２〜６％とする。
[Mn: 2 to 6%]
Mn is added from metals Mn, Fe-Mn, Fe-Si-Mn, etc., and is important as a deoxidizer like Si, refines the weld metal structure, and increases the low-temperature toughness and strength of the weld metal. Mn is also effective in securing strength after PWHT because of its strong hardenability. If Mn is less than 2%, the strength and low temperature toughness of the weld metal after AW and PWHT are lowered. On the other hand, if Mn is less than 2%, deoxidation is insufficient and blow holes are likely to occur in the weld metal. On the other hand, if Mn exceeds 6%, the strength of the weld metal becomes excessively high, and the low-temperature toughness decreases. If Mn exceeds 6%, the hardenability acts strongly, the strength of the weld metal after PWHT increases, and the toughness decreases. Therefore, Mn is 2 to 6%.
［Ｎｉ：４〜８％］
Ｎｉは、金属Ｎｉから添加され、溶接金属の強度及び低温靭性を向上させる元素である。Ｎｉが４％未満では、ＡＷ及びＰＷＨＴ後の必要な溶接金属の強度及び低温靭性を確保することができない。一方、Ｎｉが８％を超えると、溶接金属の強度が過剰に高くなり、ＡＷにおける低温靭性が低下する。また、ＰＷＨＴ後の溶接金属の低温靭性も低下する。従って、Ｎｉは４〜８％とする。
[Ni: 4-8%]
Ni is an element which is added from the metal Ni and improves the strength and low temperature toughness of the weld metal. If Ni is less than 4%, the required weld metal strength and low temperature toughness after AW and PWHT cannot be secured. On the other hand, if Ni exceeds 8%, the strength of the weld metal becomes excessively high, and the low-temperature toughness in AW decreases. Moreover, the low temperature toughness of the weld metal after PWHT is also reduced. Therefore, Ni is 4 to 8%.
［Ｔｉ：０．５〜２．５％］
Ｔｉは、金属Ｔｉ、Ｆｅ−Ｔｉ等から添加され、脱酸剤として有効であると同時に、アークの電位傾度を低下させてアークを安定化させる。またＴｉは、溶接金属のミクロ組織を微細化して低温靭性を向上させる働きがある。Ｔｉが０．５％未満では、アークが不安定となり、アーク長が伸びて大気中の酸素を取り込みやすくなるので、溶接金属中に酸素量が多くなるとともに、溶接金属のミクロ組織が微細化されず、ＡＷ及びＰＷＨＴ後の溶接金属の低温靭性が低下する。一方、Ｔｉが２．５％を超えると、溶接金属中のＴｉ酸化物の析出が増加し、ＡＷ及びＰＷＨＴ後の溶接金属の低温靱性が低下する。従って、Ｔｉは０．５〜２．５％とする。
[Ti: 0.5 to 2.5%]
Ti is added from metals Ti, Fe-Ti, and the like, and is effective as a deoxidizer, and at the same time reduces the potential gradient of the arc and stabilizes the arc. Ti also works to refine the microstructure of the weld metal and improve low temperature toughness. If Ti is less than 0.5%, the arc becomes unstable, and the arc length increases and it becomes easy to take in oxygen in the atmosphere. Therefore, the amount of oxygen in the weld metal increases, and the microstructure of the weld metal is refined. However, the low temperature toughness of the weld metal after AW and PWHT is reduced. On the other hand, when Ti exceeds 2.5%, precipitation of Ti oxide in the weld metal increases, and the low temperature toughness of the weld metal after AW and PWHT decreases. Therefore, Ti is 0.5 to 2.5%.
［Ｍｏ：０．２〜０．８％］
Ｍｏは、金属Ｍｏ、Ｆｅ−Ｍｏ等から添加され、溶接金属の強度を向上させる元素である。またＭｏは、焼入れ性が強いことから、ＰＷＨＴ後の強度確保にも有効である。Ｍｏが０．２％未満では、ＡＷ及びＰＷＨＴ後の必要な溶接金属の強度を確保することができない。一方、Ｍｏが０．８％を超えると、ＡＷ及びＰＷＨＴ後の溶接金属の強度が過剰に高くなり、低温靭性が低下する。従って、Ｍｏは０．２〜０．８％とする。
[Mo: 0.2 to 0.8%]
Mo is an element that is added from metal Mo, Fe—Mo, or the like and improves the strength of the weld metal. Mo is also effective in securing strength after PWHT because it has a strong hardenability. If Mo is less than 0.2%, the required weld metal strength after AW and PWHT cannot be ensured. On the other hand, if Mo exceeds 0.8%, the strength of the weld metal after AW and PWHT becomes excessively high, and the low-temperature toughness decreases. Therefore, Mo is 0.2 to 0.8%.
［Ａｌ：０．６〜１．６％］
Ａｌは、金属Ａｌ、Ｆｅ−Ａｌ、Ａｌ−Ｍｇ等から添加され、溶接金属の脱酸を目的として使用される。Ａｌが０．６％未満では、脱酸不足で溶接金属中にブローホールなどの気孔が発生しやすくなる。一方、Ａｌが１．６％を超えると、脱酸生成物のＡｌ2Ｏ3が溶接金属中に残存して酸素量を増加させるので、ＡＷ及びＰＷＨＴ後の溶接金属の低温靱性が低下する。従って、Ａｌは０．６〜１．６％とする。
[Al: 0.6 to 1.6%]
Al is added from metal Al, Fe—Al, Al—Mg, or the like, and is used for the purpose of deoxidizing the weld metal. If Al is less than 0.6%, deoxidation is insufficient and pores such as blow holes are likely to occur in the weld metal. On the other hand, when Al exceeds 1.6%, Al 2 O 3 as a deoxidation product remains in the weld metal and increases the amount of oxygen, so that the low temperature toughness of the weld metal after AW and PWHT decreases. Therefore, Al is made 0.6 to 1.6%.
［Ｍｇ：０．４〜１．４％］
Ｍｇは、金属Ｍｇ、Ａｌ−Ｍｇ等から添加され、他の合金成分よりも脱酸効果が高く、溶接金属中の酸素量を低減させることができる。Ｍｇが０．４％未満であると、溶接金属の酸素量が多くなって、ＡＷ及びＰＷＨＴ後の溶接金属の低温靱性が低下する。一方、Ｍｇが１．４％を超えると、アークの広がりが劣化して不安定となり、ビード形状が不良になる。従って、Ｍｇは０．４〜１．４％とする。
[Mg: 0.4 to 1.4%]
Mg is added from metal Mg, Al—Mg, or the like, has a higher deoxidation effect than other alloy components, and can reduce the amount of oxygen in the weld metal. If Mg is less than 0.4%, the oxygen content of the weld metal increases, and the low-temperature toughness of the weld metal after AW and PWHT decreases. On the other hand, if Mg exceeds 1.4%, the spread of the arc deteriorates and becomes unstable, and the bead shape becomes poor. Therefore, Mg is 0.4 to 1.4%.
［Ｂ合金及びＢ化合物のＢ換算値の１種または２種以上の合計：０．０５〜０．３５％］
Ｂは、金属Ｂ、Ｆｅ−Ｂ、Ｆｅ−Ｍｎ−Ｂ、硼砂、硼酸ナトリウム等のＢ合金やＢ化合物から添加され、極微量で焼入れ性を向上させて粒界フェライトの生成抑制に有効な元素で、溶接金属の低温靭性の向上に有効である。Ｂ合金及びＢ化合物のＢ換算値の１種または２種以上の合計が０．０５％未満では、Ｂによる粒界フェライトの抑制効果が働かず、フェライト粒が粗大になりやすく、溶接金属の金属組織が粗くなり、ＡＷ及びＰＷＨＴ後の溶接金属の低温靱性が低下する。一方、Ｂ合金及びＢ化合物のＢ換算値の１種または２種以上の合計が０．３５％を超えると、溶接金属が粗大なラス状組織になり、ＡＷ及びＰＷＨＴ後の溶接金属の低温靭性が低下する。従って、Ｂ合金及びＢ化合物のＢ換算値の１種または２種以上の合計は０．０５〜０．３５％とする。
[Total of one or two or more B conversion values of B alloy and B compound: 0.05 to 0.35%]
B is an element that is added from metals B, Fe-B, Fe-Mn-B, B alloys such as borax and sodium borate and B compounds, and is effective in suppressing the formation of intergranular ferrite by improving the hardenability in a very small amount. Therefore, it is effective for improving the low temperature toughness of the weld metal. If the total of one or more of B conversion values of B alloy and B compound is less than 0.05%, the effect of suppressing grain boundary ferrite by B does not work, and ferrite grains tend to become coarse, and the metal of the weld metal The structure becomes rough and the low temperature toughness of the weld metal after AW and PWHT is reduced. On the other hand, if the total of one or more of B conversion values of B alloy and B compound exceeds 0.35%, the weld metal becomes a coarse lath structure, and the low temperature toughness of the weld metal after AW and PWHT Decreases. Therefore, the total of one or more of the B converted values of the B alloy and the B compound is 0.05 to 0.35%.
［Ｎａ化合物のＮａ2Ｏ換算値とＫ化合物のＫ2Ｏ換算値の合計：２〜５％］
Ｎａ2Ｏ及びＫ2Ｏは、珪酸ソーダや珪酸カリウム等の水ガラスから主に添加され、溶接棒製造時の塗装性及び溶接時のアークの安定性を向上する効果がある。また、カリ長石、弗化ソーダ、硼酸ナトリウムからも添加され、溶接作業性確保の上からも必要である。Ｎａ化合物のＮａ2Ｏ換算値とＫ化合物のＫ2Ｏ換算値の合計が２％未満では、アークが不安定になる。また、生産時の塗装性が劣化し、溶接棒製造時に被覆剤表面に割れが生じやすくなり、溶接棒の生産性が低下する。一方、Ｎａ化合物のＮａ2Ｏ換算値とＫ化合物のＫ2Ｏ換算値の合計が５％を超えると、アークの吹き付けが強くなり、スパッタ発生量が多くなる。従って、Ｎａ化合物のＮａ2Ｏ換算値とＫ化合物のＫ2Ｏ換算値の合計は２〜５％とする。
Total of K 2 O conversion value of terms of Na 2 O values and K compounds of Na compounds: 2-5%]
Na 2 O and K 2 O are mainly added from water glass such as sodium silicate and potassium silicate, and have an effect of improving paintability at the time of manufacturing a welding rod and arc stability at the time of welding. In addition, potassium feldspar, sodium fluoride, and sodium borate are also added, which is necessary for ensuring welding workability. The total is less than 2% of K 2 O conversion value of terms of Na 2 O values and K compounds of Na compounds, arc becomes unstable. Moreover, the coating property at the time of production deteriorates, and the surface of the coating material is easily cracked during the production of the welding rod, so that the productivity of the welding rod is lowered. On the other hand, the sum of K 2 O conversion value of terms of Na 2 O values and K compounds of Na compound is more than 5%, blowing of the arc is intensified, it becomes large spatter. Thus, a total of K 2 O conversion value of terms of Na 2 O values and K compounds of Na compound to 2-5%.
なお、本発明の低水素系被覆アーク溶接棒の被覆剤の残部は、スラグ形成剤、塗装剤、鉄粉、鉄合金からのＦｅ分及び不可避不純物である。スラグ形成剤は、酸化マグネシウム等が用いられ、１種以上の合計で７％以下が好ましい。塗装剤は、アルギン酸ソーダ、マイカ等が用いられ、１種以上を合計で５％以下が好ましい。不可避不純物は特に限定しないが、耐割れ性の観点から、Ｐは０．０１０％以下、Ｓは０．０１０％以下が好ましい。 In addition, the remainder of the coating material of the low hydrogen-based coated arc welding rod of the present invention is a slag forming agent, a coating agent, iron powder, Fe content from iron alloy and inevitable impurities. Magnesium oxide or the like is used as the slag forming agent, and the total of one or more is preferably 7% or less. As the coating agent, sodium alginate, mica and the like are used, and one or more kinds are preferably 5% or less in total. The inevitable impurities are not particularly limited, but from the viewpoint of crack resistance, P is preferably 0.010% or less, and S is preferably 0.010% or less.
[被覆剤の軟鋼心線の外周への被覆率:低水素系被覆アーク溶接棒全質量に対する質量％で２８〜４０％]
被覆剤の軟鋼心線の外周への被覆率は、被覆剤の片溶けや、スラグ状態に大きく影響する。被覆剤の被覆率が低水素家被覆アーク溶接棒全質量に対する質量％（以下、単に％という。）で２８％未満では、軟鋼心線の周囲に塗装された被覆自体が脆くなるため、片溶けが発生しやすくなる。一方、被覆剤の被覆率が４０％を超えると、スラグ量が過多となり、アークが不安定になる。したがって、軟鋼心線の軟鋼心線への被覆率は２８〜４０％とする。
[Coating ratio of coating material on outer circumference of mild steel core wire: 28-40% by mass% with respect to the total mass of low hydrogen-based coated arc welding rod]
The coverage of the coating material on the outer periphery of the mild steel core wire greatly affects the melting of the coating material and the slag state. If the coating rate of the coating material is less than 28% by mass (hereinafter simply referred to as%) with respect to the total mass of the low-hydrogen housed arc welding rod, the coating itself coated around the mild steel core wire becomes brittle, so Is likely to occur. On the other hand, when the coating rate of the coating agent exceeds 40%, the amount of slag becomes excessive and the arc becomes unstable. Therefore, the coverage of the mild steel core wire to the mild steel core wire is 28 to 40%.
使用する軟鋼心線は、ＪＩＳ Ｇ３５２３ ＳＷＹ１１を用いることが好ましいが、軟鋼心線中のＣの含有量は、軟鋼心線の全質量に対する質量％で０．０５〜０．０８％が好ましい。このＣの含有量は、強度を調整するために被覆剤からも適正に調整できる。軟鋼心線のＰは靭性を劣化するので軟鋼心線の全質量に対する質量％で０．０１０％以下、Ｓはスラグの流動性を悪化させるので軟鋼心線の全質量に対する質量％で０．０１０％以下、ＮはＢとの結合力が強く焼き入れ性を劣化させるので軟鋼心線の全質量に対する質量％で０．００５％以下であることが好ましい。 Although the JIS G3523 SWY11 is preferably used as the mild steel core to be used, the content of C in the mild steel core is preferably 0.05 to 0.08% by mass% with respect to the total mass of the mild steel core. The C content can be appropriately adjusted from the coating material in order to adjust the strength. Since P in the mild steel core deteriorates toughness, it is 0.010% or less in terms of mass% with respect to the total mass of the mild steel core, and S deteriorates the fluidity of slag, so that 0.010 in mass% with respect to the total mass of the mild steel core. %, N has a strong bonding force with B and deteriorates the hardenability, so that it is preferably 0.005% or less in terms of mass% with respect to the total mass of the mild steel core wire.
以下、本発明を適用した低水素系被覆アーク溶接棒の実施例について具体的に説明する。 Hereinafter, the Example of the low hydrogen type | system | group covering arc welding rod to which this invention is applied is described concretely.
直径４．０ｍｍ、長さ４００ｍｍのＪＩＳ Ｇ３５２３ ＳＷＹ１１の軟鋼心線（Ｃ:０．０８質量％、Ｓｉ:０．０１質量％、Ｍｎ:０．４８質量％、Ｐ:０．００９質量％、Ｓ:０．００５質量％、Ｎ：０．００２３質量％）の外周に、表１に示す成分組成の被覆剤を表１に示す被覆率で塗装した後、乾燥させて各種低水素系被覆アーク溶接棒を試作した。 JIS G3523 SWY11 soft steel core wire having a diameter of 4.0 mm and a length of 400 mm (C: 0.08 mass%, Si: 0.01 mass%, Mn: 0.48 mass%, P: 0.009 mass%, S : 0.005% by mass, N: 0.0023% by mass) The coating composition having the composition shown in Table 1 was coated at the coverage shown in Table 1, and then dried to provide various low hydrogen-based coated arc welding. Produced a stick.
上記の各種試作溶接棒を用い、表２に示す成分の板厚４８ｍｍの鋼板をＸ開先（表側：３０ｍｍ深さ、開先角度：５０°、ギャップ２ｍｍ、ルート部：２ｍｍ、裏側：２５ｍｍ深さまで裏はつり、開先角度６０°）とし、アーク溶接を行った。電源は直流電源を使用し、溶接電流１４０Ａ、溶接入熱２５ｋＪ／ｃｍ、予熱・パス間温度１００〜１５０℃、立向姿勢で溶接継手を作製した。 Using the above-mentioned various prototype welding rods, a steel plate having a thickness of 48 mm having the components shown in Table 2 is X groove (front side: 30 mm depth, groove angle: 50 °, gap 2 mm, root portion: 2 mm, back side: 25 mm depth The back was suspended and the groove angle was 60 °), and arc welding was performed. A DC power source was used as a power source, and a welded joint was produced with a welding current of 140 A, a welding heat input of 25 kJ / cm, a preheating / pass temperature of 100 to 150 ° C., and a vertical posture.
上記溶接の際、各溶接棒の溶接作業性を調査した。溶接終了後、ＪＩＳＺ ３１０４に準じてＸ線透過試験を行い、溶接欠陥の有無を調査した。また、溶接金属試験は、ＡＷの溶接金属及びＰＷＨＴ後の溶接金属を評価対象とした。ＰＷＨＴは、温度５８０℃、保持時間が４．５時間の条件で行った。各試験板の表側２ｍｍ下の溶接金属よりＪＩＳ Ｚ２２４２ Ｖノッチ衝撃試験片、１５ｍｍ下の溶接金属よりＪＩＳ Ｚ２２４１ １０号引張試験片を採取した。引張試験は、引張強さが６１０〜７３０ＭＰａを良好、靱性の評価は、試験温度−５０℃でシャルピー衝撃試験を実施し、吸収エネルギーの３回の平均値が７０Ｊ以上を良好とした。それらの試験結果を表３にまとめて示す。 During the above welding, the welding workability of each welding rod was investigated. After the end of welding, an X-ray transmission test was conducted according to JISZ 3104 to investigate the presence or absence of welding defects. In the weld metal test, AW weld metal and weld metal after PWHT were evaluated. PWHT was performed under conditions of a temperature of 580 ° C. and a holding time of 4.5 hours. A JIS Z2242 V-notch impact test piece was taken from the weld metal 2 mm below the front side of each test plate, and a JIS Z2241 No. 10 tensile test piece was taken from the weld metal 15 mm below. In the tensile test, the tensile strength was from 610 to 730 MPa, and the toughness was evaluated by conducting a Charpy impact test at a test temperature of −50 ° C., and the average value of three absorbed energy values was 70 J or more. The test results are summarized in Table 3.
表１及び表３中溶接棒Ｎｏ．１〜Ｎｏ．１０が本発明例、溶接棒Ｎｏ．１１〜Ｎｏ．２３は比較例である。本発明例であるＮｏ．１〜Ｎｏ．１０は、被覆剤の金属炭酸塩の合計、金属弗化物の合計、ＳｉＯ2換算値、ＴｉＯ2換算値、Ｓｉ、Ｍｎ、Ｎｉ、Ｔｉ、Ｍｏ、Ａｌ、Ｍｇ、Ｂ及びＢ換算値の合計、Ｎａ2Ｏ換算値とＫ2Ｏ換算値の合計、被覆率がいずれも本発明において規定した範囲内にあるので、溶接作業性が良好で、溶接欠陥も無く、ＡＷ及びＰＷＨＴ後の溶接金属の引張強さ及び吸収エネルギーが共に良好であり、極めて満足な結果であった。 In Table 1 and Table 3, the welding rod No. 1-No. 10 is an example of the present invention, welding rod No. 11-No. 23 is a comparative example. No. which is an example of the present invention. 1-No. 10 is the total of the metal carbonate of the coating, the total of the metal fluoride, the SiO 2 equivalent value, the TiO 2 equivalent value, the sum of the Si, Mn, Ni, Ti, Mo, Al, Mg, B and B equivalent values, Since the total of Na 2 O converted value and K 2 O converted value and the coverage are both within the range defined in the present invention, the welding workability is good, there is no welding defect, and the weld metal after AW and PWHT Both the tensile strength and the absorbed energy were good, and the results were very satisfactory.
比較例中溶接棒Ｎｏ．１１は、金属弗化物が少ないので、スラグ被包性が不良で、ビード外観も不良であった。また、Ｓｉが多いので、ＡＷ及びＰＷＨＴ後の溶接金属の吸収エネルギーが低かった。 In the comparative example, the welding rod No. No. 11 had less metal fluoride, so the slag encapsulation was poor and the bead appearance was also poor. Moreover, since there is much Si, the absorbed energy of the weld metal after AW and PWHT was low.
溶接棒Ｎｏ．１２は、ＳｉＯ2換算値が少ないので、ビード形状が不良であった。また、Ｍｎが多いので、ＡＷ及びＰＷＨＴ後の溶接金属の引張強さが高く、吸収エネルギーが低かった。 Welding rod no. No. 12 had a poor bead shape because of its small SiO 2 conversion value. Moreover, since there was much Mn, the tensile strength of the weld metal after AW and PWHT was high, and the absorbed energy was low.
溶接棒Ｎｏ．１３は、ＴｉＯ2換算値が少ないので、アークが不安定となり、ビード形状が不良であった。また、Ｎｉが多いので、ＡＷの溶接金属の引張強さが高く、またＡＷ及びＰＷＨＴ後の溶接金属の吸収エネルギーが低かった。さらに、Ａｌが少ないので、溶接金属中にブローホールが発生した。 Welding rod no. In No. 13, since the TiO 2 conversion value was small, the arc became unstable and the bead shape was poor. Moreover, since there is much Ni, the tensile strength of the weld metal of AW was high, and the absorbed energy of the weld metal after AW and PWHT was low. Further, since there is little Al, blowholes were generated in the weld metal.
溶接棒Ｎｏ．１４は、Ｔｉが多いので、ＡＷ及びＰＷＨＴ後の溶接金属の吸収エネルギーが低かった。また、Ｎａ2Ｏ換算値とＫ2Ｏ換算値の合計が多いので、アークの吹き付けが強く、スパッタ発生量が多かった。 Welding rod no. Since No. 14 had a lot of Ti, the absorbed energy of the weld metal after AW and PWHT was low. Further, since the terms of Na 2 O values and K sum is often the 2 O converted value, blowing of the arc is strong, the amount of occurrence of spatter was large.
溶接棒Ｎｏ．１５は、ＴｉＯ2換算値が多いので、ビード形状が凸状で不良であった。また、Ｍｏが多いので、ＡＷ及びＰＷＨＴ後の溶接金属の引張強さが高く、吸収エネルギーが低かった。さらに、被覆率が高いので、アークが不安定であった。 Welding rod no. No. 15 had a poor bead shape due to its large TiO 2 conversion value. Moreover, since there is much Mo, the tensile strength of the weld metal after AW and PWHT was high, and the absorbed energy was low. Furthermore, since the coverage was high, the arc was unstable.
溶接棒Ｎｏ．１６は、ＳｉＯ2換算値が多いので、スラグ剥離性が不良であった。また、Ａｌが多いので、ＡＷ及びＰＷＨＴ後の溶接金属の吸収エネルギーが低かった。 Welding rod no. 16, since the SiO 2 converted value is large, the slag removability was poor. Moreover, since there is much Al, the absorbed energy of the weld metal after AW and PWHT was low.
溶接棒Ｎｏ．１７は、Ｎｉが少ないので、ＡＷ及びＰＷＨＴ後の溶接金属の引張強さ及び吸収エネルギーが低かった。また、Ｍｇが多いので、アークの広がりが少なく不安定で、ビード形状が不良となった。 Welding rod no. No. 17 had low Ni, so the tensile strength and absorbed energy of the weld metal after AW and PWHT were low. Moreover, since there was much Mg, the spread of the arc was small and unstable, and the bead shape was poor.
溶接棒Ｎｏ．１８は、Ｓｉが少ないので、アークが不安定で、溶接金属中にブローホールが発生した。また、Ｂ及びＢ換算値の合計が多いので、ＡＷ及びＰＷＨＴ後の溶接金属の吸収エネルギーが低かった。 Welding rod no. No. 18 had less Si, so the arc was unstable, and blow holes were generated in the weld metal. Further, since the total of B and B converted values is large, the absorbed energy of the weld metal after AW and PWHT was low.
溶接棒Ｎｏ．１９は、Ｍｎが少ないので、ＡＷ及びＰＷＨＴ後の溶接金属の引張強さ及び吸収エネルギーが低かった。また、溶接金属中にブローホールが発生した。さらに、Ｎａ2Ｏ換算値とＫ2Ｏ換算値の合計が少ないので、アークが不安定であった。 Welding rod no. No. 19 had low Mn, so the tensile strength and absorbed energy of the weld metal after AW and PWHT were low. In addition, blow holes occurred in the weld metal. Furthermore, since the total of Na 2 O converted value and K 2 O converted value was small, the arc was unstable.
溶接棒Ｎｏ．２０は、Ｔｉが少ないので、アークが不安定で、ＡＷ及びＰＷＨＴ後の溶接金属の吸収エネルギーが低かった。また、Ｍｏが少ないので、ＡＷ及びＰＷＨＴ後の溶接金属の引張強さが低かった。 Welding rod no. No. 20 had less Ti, so the arc was unstable, and the absorbed energy of the weld metal after AW and PWHT was low. Moreover, since there is little Mo, the tensile strength of the weld metal after AW and PWHT was low.
溶接棒Ｎｏ．２１は、金属弗化物が多いので、アークが不安定で、被覆筒が片溶け状態であった。また、Ｂ及びＢ換算値の合計が少ないので、ＡＷ及びＰＷＨＴ後の溶接金属の吸収エネルギーが低かった。 Welding rod no. No. 21 had a large amount of metal fluoride, so that the arc was unstable, and the coated cylinder was in a state of being partially melted. Moreover, since the total of B and B conversion value is small, the absorbed energy of the weld metal after AW and PWHT was low.
溶接棒Ｎｏ．２２は、金属炭酸塩が多いので、アークが不安定で、ビード形状が凸状になり、スラグ剥離性も不良であった。また、Ｍｇが少ないので、ＡＷ及びＰＷＨＴ後の溶接金属の吸収エネルギーが低かった。 Welding rod no. No. 22 had a large amount of metal carbonate, so the arc was unstable, the bead shape became convex, and the slag peelability was poor. Moreover, since there was little Mg, the absorbed energy of the weld metal after AW and PWHT was low.
溶接棒Ｎｏ．２３は、金属炭酸塩が少ないので、ＡＷ及びＰＷＨＴ後の溶接金属の吸収エネルギーが低かった。また、溶接金属中にブローホールが発生した。さらに、被覆率が低いので、被覆筒が片溶け状態であった。 Welding rod no. No. 23 had less metal carbonate, so the absorbed energy of the weld metal after AW and PWHT was low. In addition, blow holes occurred in the weld metal. Furthermore, since the coverage was low, the coated cylinder was in a state of being melted in one piece.
Claims (1)
被覆剤全質量に対する質量％で、
金属炭酸塩の１種または２種以上の合計：４０〜５８％、
金属弗化物の１種または２種以上の合計：１０〜２０％、
Ｓｉ酸化物のＳｉＯ2換算値：４〜１０％、
Ｔｉ酸化物のＴｉＯ2換算値：２〜６％、
Ｓｉ：２〜５％、
Ｍｎ：２〜６％、
Ｎｉ：４〜８％、
Ｔｉ：０．５〜２．５％、
Ｍｏ：０．２〜０．８％、
Ａｌ：０．６〜１．６％、
Ｍｇ：０．４〜１．４％、
Ｂ合金及びＢ化合物のＢ換算値の１種または２種以上の合計：０．０５〜０．３５％、
Ｎａ化合物のＮａ2Ｏ換算値とＫ化合物のＫ2Ｏ換算値の合計：２〜５％を含有し、
残部はスラグ形成剤、塗装剤としてのアルギン酸ソーダ、マイカの１種以上の合計：５％以下、鉄粉、鉄合金からのＦｅ分及び不可避不純物からなる被覆剤を前記軟鋼心線の外周に当該低水素系被覆アーク溶接棒全質量に対する質量％で２８〜４０％の被覆率で塗布したことを特徴とする低水素系被覆アーク溶接棒。 In a low hydrogen-based coated arc welding rod with a coating applied to a mild steel core wire,
In mass% with respect to the total mass of the coating agent,
Total of one or more metal carbonates: 40-58%,
Total of one or more metal fluorides: 10 to 20%,
SiO 2 conversion value of Si oxide: 4 to 10%,
TiO 2 conversion value of Ti oxide: 2 to 6%,
Si: 2 to 5%,
Mn: 2-6%
Ni: 4-8%,
Ti: 0.5 to 2.5%,
Mo: 0.2 to 0.8%,
Al: 0.6 to 1.6%,
Mg: 0.4 to 1.4%,
Total of one or more of B conversion values of B alloy and B compound: 0.05 to 0.35%,
Total K 2 O conversion value of terms of Na 2 O values and K compounds of Na compound: containing 2-5%,
The remainder is a slag forming agent, sodium alginate as a coating agent, and a total of one or more of mica: 5% or less , a coating agent comprising iron powder, Fe content from iron alloy and unavoidable impurities on the outer periphery of the mild steel core wire A low hydrogen-based coated arc welding rod characterized by being applied at a coating rate of 28 to 40% by mass% with respect to the total mass of the low hydrogen-based coated arc welding rod.
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