JP3747729B2 - Ni-base alloy coated arc welding rod - Google Patents
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Description
【０００１】
【産業上の利用分野】
この発明は、耐食性、特に耐硫酸腐食性に優れたＮｉ基合金を溶接するためのＮｉ基合金被覆アーク溶接棒に関するものであり、また、耐食性、特に耐硫酸腐食性に優れたライニングを肉盛溶接により形成するためのＮｉ基合金被覆アーク肉盛溶接棒に関するものである。
【０００２】
【従来の技術】
例えば、火力発電所においては、ボイラーにＢ、Ｃ重油または石炭などを燃やして純水を加熱し、高温水蒸気を作製し、この高温水蒸気を利用して蒸気タービンを回して発電している。このボイラーで発生した燃焼ガスは、まず脱硝装置により脱硝処理されたのち、空気予熱器に送って燃焼用空気を加熱し、さらに脱硫装置にて脱硫処理し、ついで煙突から大気中に放出される。前記脱硝装置によりＮＯx が除去された燃焼ガスは、空気予熱器に送られ、そこで燃焼用空気を予熱することにより１５０〜２５０℃に冷却され、さらに脱硫装置を通ることにより１５０℃未満（通常は約８０℃）に冷却された後、煙突から放出される。
【０００３】
脱硝装置により脱硝処理された燃焼ガスは、その温度が２５０℃以下に下がるが、その成分は空気以外にＣＯx 、ＳＯx を多く含み、その他ＨＣｌ、脱硝されなかった微量のＮＯx の他、装置から発生するＦｅ3+イオンを含み、さらには未燃焼炭素のススやダストなどの固形浮遊物を含むといわれている。この脱硝装置を通過した燃焼ガスは１５０℃に程度に冷却されると水蒸気とＳＯ3 が反応してＨ2 ＳＯ4 となって結露し、８０％前後の濃硫酸が生成する。この結露した硫酸にはＨＣｌ、ＮＯx 、Ｏ2 、ＣＯx を始めとする腐食性ガスおよび酸化性イオンのＦｅ3+を含み、さらにススの本体である微細な炭素やダストが含まれている。
【０００４】
かかる多様な腐食因子が含まれている結露した硫酸は特に腐食性が強く、この結露した硫酸による腐食を「硫酸露点腐食」という。水蒸気とＳＯ3 が反応してＨ2 ＳＯ4 となって結露する量は１１０〜１３０℃の温度範囲で最大となるところから、この温度範囲で金属材料の硫酸露点腐食量は最大となる。この硫酸露点腐食は、空気予熱器、電気集塵器、集電板、煙道、脱硫装置、煙突などの燃焼ガスが１５０℃以下に低下する部分で主に発生する。空気予熱器内の燃焼ガスは、１５０℃以上となっているが、燃焼用空気が通るパイプの表面は１５０℃以下になっており、このパイプに接触した燃焼ガスは１５０℃以下に温度低下し、硫酸が結露してこのパイプ部分で硫酸露点腐食が発生する。
【０００５】
かかる空気予熱器、電気集塵器、集電板、煙道、脱硫装置、煙突には、従来、低合金鋼、ステンレス鋼などのＦｅ基耐食合金が使用され、硫酸が結露することのないように保温されていたが、硫酸の凝縮を１００％防止することはできず、部位によっては硫酸露点腐食が発生するのを避けることはできなかった。そのため、脱硫装置などの一部において、Ｆｅ基合金に比べて格段に優れた耐硫酸腐食性を有するＮｉ基合金を用いることが多くなった。
【０００６】
これら個所に使用されるＮｉ基合金として、例えば、米国特許明細書第１６８２３７号記載の、重量％（以下、％は、重量％を示す）で、Ｃｒ：２１．５％、Ｍｏ：１３．２％、Ｆｅ：４．１％、Ｗ：３．０％を含有し、残部がＮｉおよび不可避不純物からなる組成を有するＮｉ基合金、特開昭５８−２５４５０号公報記載のＣｒ：３０．３％、Ｍｏ：５．１４％、Ｎｂ：０．５２％、Ｔａ：０．２１％、Ｆｅ：１５．１％、Ｗ：２．５３％を含有し、残部がＮｉおよび不可避不純物からなる組成を有するＮｉ基合金、ハステロイ（商品名）２４２と称するＣｒ：８．４％、Ｍｏ：２５．４％、Ｆｅ：１．６２％を含有し、残部がＮｉおよび不可避不純物からなる組成を有するＮｉ基合金、ハステロイ（商品名）Ｂ−２と称するＭｏ：２８．１％、Ｆｅ：１．９２％を含有し、残部がＮｉおよび不可避不純物からなる組成を有するＮｉ基合金、特開昭６２−４０３３７号公報記載のＣｒ：３０．４％、Ｍｏ：１９．６％を含有し、残部がＮｉおよび不可避不純物からなる組成を有するＮｉ基合金などがすでに知られている。
【０００７】
さらに、近年、Ｔａ：１．１〜３．５重量％を必須成分として含有する耐食性および加工性に一層優れたＮｉ基合金が提供されており、このＮｉ基合金は、重量％で、Ｃｒ：１６〜２７％、Ｍｏ：１６〜２５％（ただし、Ｃｒ＋Ｍｏ≦４４％）、Ｔａ：１．１〜３．５％、Ｆｅ：０．０１〜６％、Ｍｎ：０．０００１〜３％、Ｓｉ：０．０００１〜０．３％、Ｃ：０．００１〜０．１％、Ｍｇ：０．０００１〜０．３％を含有し、残部がＮｉおよび不可避不純物からなる組成を有するＮｉ基合金であることも知られている（特開平８−３６６６号公報参照）。
【０００８】
これら各種Ｎｉ基合金で空気予熱器、電気集塵器、集電板、煙道、脱硫装置、煙突を製造するには、一般に、これらＮｉ基合金板を溶接することにより製造する。このとき使用される被覆アーク溶接棒は、通常、前記Ｎｉ基合金板と同じ成分組成を有する心線に通常の金属炭酸塩、金属弗化物などを含む被覆剤を被覆してなる被覆アーク溶接棒が使用される。また、これらＮｉ基合金板を溶接するための一層好ましい被覆アーク溶接棒として、心線が６０％以上のＮｉ、１０〜２５％のＣｒ、かつ心線または被覆剤の一方または両方に心線重量比で０．０５〜３．０％のＴａを含有し、且つ被覆剤全重量に対して２５〜６０％の金属炭酸塩、１０〜３０％の金属弗化物が配合された被覆剤を被覆し、さらに被覆剤中の全水分量を０．２０％以下に制御したＮｉ−Ｃｒ基被覆アーク溶接棒が知られている（特公昭５９−６７５７号公報参照）。
【０００９】
【発明が解決しようとする課題】
しかし、Ｔａを含有するＮｉ基合金心線にＴａを含まない通常の被覆剤を塗布して得られたＮｉ基合金被覆アーク溶接棒を使用してＴａを含有するＮｉ基合金母材を溶接すると、得られた溶接金属に含まれるＴａは極端に減少し、溶接金属のＴａ含有量がＮｉ基合金母材に含まれるＴａ含有量よりも減少して溶接金属の耐硫酸露点腐食性が低下するとともに溶接金属の強度が低下するので好ましくない。
一方、被覆剤に金属Ｔａを添加したＮｉ基合金被覆アーク溶接棒を使用して同様にして溶接すると、得られる溶接金属のＴａ含有量は所望の範囲内に収まるが、被覆剤に含まれるＳｉが大量に溶接金属に固溶し、溶接金属のＳｉ含有量が０．３重量％を越えて含有するために粒界に析出物が生成し、脆化して溶接部の強度が低下するとともに耐硫酸露点腐食性が低下するので好ましくない。
【００１０】
このような現象は肉盛溶接を行って形成したライニングにも発生し、得られた溶着金属の耐硫酸腐食性が低下するので好ましくない。
【００１１】
【課題を解決する手段】
そこで、本発明者等は、硫酸露点腐食に対して十分な耐食性を示しさらに強度および靭性が低下することのない溶接金属を得ることのできるＮｉ基合金被覆アーク溶接棒、並びに硫酸露点腐食に対して十分な耐食性を示す溶着金属を得ることのできるＮｉ基合金被覆アーク肉盛溶接棒を開発すべく鋭意研究の結果、
（イ）心線として、重量％で、Ｃｒ：１６〜２７％、Ｍｏ：１６〜２５％（ただし、Ｃｒ＋Ｍｏ≦４４％）、Ｔａ：１．１〜３．５％、Ｆｅ：０．０１〜６％、Ｍｎ：０．０００１〜３％、Ｓｉ：０．０００１〜０．３％、Ｃ：０．００１〜０．１％、Ｍｇ：０．０００１〜０．３％を含有し、残部がＮｉおよび不可避不純物からなる組成を有するＮｉ基合金心線を作製し、このＮｉ基合金心線に、被覆剤全重量に対して酸化タンタル：５〜３５重量％を含む被覆剤を塗布してなるＮｉ基合金被覆アーク溶接棒を作製し、このＮｉ基合金被覆アーク溶接棒を使用して溶接して得られた溶接金属は、Ｔａ含有量が心線とほぼ同じ１．１〜３．５％の範囲内に調整することができかつＳｉ含有量も０．３％以下に抑えることができて十分な耐硫酸露点腐食性を示し、さらに強度および靭性が低下することがない、
（ロ）前記Ｎｉ基合金被覆アーク溶接棒を肉盛溶接に使用して得られた溶着金属は、Ｔａの含有量が心線とほぼ同じ１．１〜３．５％の範囲内に調整することができかつＳｉ含有量も０．３％以下に抑えることができて十分な耐硫酸露点腐食性を示す、という研究結果が得られたのである。
【００１２】
この発明は、かかる研究結果に基づいて成されたものであって、
（１）重量％で、Ｃｒ：１６〜２７％、Ｍｏ：１６〜２５％（ただし、Ｃｒ＋Ｍｏ≦４４％）、Ｔａ：１．１〜３．５％、Ｆｅ：０．０１〜６％、Ｍｎ：０．０００１〜３％、Ｓｉ：０．０００１〜０．３％、Ｃ：０．００１〜０．１％、Ｍｇ：０．０００１〜０．３％を含有し、残部がＮｉおよび不可避不純物からなる組成を有するＮｉ基合金心線に、被覆剤全重量に対して酸化タンタル：５〜３５重量％を含有し、さらに金属炭酸塩および金属弗化物を含有する組成の被覆剤を塗布してなるＮｉ基合金被覆アーク溶接棒、
（２）重量％で、Ｃｒ：１６〜２７％、Ｍｏ：１６〜２５％（ただし、Ｃｒ＋Ｍｏ≦４４％）、Ｔａ：１．１〜３．５％、Ｆｅ：０．０１〜６％、Ｍｎ：０．０００１〜３％、Ｓｉ：０．０００１〜０．３％、Ｃ：０．００１〜０．１％、Ｍｇ：０．０００１〜０．３％を含有し、残部がＮｉおよび不可避不純物からなる組成を有するＮｉ基合金心線に、被覆剤全重量に対して酸化タンタル：５〜３５重量％を含有し、さらに金属炭酸塩、金属弗化物および酸化タンタルを除く金属酸化物を含有する組成の被覆剤を塗布してなるＮｉ基合金被覆アーク溶接棒、
（３）重量％で、Ｃｒ：１６〜２７％、Ｍｏ：１６〜２５％（ただし、Ｃｒ＋Ｍｏ≦４４％）、Ｔａ：１．１〜３．５％、Ｆｅ：０．０１〜６％、Ｍｎ：０．０００１〜３％、Ｓｉ：０．０００１〜０．３％、Ｃ：０．００１〜０．１％、Ｍｇ：０．０００１〜０．３％を含有し、残部がＮｉおよび不可避不純物からなる組成を有するＮｉ基合金心線に、被覆剤全重量に対して金属炭酸塩：２５〜６０重量％、金属弗化物：１０〜３０重量％、酸化タンタル：５〜３５重量％を含有する組成の被覆剤を塗布してなるＮｉ基合金被覆アーク溶接棒、
（４）重量％で、Ｃｒ：１６〜２７％、Ｍｏ：１６〜２５％（ただし、Ｃｒ＋Ｍｏ≦４４％）、Ｔａ：１．１〜３．５％、Ｆｅ：０．０１〜６％、Ｍｎ：０．０００１〜３％、Ｓｉ：０．０００１〜０．３％、Ｃ：０．００１〜０．１％、Ｍｇ：０．０００１〜０．３％を含有し、残部がＮｉおよび不可避不純物からなる組成を有するＮｉ基合金心線に、被覆剤全重量に対して金属炭酸塩：２５〜６０重量％、金属弗化物：１０〜３０重量％、酸化タンタル：５〜３５重量％、酸化タンタルを除く金属酸化物：５〜５０重量％を含有する組成の被覆剤を塗布してなるＮｉ基合金被覆アーク溶接棒、に特徴を有するものである。
【００１３】
さらに、前記（１）〜（４）記載の組成を有する心線および被覆剤からなる溶接棒は、肉盛溶接棒としても使用することができる。
【００１４】
したがって、この発明は、
（５）前記（１）、（２）、（３）または（４）記載の組成を有する心線および被覆剤からなる肉盛溶接するためのＮｉ基合金被覆アーク肉盛溶接棒、に特徴を有するものである。
【００１５】
次に、この発明のＮｉ基合金被覆アーク溶接棒またはＮｉ基合金被覆アーク肉盛溶接棒におけるＮｉ基合金心線の成分組成の限定理由について詳述する。
【００１６】
Ｃｒ、Ｍｏ
ＣｒおよびＭｏ成分は、共に素地に固溶して耐食性向上を果たす成分であり、特にＣｒは酸化性酸に対する耐食性を向上させ、Ｍｏは非酸化性酸に対する耐食性を向上させる作用があることは知られているが、ＣｒおよびＭｏがＴａと同時に含有することにより各種の硫酸酸性環境、特に硫酸露点腐食環境において耐食性を向上させる作用がある。しかし、Ｃｒの含有量が１６％未満では合金表面に緻密な不働態被膜を形成することができないために十分な耐硫酸露点腐食性が得られず、一方、２７％を越えて含有すると、耐硫酸露点腐食性が劣化するので好ましくない。従って、Ｃｒの含有量を１６〜２７％に定めた。Ｃｒの一層好ましい含有量は１７〜２２％である。さらに、Ｍｏは１６％未満では十分な耐硫酸露点腐食性が得られず、一方、２５％を越えて含有すると、加工性が極端に低下し、伸線加工することが難しくなるので好ましくない。従って、Ｍｏ含有量は１６〜２５％に定めた。Ｍｏの一層好ましい含有量は１９〜２４％である。
【００１７】
Ｔａ
Ｔａ成分には、素地に固溶して不働態被膜を安定化させると同時に不働態化を促進させる効果があり、Ｃｒ：１６〜２７％、Ｍｏ：１６〜２５％を満足する量のＣｒおよびＭｏとともに含有させることにより、耐硫酸腐食性特に耐硫酸露点腐食性を向上させる成分であるが、その含有量が１．１％未満では所望の効果が得られず、一方、３．５％を越えて含有すると、合金のコストを大きく引き上げかつ加工性を低下させるので伸線加工することが難しくなり、したがってＮｉ基合金心線を作ることが難しくなるところから、その含有量を１．１〜３．５％に定めた。Ｔａの一層好ましい含有量は１．２〜３％である。
【００１８】
Ｆｅ
この発明のＮｉ基合金にはＣｒおよびＭｏが多量に含まれているため、塑性加工性が悪化するが、Ｆｅを０．０１％以上添加することにより加工性の低下を防ぐことができる。しかし、６％を越えて含有すると、加工性は向上するが、耐硫酸腐食性を著しく低下させることからその含有量を０．０１〜６％に定めた。Ｆｅの一層好ましい含有量は０．０１〜４％である。
【００１９】
Ｍｇ
Ｍｇ成分は、熱間加工性向上に多大に寄与するが、しかし、その含有量が０．０００１％未満では所望の効果が得られず、一方、０．３％を越えて含有するとＭｇが粒界に偏析して割れが発生し、熱間加工性が低下して伸線加工が難しくなるので好ましくない。したがって、Ｍｇの含有量を０．０００１〜０．３％に定めた。Ｍｇの一層好ましい含有量は０．００１〜０．０３％である。
【００２０】
Ｓｉ
Ｓｉは、脱酸剤として添加することにより、酸化物を低減する一方、粒界割れを抑制する効果があるため、熱間加工性を向上させるが、Ｓｉが０．３％を越えて含有すると、ＴＣＰ相の析出量の許容範囲を越えて熱間加工性が低下するとともに耐硫酸腐食性が低下するので好ましくない。したがってＳｉ含有量を０．３％以下に定めた。しかし、Ｓｉ含有量を０．０００１％にすると脱酸作用がなくなるのでＳｉ含有量の下限を０．０００１％とし、０．０００１〜０．３％とすることが好ましく、さらにＳｉの一層好ましい含有量は０．００１〜０．１％である。
【００２１】
Ｍｎ
Ｍｎ成分は、脱硫剤として添加されるが、３％を越えて含有すると、ＴＣＰ相の析出量の許容範囲を越え、耐食性が低下するので好ましくないことからその含有量を０．０００１〜３％に定めた。Ｍｎの一層好ましい含有量は０．００１〜１％である。
【００２２】
Ｃ
Ｃは、合金中に０．１％を越えて含有すると、粒界に存在する炭化物の量が増大するようになって、合金の延性および靭性が劣化するところからその含有量を０．００１〜０．１％に定めた。Ｃの一層好ましい含有量は０．００１〜０．０２％である。
【００２３】
不可避不純物
不可避不純物としてＳ、Ｓｎ、ＺｎおよびＰｂの含有は避けられない。しかし、Ｓ：０．０１％以下、Ｓｎ：０．０１％以下、Ｚｎ：０．０１％以下およびＰｂ：０．０１％以下であれば、合金特性はなんら損なわれるものではない。
【００２４】
この発明のＮｉ基合金被覆アーク溶接棒またはＮｉ基合金被覆アーク肉盛溶接棒に塗布する被覆剤は、被覆剤全重量に対して酸化タンタル：５〜３５重量％含有することが必須の構成用件である。この発明のＮｉ基合金被覆アーク溶接棒またはＮｉ基合金被覆アーク肉盛溶接棒の被覆剤に含まれる酸化タンタルが５重量％未満では、被覆剤に含まれるＳｉが溶接金属または溶着金属に大量に固溶し、溶接金属または溶着金属に含まれるＳｉ量を０．３％以下に抑制することができないために溶接金属または溶着金属の耐硫酸露点腐食性が低下するので好ましくなく、一方、この発明のＮｉ基合金被覆アーク溶接棒またはＮｉ基合金被覆アーク肉盛溶接棒の被覆剤に含まれる酸化タンタルが３５重量％を越えて含有すると、被覆剤のコストを引き上げかつスラグの流れが悪くなって良好なビード形状が得られなくなると共に溶接金属または溶着金属の靭性を低下させるので好ましくない。したがって、この発明のＮｉ基合金被覆アーク溶接棒またはＮｉ基合金被覆アーク肉盛溶接棒の被覆剤に含まれる酸化タンタルは５〜３５重量％に定めた。酸化タンタル含有量の一層好ましい範囲は１５〜３０重量％である。この発明のＮｉ基合金被覆アーク溶接棒またはＮｉ基合金被覆アーク肉盛溶接棒の被覆剤に含まれる酸化タンタルはＴａ2Ｏ5、ＴａＯ2、Ｔａ2Ｏ3などいかなる組成式を有していても良いが、これら酸化タンタルの内でもＴａ2Ｏ5が最も安定して入手しやすいので好ましい。
【００２５】
この発明のＮｉ基合金被覆アーク溶接棒またはＮｉ基合金被覆アーク肉盛溶接棒は、酸化タンタル粉末：５〜３５重量％、金属炭酸塩粉末：２５〜６０％、金属弗化物粉末：１０〜３０％、酸化タンタルを除く金属酸化物：５〜５０％をバインダーである水ガラス（珪酸カリ水溶液、珪酸ソーダ水溶液）に混合し、得られた混合物を前記Ｔａ：１．１〜３．５重量％、Ｓｉ：０．３重量％以下に規定したＮｉ基合金心線に被覆し、３８０〜４５０℃で乾燥し焼成することにより製造する。
この発明のＮｉ基合金被覆アーク溶接棒またはＮｉ基合金被覆アーク肉盛溶接棒のＮｉ基合金心線に被覆する被覆剤は、溶接棒全量に対して２０〜４０重量％となるように被覆することが好ましい。
【００２６】
次に、この発明のＮｉ基合金被覆アーク溶接棒またはＮｉ基合金被覆アーク肉盛溶接棒に被覆する被覆剤の酸化タンタル以外の成分組成を上述のごとく限定した理由を説明する。
金属炭酸塩
金属炭酸塩は、分解生成して発生する炭酸ガスによって溶接金属および溶着金属を保護し、スラグを高塩基性にする作用を有するので添加するが、その含有量が２５％未満では所望の効果が得られず、一方、６０％を越えて添加するとスラグの流れが悪くなり、良好なビードが得られなくなるので好ましくない。したがって、この発明のＮｉ基合金被覆アーク溶接棒またはＮｉ基合金被覆アーク肉盛溶接棒に被覆する被覆剤に含まれる金属炭酸塩は２５〜６０％に定めた。金属炭酸塩含有量の一層好ましい範囲は３０〜５５％である。前記金属炭酸塩は、炭酸カルシウム、炭酸バリウム、炭酸マグネシウム、炭酸リチウム、炭酸マンガンの内のいずれでも良く、あるいはこれらの複合添加物であっても良い。
【００２７】
金属弗化物
金属弗化物は、分解生成して発生するフッ素ガスによって溶接金属および溶着金属の水素量を下げ、溶接金属および溶着金属の耐割れ性を良好ならしめ、スラグの流動性を増す作用を有するが、その含有量が１０％未満では所望の効果が得られず、一方、３０％を越えて添加すると溶接棒の耐焼け性が劣化するので好ましくない。したがって、この発明のＮｉ基合金被覆アーク溶接棒またはＮｉ基合金被覆アーク肉盛溶接棒に被覆する被覆剤に含まれる金属弗化物は１０〜３０％に定めた。金属弗化物含有量の一層好ましい範囲は１４〜２６％である。前記金属弗化物は、螢石、氷晶石、弗化マグネシウム、弗化アルミニウム、弗化バリウム、弗化リチウム、弗化ナトリウムの内のいずれでも良く、あるいはこれらの複合添加物であっても良い。
【００２８】
酸化タンタルを除く金属酸化物
被覆剤には酸化タンタル以外の金属酸化物（例えば、酸化チタン、酸化アルミニウム、酸化珪素など）を添加してスラグの被包性を良くするが、その添加量が５％未満では所望の効果が得られず、一方、５０％を越えて添加するとスラグの流れが悪くなり、良好なビード形状が得られなくなるので好ましくない。
【００２９】
したがって、この発明のＮｉ基合金被覆アーク溶接棒またはＮｉ基合金被覆アーク肉盛溶接棒に被覆する被覆剤に含まれる酸化タンタルを除く金属酸化物は５〜５０％に定めた。酸化タンタルを除く金属酸化物含有量の一層好ましい範囲は１０〜４５％である。
【００３０】
【発明の実施の形態】
表１に示される成分組成を有し直径：３．２ｍｍのＮｉ基合金心線を用意し、さらに、Ｔａ2Ｏ5粉末、ＣａＣＯ3粉末、ＣａＦ2粉末、Ｔｉ2Ｏ3粉末、Ａｌ2Ｏ3粉末を用意し、これら粉末を水ガラスと混和することにより混合物を作製した。これら混合物を前記Ｎｉ基合金心線に塗布したのち４００℃で焼成することにより表１に示される成分を含む被覆剤を表１に示される成分組成のＮｉ基合金心線に被覆した本発明Ｎｉ基合金被覆アーク溶接棒（以下、本発明溶接棒という）１〜８、比較Ｎｉ基合金被覆アーク溶接棒（以下、比較溶接棒という）１〜２および従来Ｎｉ基合金被覆アーク溶接棒（以下、従来溶接棒という）１を作製した。
【００３１】
【表１】
実施例１
本発明溶接棒１〜８、比較溶接棒１〜２および従来溶接棒１を用い、溶接電流：１４０Ａ（交流）、アーク電圧：２２〜２６Ｖで肉盛溶接することにより溶着金属を形成し、表２に示される成分組成の溶着金属を有する溶着金属試験片を作製した。
【００３３】
【表２】
一方、６０％Ｈ2ＳＯ4 および８０％Ｈ2ＳＯ4 を用意し、
６０％Ｈ2ＳＯ4 ３ｃｃにつき活性炭微粉末１ｇの割合で懸濁させた液（以下、６０％Ｈ2ＳＯ4 ＋活性炭と記す）、
８０％Ｈ2ＳＯ4 ３ｃｃにつき活性炭微粉末１ｇの割合で懸濁させた液（以下、８０％Ｈ2ＳＯ4 ＋活性炭と記す）、
６０％Ｈ2ＳＯ4 につき１００ｐｐｍのＨＣｌを添加した液（以下、６０％Ｈ2ＳＯ4 ＋ＨＣｌと記す）、
６０％Ｈ2ＳＯ4 につき１０ｐｐｍのＨＮＯ3 を添加した液（以下、６０％Ｈ2ＳＯ4 ＋ＨＮＯ3 と記す）、
６０％Ｈ2ＳＯ4 につき４００ｐｐｍのＦｅ3+を添加した液（以下、６０％Ｈ2ＳＯ4 ＋Ｆｅ3+と記す）、
をそれぞれ用意した。
【００３５】
これら硫酸溶液を温度：１２０℃に加熱し、この加熱した硫酸溶液に前記溶着金属試験片をそれぞれ２４時間浸漬し、取り出して重さを測定し、減少した重量を表面積と時間で割り、１年間の腐食速度（ｍｍ／ｙｅａｒ）を算出し、その値を表３に示した。
【００３６】
【表３】
表２および表３に示される結果から、本発明溶接棒１〜８を用いて形成した溶着金属は、比較溶接棒１を用いて形成したＴａ含有量が所定の量より少ない溶着金属および従来溶接棒１を用いて形成したＳｉ含有量が所定の量より多い溶着金属に比べていずれも優れた耐食性を示すことが分かる。さらにＴａ2Ｏ5を３５重量％を越えて含む被覆剤を塗布した比較溶接棒２は溶接時のスラグの流動性が低下し、平滑なビードを得ることができなくなるので好ましくないことが分かる。
【００３８】
したがって、この発明の被覆アーク溶接棒を用いて、例えば、空気予熱器、電気集塵器、集電板、煙道、脱硫装置、煙突などの裏面にライニングを施して耐硫酸露点腐食性を向上させることができることが分かる。
【００３９】
実施例２
表１に示される本発明溶接棒１〜８、比較溶接棒１〜２および従来溶接棒１を用い、溶接電流：１４０Ａ（交流）、アーク電圧：２２〜２６Ｖの条件で、Ｃｒ：１９％、Ｍｏ：１９％、Ｔａ：１．８％、Ｆｅ：０．０５％、Ｍｎ：０．０１％、Ｓｉ：０．０３％、Ｃ：０．００２％、Ｍｇ：０．００１％を含有し、残部：Ｎｉおよび不可避不純物からなるＮｉ基合金板母材を溶接し、得られた溶接継ぎ手から溶接線に直行する方向に平行部に溶接金属、溶接熱影響部、母材を含むＪＩＳ５号引張り試験片を採取し、室温で引張り試験を行い、引張り強さおよびその破断位置を測定し、それらの結果を表４に示した。
【００４０】
【表４】
表４に示される結果から、引張り試験の際の破断位置は、本発明溶接棒１〜８を用いた場合はいずれも母材であるに対し、比較溶接棒１〜２および従来溶接棒１を用いた場合は溶接金属部であり、本発明溶接棒１〜８を用いて形成した溶接部の引張り強さは、比較溶接棒１〜２および従来溶接棒１を用いて形成した溶接部に比べていずれも優れていることが分かる。
【００４２】
【発明の効果】
上述のように、この発明のＮｉ基合金被覆アーク溶接棒を用いて作製した装置は、硫酸腐食を主とする湿潤な腐食環境下においても溶接部の強度および耐食性に優れ、長期間使用することができ、産業上優れた効果をもたらすものである。[0001]
[Industrial application fields]
The present invention relates to a Ni-base alloy-coated arc welding rod for welding a Ni-base alloy excellent in corrosion resistance, particularly sulfuric acid corrosion resistance, and also overlays a lining excellent in corrosion resistance, particularly sulfuric acid corrosion resistance. The present invention relates to a Ni-based alloy-coated arc overlay welding rod for forming by welding.
[0002]
[Prior art]
For example, in a thermal power plant, B, C heavy oil, coal, or the like is burned in a boiler, pure water is heated to produce high-temperature steam, and the steam turbine is rotated using this high-temperature steam to generate power. The combustion gas generated in this boiler is first denitrated by a denitration device, then sent to an air preheater to heat the combustion air, further desulfurized by the desulfurization device, and then released from the chimney to the atmosphere. . The combustion gas from which NO x has been removed by the denitration device is sent to an air preheater, where it is cooled to 150 to 250 ° C. by preheating the combustion air, and further passed through the desulfurization device to less than 150 ° C. (usually Is cooled to about 80 ° C. and then released from the chimney.
[0003]
The temperature of the combustion gas denitrated by the denitration device falls to 250 ° C. or less, but its components contain a large amount of CO x and SO x in addition to air, other HCl, a small amount of NO x that has not been denitrated, It is said to contain Fe 3+ ions generated from the device, and further to include solid suspended matters such as unburned carbon soot and dust. When the combustion gas that has passed through the denitration device is cooled to about 150 ° C., the water vapor and SO 3 react to form H 2 SO 4 and form dew, producing about 80% concentrated sulfuric acid. This condensed sulfuric acid contains corrosive gases such as HCl, NO x , O 2 , and CO x and oxidizing ion Fe 3+, and also contains fine carbon and dust that is the main body of soot. .
[0004]
Condensed sulfuric acid containing such various corrosive factors is particularly corrosive. Corrosion caused by the condensed sulfuric acid is referred to as “sulfuric acid dew point corrosion”. Since the amount of water vapor and SO 3 reacting to form H 2 SO 4 and condensing becomes maximum in the temperature range of 110 to 130 ° C., the sulfuric acid dew point corrosion amount of the metal material becomes maximum in this temperature range. This sulfuric acid dew point corrosion is mainly generated in a portion where the combustion gas is lowered to 150 ° C. or lower, such as an air preheater, an electrostatic precipitator, a current collector plate, a flue, a desulfurizer, and a chimney. The combustion gas in the air preheater is 150 ° C. or higher, but the surface of the pipe through which combustion air passes is 150 ° C. or lower, and the temperature of the combustion gas in contact with this pipe drops to 150 ° C. or lower. Sulfuric acid is condensed and sulfuric acid dew point corrosion occurs in this pipe part.
[0005]
Such air preheaters, electrostatic precipitators, current collector plates, flues, desulfurizers, and chimneys have conventionally used Fe-based corrosion-resistant alloys such as low alloy steel and stainless steel to prevent condensation of sulfuric acid. However, the condensation of sulfuric acid could not be prevented 100%, and it was impossible to avoid the occurrence of sulfuric acid dew point corrosion depending on the part. For this reason, in some desulfurization apparatuses and the like, a Ni-based alloy having a sulfuric acid corrosion resistance that is remarkably superior to that of an Fe-based alloy is often used.
[0006]
As Ni-based alloys used in these places, for example, as described in U.S. Pat. No. 168237, wt% (hereinafter,% indicates wt%), Cr: 21.5%, Mo: 13.2 %, Fe: 4.1%, W: 3.0%, a Ni-based alloy having a composition consisting of Ni and inevitable impurities, Cr: 30.3% described in JP-A-58-25450 , Mo: 5.14%, Nb: 0.52%, Ta: 0.21%, Fe: 15.1%, W: 2.53%, with the balance being Ni and inevitable impurities Ni-based alloy, called Hastelloy (trade name) 242, containing Cr: 8.4%, Mo: 25.4%, Fe: 1.62%, with the balance being composed of Ni and inevitable impurities Mo, referred to as Hastelloy (trade name) B-2: 28. %, Fe: 1.92%, Ni-based alloy having a composition consisting of Ni and inevitable impurities, Cr: 30.4%, Mo: 19.6% described in JP-A No. 62-40337 Ni-based alloys having a composition containing Ni and the balance of Ni and inevitable impurities are already known.
[0007]
Furthermore, in recent years, a Ni-based alloy having an excellent corrosion resistance and workability containing Ta: 1.1 to 3.5% by weight as an essential component has been provided. This Ni-based alloy is Cr: 16 to 27%, Mo: 16 to 25% (provided that Cr + Mo ≦ 44%), Ta: 1.1 to 3.5%, Fe: 0.01 to 6%, Mn: 0.0001 to 3%, Si : Ni-based alloy containing 0.0001-0.3%, C: 0.001-0.1%, Mg: 0.0001-0.3%, the balance being composed of Ni and inevitable impurities It is also known (see JP-A-8-3666).
[0008]
In order to manufacture an air preheater, an electrostatic precipitator, a current collector plate, a flue, a desulfurization device, and a chimney with these various Ni-based alloys, these Ni-based alloy plates are generally manufactured by welding. The coated arc welding rod used at this time is usually a coated arc welding rod formed by coating a core wire having the same component composition as the Ni-based alloy plate with a coating agent containing a normal metal carbonate, metal fluoride, etc. Is used. Further, as a more preferable coated arc welding rod for welding these Ni-based alloy plates, the core wire has a core wire weight of 60% or more of Ni, 10 to 25% Cr, and one or both of the core wire and the coating material. A coating agent containing 0.05 to 3.0% Ta by weight and containing 25 to 60% metal carbonate and 10 to 30% metal fluoride based on the total weight of the coating was coated. Furthermore, a Ni—Cr-based coated arc welding rod in which the total water content in the coating is controlled to 0.20% or less is known (see Japanese Patent Publication No. 59-6757).
[0009]
[Problems to be solved by the invention]
However, when a Ni-based alloy base material containing Ta is welded using a Ni-based alloy-coated arc welding rod obtained by applying an ordinary coating agent not containing Ta to a Ni-based alloy core wire containing Ta. In addition, Ta contained in the obtained weld metal is extremely reduced, and the Ta content of the weld metal is smaller than the Ta content contained in the Ni-based alloy base material, thereby reducing the sulfuric acid dew point corrosion resistance of the weld metal. At the same time, the strength of the weld metal decreases, which is not preferable.
On the other hand, when welding is performed in the same manner using a Ni-based alloy-coated arc welding rod in which metal Ta is added to the coating, the Ta content of the obtained weld metal falls within the desired range, but Si contained in the coating Is dissolved in a large amount in the weld metal, and since the Si content of the weld metal exceeds 0.3% by weight, precipitates are formed at the grain boundaries, embrittlement occurs and the weld strength decreases and Since sulfuric acid dew point corrosion property falls, it is not preferable.
[0010]
Such a phenomenon also occurs in a lining formed by overlay welding, and is not preferable because sulfuric acid corrosion resistance of the obtained deposited metal is lowered.
[0011]
[Means for solving the problems]
Accordingly, the present inventors have provided Ni-base alloy-coated arc welding rods that can provide a weld metal that exhibits sufficient corrosion resistance against sulfuric acid dew point corrosion and that does not deteriorate strength and toughness, and sulfuric acid dew point corrosion. As a result of diligent research to develop a Ni-based alloy-coated arc overlay welding rod that can obtain a weld metal exhibiting sufficient corrosion resistance,
(B) As a core wire, by weight%, Cr: 16 to 27%, Mo: 16 to 25% (provided that Cr + Mo ≦ 44%), Ta: 1.1 to 3.5%, Fe: 0.01 to 6%, Mn: 0.0001-3%, Si: 0.0001-0.3%, C: 0.001-0.1%, Mg: 0.0001-0.3%, the balance being A Ni-based alloy core wire having a composition composed of Ni and inevitable impurities is prepared, and a coating agent containing 5-35% by weight of tantalum oxide with respect to the total weight of the coating agent is applied to the Ni-based alloy core wire. A weld metal obtained by producing a Ni-base alloy-coated arc welding rod and welding using this Ni-base alloy-coated arc welding rod has a Ta content of 1.1 to 3.5% which is substantially the same as that of the core wire. Sulfuric acid resistance that can be adjusted within the range and the Si content can be suppressed to 0.3% or less. Shows the pitting resistance, is not reduced further strength and toughness,
(B) The deposited metal obtained by using the Ni-based alloy-coated arc welding rod for overlay welding is adjusted so that the Ta content is in the range of 1.1 to 3.5%, which is substantially the same as the core wire. The result of the study was that it was possible to suppress the Si content to 0.3% or less and to exhibit sufficient sulfuric acid dew point corrosion resistance.
[0012]
The present invention has been made based on such research results,
(1) By weight, Cr: 16-27%, Mo: 16-25% (however, Cr + Mo ≦ 44%), Ta: 1.1-3.5%, Fe: 0.01-6%, Mn : 0.0001-3%, Si: 0.0001-0.3%, C: 0.001-0.1%, Mg: 0.0001-0.3%, the balance being Ni and inevitable impurities A Ni-based alloy core wire having a composition comprising: a coating agent containing 5 to 35% by weight of tantalum oxide based on the total weight of the coating agent, and further containing a metal carbonate and a metal fluoride. Ni-based alloy-coated arc welding rod,
(2) By weight, Cr: 16-27%, Mo: 16-25% (provided that Cr + Mo ≦ 44%), Ta: 1.1-3.5%, Fe: 0.01-6%, Mn : 0.0001-3%, Si: 0.0001-0.3%, C: 0.001-0.1%, Mg: 0.0001-0.3%, the balance being Ni and inevitable impurities The Ni-based alloy core wire having a composition comprising: tantalum oxide: 5 to 35% by weight based on the total weight of the coating agent; and further containing metal oxides excluding metal carbonate, metal fluoride and tantalum oxide. A Ni-based alloy-coated arc welding rod formed by applying a coating material having a composition;
(3)% by weight: Cr: 16-27%, Mo: 16-25% (provided Cr + Mo ≦ 44%), Ta: 1.1-3.5%, Fe: 0.01-6%, Mn : 0.0001-3%, Si: 0.0001-0.3%, C: 0.001-0.1%, Mg: 0.0001-0.3%, the balance being Ni and inevitable impurities A Ni-based alloy core wire having a composition consisting of: metal carbonate: 25-60% by weight, metal fluoride: 10-30% by weight, tantalum oxide: 5-35% by weight with respect to the total weight of the coating agent A Ni-based alloy-coated arc welding rod formed by applying a coating material having a composition;
(4)% by weight: Cr: 16-27%, Mo: 16-25% (provided Cr + Mo ≦ 44%), Ta: 1.1-3.5%, Fe: 0.01-6%, Mn : 0.0001-3%, Si: 0.0001-0.3%, C: 0.001-0.1%, Mg: 0.0001-0.3%, the balance being Ni and inevitable impurities Ni-based alloy core wire having a composition consisting of: metal carbonate: 25-60% by weight, metal fluoride: 10-30% by weight, tantalum oxide: 5-35% by weight, tantalum oxide, based on the total weight of the coating agent The metal oxide except for: a Ni-base alloy-coated arc welding rod formed by applying a coating agent having a composition containing 5 to 50% by weight.
[0013]
Furthermore, the welding rod which consists of a core wire and a coating material which have a composition of said (1)-(4) description can be used also as a build-up welding rod.
[0014]
Therefore, the present invention
(5) A feature of the Ni-based alloy-covered arc overlay welding rod for overlay welding comprising a core wire and a coating material having the composition described in (1), (2), (3) or (4) above. It is what you have.
[0015]
Next, the reason for limiting the component composition of the Ni-based alloy core wire in the Ni-based alloy-coated arc welding rod or the Ni-based alloy-coated arc welding rod according to the present invention will be described in detail.
[0016]
Cr, Mo
Both the Cr and Mo components are components that dissolve in the substrate to improve the corrosion resistance. In particular, it is known that Cr has an effect of improving the corrosion resistance against oxidizing acids, and Mo has an action of improving the corrosion resistance against non-oxidizing acids. However, when Cr and Mo are contained simultaneously with Ta, there is an effect of improving the corrosion resistance in various sulfuric acid environments, particularly in a sulfuric acid dew point corrosion environment. However, if the Cr content is less than 16%, a dense passive film cannot be formed on the alloy surface, so that sufficient sulfuric acid dew point corrosion resistance cannot be obtained. Since sulfuric acid dew point corrosion property deteriorates, it is not preferable. Therefore, the content of Cr is set to 16 to 27%. A more preferable content of Cr is 17 to 22%. Further, if Mo is less than 16%, sufficient sulfuric acid dew point corrosion resistance cannot be obtained. On the other hand, if it exceeds 25%, the workability is extremely lowered, and it becomes difficult to perform wire drawing, which is not preferable. Therefore, the Mo content is set to 16 to 25%. A more preferable content of Mo is 19 to 24%.
[0017]
Ta
The Ta component has the effect of solid-dissolving in the substrate to stabilize the passive film and at the same time promote the passivation, Cr in an amount satisfying Cr: 16-27%, Mo: 16-25% Although it is a component that improves sulfuric acid corrosion resistance, particularly sulfuric acid dew point corrosion resistance, when it is contained together with Mo, the desired effect cannot be obtained if its content is less than 1.1%, while 3.5% If it is contained in excess, the cost of the alloy is greatly increased and the workability is lowered, so that it becomes difficult to perform wire drawing, and therefore it becomes difficult to make a Ni-based alloy core wire. Set to 3.5%. A more preferable content of Ta is 1.2 to 3%.
[0018]
Fe
Since the Ni-based alloy of this invention contains a large amount of Cr and Mo, the plastic workability deteriorates, but the addition of 0.01% or more of Fe can prevent the workability from decreasing. However, if the content exceeds 6%, the workability is improved, but the sulfuric acid corrosion resistance is remarkably lowered, so the content was set to 0.01 to 6%. A more preferable content of Fe is 0.01 to 4%.
[0019]
Mg
The Mg component greatly contributes to the improvement of hot workability. However, if the content is less than 0.0001%, the desired effect cannot be obtained. It is not preferable because it segregates at the boundary and cracks occur, and hot workability deteriorates and wire drawing becomes difficult. Therefore, the content of Mg is set to 0.0001 to 0.3%. A more preferable content of Mg is 0.001 to 0.03%.
[0020]
Si
When Si is added as a deoxidizer, it reduces oxides, while it has the effect of suppressing intergranular cracking, so it improves hot workability, but if Si contains more than 0.3% Further, it is not preferable because the hot workability is lowered and the sulfuric acid corrosion resistance is lowered while exceeding the allowable range of the precipitation amount of the TCP phase. Therefore, the Si content is set to 0.3% or less. However, if the Si content is 0.0001%, the deoxidizing action is eliminated, so the lower limit of the Si content is preferably 0.0001%, preferably 0.0001 to 0.3%, and more preferably Si is contained. The amount is 0.001 to 0.1%.
[0021]
Mn
The Mn component is added as a desulfurizing agent. However, if it exceeds 3%, it exceeds the allowable range of the precipitation amount of the TCP phase, and the corrosion resistance is lowered. Determined. A more preferable content of Mn is 0.001 to 1%.
[0022]
C
If the C content exceeds 0.1% in the alloy, the amount of carbides present at the grain boundaries will increase, and the ductility and toughness of the alloy will deteriorate. Set to 0.1%. The more preferable content of C is 0.001 to 0.02%.
[0023]
Inevitable impurities The inclusion of S, Sn, Zn and Pb as inevitable impurities is inevitable. However, if S: 0.01% or less, Sn: 0.01% or less, Zn: 0.01% or less and Pb: 0.01% or less, the alloy characteristics are not impaired at all.
[0024]
The coating material applied to the Ni-base alloy-coated arc welding rod or Ni-base alloy-coated arc welding rod according to the present invention is required to contain 5 to 35% by weight of tantalum oxide with respect to the total weight of the coating material. It is matter. When the tantalum oxide contained in the coating material of the Ni-base alloy-coated arc welding rod or Ni-base alloy-coated arc welding rod of this invention is less than 5% by weight, a large amount of Si contained in the coating material is present in the weld metal or weld metal. This is not preferable because the amount of Si contained in the weld metal or the weld metal cannot be suppressed to 0.3% or less because the resistance to sulfuric acid dew point corrosion of the weld metal or the weld metal is lowered. If the tantalum oxide contained in the coating material of the Ni-base alloy-coated arc welding rod or Ni-base alloy-coated arc welding rod exceeds 35% by weight, the cost of the coating material is increased and the flow of slag is deteriorated. This is not preferable because a good bead shape cannot be obtained and the toughness of the weld metal or weld metal is lowered. Therefore, the tantalum oxide contained in the coating material of the Ni-base alloy-coated arc welding rod or Ni-base alloy-coated arc welding rod of the present invention is set to 5 to 35% by weight. A more preferable range of the tantalum oxide content is 15 to 30% by weight. The tantalum oxide contained in the coating material of the Ni-base alloy-coated arc welding rod or Ni-base alloy-coated arc welding rod of this invention has any composition formula such as Ta 2 O 5 , TaO 2 , Ta 2 O 3. Of these tantalum oxides, Ta 2 O 5 is preferred because it is most stable and easily available.
[0025]
The Ni-base alloy-coated arc welding rod or the Ni-base alloy-coated arc welding rod according to the present invention comprises tantalum oxide powder: 5 to 35% by weight, metal carbonate powder: 25 to 60%, metal fluoride powder: 10 to 30 %, Metal oxide excluding tantalum oxide: 5 to 50% was mixed with water glass (potassium silicate aqueous solution, sodium silicate aqueous solution) as a binder, and the resulting mixture was Ta: 1.1 to 3.5% by weight , Si: It is manufactured by coating a Ni-based alloy core wire specified to 0.3 wt% or less, drying at 380 to 450 ° C. and firing.
The coating agent for coating the Ni-based alloy core wire of the Ni-based alloy-coated arc welding rod or the Ni-based alloy-coated arc welding rod of this invention is coated so as to be 20 to 40% by weight based on the total amount of the welding rod. It is preferable.
[0026]
Next, the reason why the component composition other than tantalum oxide of the coating agent coated on the Ni-base alloy-coated arc welding rod or Ni-base alloy-coated arc welding rod of the present invention is limited as described above will be described.
Metal carbonate Metal carbonate is added because it has the effect of protecting weld metal and weld metal by carbon dioxide generated by decomposition and making slag highly basic, but it is desirable if its content is less than 25%. On the other hand, if it is added over 60%, the flow of slag is deteriorated, and a good bead cannot be obtained. Therefore, the metal carbonate contained in the coating agent coated on the Ni-base alloy-coated arc welding rod or Ni-base alloy-coated arc welding rod of the present invention is set to 25 to 60%. A more preferable range of the metal carbonate content is 30 to 55%. The metal carbonate may be any of calcium carbonate, barium carbonate, magnesium carbonate, lithium carbonate, manganese carbonate, or a composite additive thereof.
[0027]
Metal fluoride Metal fluoride reduces the amount of hydrogen in the weld metal and weld metal by the fluorine gas generated by decomposition, improves the crack resistance of the weld metal and weld metal, and increases the fluidity of the slag. However, if the content is less than 10%, the desired effect cannot be obtained. On the other hand, if the content exceeds 30%, the burn resistance of the welding rod deteriorates, which is not preferable. Therefore, the metal fluoride contained in the coating material coated on the Ni-base alloy-coated arc welding rod or Ni-base alloy-coated arc welding rod of the present invention is set to 10 to 30%. A more preferable range of the metal fluoride content is 14 to 26%. The metal fluoride may be any of meteorite, cryolite, magnesium fluoride, aluminum fluoride, barium fluoride, lithium fluoride, and sodium fluoride, or a composite additive thereof. .
[0028]
Metal oxide excluding tantalum oxide A metal oxide other than tantalum oxide (for example, titanium oxide, aluminum oxide, silicon oxide, etc.) is added to the coating agent to improve the encapsulation of slag. If it is less than 50%, the desired effect cannot be obtained. On the other hand, if it is added in excess of 50%, the flow of slag deteriorates, and a good bead shape cannot be obtained.
[0029]
Therefore, the metal oxide excluding tantalum oxide contained in the coating material coated on the Ni-base alloy-coated arc welding rod or Ni-base alloy-coated arc welding rod of the present invention is set to 5 to 50%. A more preferable range of the metal oxide content excluding tantalum oxide is 10 to 45%.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
A Ni-based alloy core wire having the composition shown in Table 1 and a diameter of 3.2 mm is prepared, and Ta 2 O 5 powder, CaCO 3 powder, CaF 2 powder, Ti 2 O 3 powder, Al 2 O are prepared. Three powders were prepared, and these powders were mixed with water glass to prepare a mixture. The present invention Ni in which a coating agent containing the components shown in Table 1 was coated on a Ni-based alloy core wire having the component composition shown in Table 1 by applying the mixture to the Ni-base alloy core wire and firing at 400 ° C. Base alloy-coated arc welding rods (hereinafter referred to as the present invention welding rods) 1 to 8, Comparative Ni-based alloy coated arc welding rods (hereinafter referred to as comparative welding rods) 1 and 2 and conventional Ni-based alloy coated arc welding rods (hereinafter referred to as “welding rods”) A conventional welding rod 1) was produced.
[0031]
[Table 1]
Example 1
Using the welding rods 1 to 8 of the present invention, the comparative welding rods 1 and 2 and the conventional welding rod 1, weld metal is formed by overlay welding at a welding current of 140 A (alternating current) and an arc voltage of 22 to 26 V, The weld metal test piece which has the weld metal of the component composition shown by 2 was produced.
[0033]
[Table 2]
On the other hand, 60% H 2 SO 4 and 80% H 2 SO 4 are prepared,
A liquid suspended at a rate of 1 g of activated carbon fine powder per 3 cc of 60% H 2 SO 4 (hereinafter referred to as 60% H 2 SO 4 + activated carbon),
A liquid suspended at a rate of 1 g of activated carbon fine powder per 3 cc of 80% H 2 SO 4 (hereinafter referred to as 80% H 2 SO 4 + activated carbon),
A solution in which 100 ppm of HCl is added per 60% H 2 SO 4 (hereinafter referred to as 60% H 2 SO 4 + HCl),
A solution in which 10 ppm of HNO 3 is added per 60% H 2 SO 4 (hereinafter referred to as 60% H 2 SO 4 + HNO 3 ),
A solution in which 400 ppm of Fe 3+ is added per 60% H 2 SO 4 (hereinafter referred to as 60% H 2 SO 4 + Fe 3+ ),
Prepared.
[0035]
These sulfuric acid solutions were heated to a temperature of 120 ° C., and the weld metal specimens were each immersed in the heated sulfuric acid solution for 24 hours, removed and weighed, and the reduced weight was divided by the surface area and time for one year. The corrosion rate (mm / year) was calculated and the value is shown in Table 3.
[0036]
[Table 3]
From the results shown in Table 2 and Table 3, the weld metal formed using the welding rods 1 to 8 of the present invention is a weld metal formed using the comparative welding rod 1 and a conventional weld with a Ta content less than a predetermined amount. It can be seen that all of them show excellent corrosion resistance as compared with the weld metal having a Si content formed using the rod 1 larger than a predetermined amount. Furthermore, it can be seen that the comparative welding rod 2 coated with a coating containing more than 35% by weight of Ta 2 O 5 is not preferable because the fluidity of the slag during welding decreases and a smooth bead cannot be obtained.
[0038]
Therefore, by using the coated arc welding rod of the present invention, for example, the back surface of an air preheater, an electrostatic precipitator, a current collector plate, a flue, a desulfurizer, a chimney, etc. is lined to improve sulfuric acid dew point corrosion resistance. You can see that
[0039]
Example 2
Using welding rods 1 to 8 of the present invention, comparative welding rods 1 and 2 and conventional welding rod 1 shown in Table 1, welding current: 140 A (alternating current), arc voltage: 22-26 V, Cr: 19%, Mo: 19%, Ta: 1.8%, Fe: 0.05%, Mn: 0.01%, Si: 0.03%, C: 0.002%, Mg: 0.001%, Remainder: JIS No. 5 tensile test including weld metal, weld heat affected zone, and base metal in parallel to the direction perpendicular to the weld line from the weld joint obtained by welding Ni and inevitable impurities Ni base alloy base metal Pieces were collected and subjected to a tensile test at room temperature, the tensile strength and the breaking position thereof were measured, and the results are shown in Table 4.
[0040]
[Table 4]
From the results shown in Table 4, the break position during the tensile test is the base material when the welding rods 1 to 8 of the present invention are used, whereas the comparative welding rods 1 and 2 and the conventional welding rod 1 are used. When used, it is a weld metal part, and the tensile strength of the weld part formed using the welding rods 1 to 8 of the present invention is higher than that of the weld part formed using the comparative welding rods 1 and 2 and the conventional welding rod 1. It turns out that both are excellent.
[0042]
【The invention's effect】
As described above, the apparatus manufactured using the Ni-based alloy-coated arc welding rod of the present invention is excellent in the strength and corrosion resistance of the welded part even in a wet corrosive environment mainly composed of sulfuric acid corrosion, and should be used for a long time. It is possible to produce an excellent industrial effect.
Claims (5)
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Cited By (2)
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| CN110170769A (en) * | 2019-05-31 | 2019-08-27 | 湖北船王特种焊材有限公司 | It is a kind of containing rare earth, the stainless steel electrode of carbon steel core and preparation method |
| US10675720B2 (en) | 2011-02-01 | 2020-06-09 | Mitsubishi Heavy Industries, Ltd. | High Cr Ni-based alloy welding wire, shielded metal arc welding rod, and weld metal formed by shielded metal arc welding |
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| US8568901B2 (en) | 2006-11-21 | 2013-10-29 | Huntington Alloys Corporation | Filler metal composition and method for overlaying low NOx power boiler tubes |
| CN102441742B (en) * | 2011-10-13 | 2014-02-12 | 天津市金桥焊材集团有限公司 | Welding rod with high rust resistance |
| JP6296550B2 (en) * | 2014-08-25 | 2018-03-20 | 株式会社神戸製鋼所 | Ni-base alloy-coated arc welding rod |
| CN114101965B (en) * | 2021-11-25 | 2023-06-23 | 河钢股份有限公司 | Nickel-chromium-molybdenum corrosion-resistant alloy welding rod and preparation method thereof |
| CN115229383B (en) * | 2022-09-23 | 2022-12-16 | 四川西冶新材料股份有限公司 | Acid stainless steel welding rod free of repeated baking and preparation method thereof |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| US10675720B2 (en) | 2011-02-01 | 2020-06-09 | Mitsubishi Heavy Industries, Ltd. | High Cr Ni-based alloy welding wire, shielded metal arc welding rod, and weld metal formed by shielded metal arc welding |
| CN110170769A (en) * | 2019-05-31 | 2019-08-27 | 湖北船王特种焊材有限公司 | It is a kind of containing rare earth, the stainless steel electrode of carbon steel core and preparation method |
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