JP4291573B2 - Steel and air preheater with excellent resistance to sulfuric acid dew point corrosion - Google Patents
Steel and air preheater with excellent resistance to sulfuric acid dew point corrosion Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
Description
【０００１】
【発明の属する技術分野】
本発明は、重油、石炭、ごみ等を燃焼させた排ガスに曝される煙道、煙突、ボイラー空気予熱器などの設備に使用される耐硫酸露点腐食性に優れた鋼材に関する。
【０００２】
【従来の技術】
イオウ分を含有する燃料を燃焼させると、排ガス中にSOX が生じ、これが排ガス中の水分と化合して硫酸が生じる。排ガスの温度が低下して、およそ160 ℃程度の硫酸の露点に到達すると、硫酸ガスが凝結して、鋼材表面に硫酸濃度80〜90％程度の高濃度硫酸が付着して腐食が生じる。そして、さらに、80℃近傍まで温度が低下すると、水の凝結が加わって硫酸濃度40〜50％程度の比較的低濃度の硫酸が形成されて、腐食が加速される。すなわち、凝結硫酸による鋼材が腐食される条件としては、図１に示すように、比較的高温高濃度の条件と低温低濃度の条件の２つがある。
【０００３】
このような硫酸露点腐食問題に対し、従来より硫酸環境において耐食性を発揮する鋼材が開発されてきている。例えば、特公昭43-14585号公報に開示されたように、耐硫酸腐食性に有効なSb，Cuを複合添加した低合金鋼が実用に供されてきている。
【０００４】
しかしながら、従来の鋼は、前述の２つの腐食条件(160℃近傍、80〜90％硫酸の条件と、80℃近傍、40〜50％硫酸の条件）における耐食性を両立させるものではなかった。このため、起動、停止を繰り返し高温から低温までのサイクルに頻繁に曝されるプラントでは、必ずしも所期の耐食性を発揮するとは限らないという問題があった。
【０００５】
【発明が解決しようとする課題】
以上の状況に鑑み、本発明は、高温から低温に至る全温度域の硫酸露点腐食環境において、優れた耐食性を確保できる鋼材及びこれを用いた空気予熱器を提供するものである。
【０００６】
【課題を解決するための手段】
前記の課題に対し、本発明者らは、種々の鋼成分の供試材を作製し、低温条件として、（ａ）40％硫酸、60℃、（ｂ）50％硫酸、80℃の２条件、および、高温条件として、（ｃ）80％硫酸、140 ℃、（ｄ）90％硫酸、160 ℃の２条件、計４条件における腐食試験を行い、４条件の最大腐食速度をもって耐食性を評価した。その結果、従来技術の成分系では、低温、高温のいずれかの耐食性を改善することができても、全条件において満足すべき耐食性を得るのは困難であり、これを達成するには、従来技術の範疇を超えた成分設計が必要であることを知見した。
【０００７】
本発明において、主な役割を果たす合金元素は、Si，CuおよびSbの３元素である。図２において、前記４条件での最大腐食速度をSi，CuおよびSbの各含有量に対して整理する。これより、巨視的にはSi量が高くなると腐食速度が低下する傾向が読み取れるが、これは、SbおよびCuの両者が共存する場合に限られ、SbあるいはCuのいずれかが含有されない場合には、たとえSi量が多くとも低温、高温の全ての条件で満足すべき耐食性が得られない。
【０００８】
すなわち、単独添加では、いずれかの条件において有効であっても、全ての条件において目的とする耐食性を得るには至らず、所期の課題解決のためには、３元素の複合添加が必須であることを知見した。本発明では、Si，CuおよびSbの各必要量を、それぞれ、1.2 ％以上、0.05％以上、0.01％以上として規定した。
【０００９】
次に重要な元素はＣである。前記のSi，CuおよびSbの複合系において、Ｃ含有量を変化させた鋼材の腐食速度を図３に示す。これより、Ｃ量が不適切であると、いかに前記３元素の共同効果を活用しても、十分な耐食性は得られないことを知見した。本発明では、Ｃ量は少なくとも0.20％以下の低いレベルに抑制することとし、望ましい含有量は0.10％以下であり、さらに望ましくは0.010 ％以下である。
【００１０】
以上のように、本発明はSi，CuおよびSbの複合添加に加えて、低Ｃ化の要素を織り込むことによって、初めて、硫酸露点腐食環境における全温度条件で満足すべき耐食性を得たものであり、その要旨は以下のとおりである。
【００１１】
（１）質量％で、Ｃ：≦0.20％、Si： 1.2〜3.5 ％、Cu：0.05〜1.0 ％、Sb：0.01〜0.30％、Mn：≦1.0 ％、Ｐ：≦0.05％、Ｓ：≦0.05％、Al：≦0.10％、Ｎ：≦0.050 ％を含有し、残部Feおよび不可避的不純物からなることを特徴とする耐硫酸露点腐食性に優れた鋼。
【００１２】
（２）質量％で、Ｃ：≦0.10％、Si： 1.2〜3.5 ％、Cu：0.05〜1.0 ％、Sb：0.01〜0.30％、Mn： 0.2〜1.0 ％、Ｐ：≦0.05％、Ｓ：≦0.05％、Al：≦0.10％、Ｎ：≦0.020 ％を含有し、残部Feおよび不可避的不純物からなることを特徴とする耐硫酸露点腐食性に優れた鋼。
【００１３】
（３）質量％で、Ｃ：≦0.010 ％、Si： 1.2〜3.5 ％、Cu：0.05〜1.0 ％、Sb：0.01〜0.30％、Mn： 0.2〜1.0 ％、Ｐ：≦0.05％、Ｓ：≦0.05％、Al：≦0.10％、Ｎ：≦0.010 ％を含有し、残部Feおよび不可避的不純物からなることを特徴とする耐硫酸露点腐食性に優れた鋼。
【００１４】
（４）鋼成分として、質量％で、さらに、Mo：≦1.0 ％、Ni：≦0.5 ％、Nb：≦0.1 ％、Ｖ：≦0.1 ％、Ti：≦0.1 ％、Sn：0.01〜0.2 ％、Ｂ：0.0005〜0.010 ％の１種または２種以上を含むことを特徴とする（１），（２）または（３）記載の耐硫酸露点腐食性に優れた鋼。
【００１５】
（５）伝熱エレメントが（１）から（４）のいずれかの鋼からなることを特徴とする空気予熱器。
【００１６】
【発明の実施の形態】
本発明における鋼成分の限定理由について述べる。
【００１７】
Ｃ：Ｃは耐食性を劣化させるので、含有量は可及的低レベルが望ましく、特に0.20％を超える含有量では、低温、高温の両条件における耐食性を両立できなくなるため、上限を0.20％とした。なお、望ましい含有量は0.10％以下であり、さらに望ましくは0.010 ％以下である。
【００１８】
Si，Cu，Sb：低温、高温の両条件における良好な耐硫酸腐食性を確保するには３元素の共同効果を引き出すことが必須となる。このための各元素の必要最少含有量は、Si：1.2 ％、Cu：0.05％、Sb：0.01％である。これら元素の実用上の望ましい含有量の上限は以下のとおりである。
【００１９】
Siの上限：低温、高温の両条件で耐食性改善に有効な元素として可及的に多く含有させるのが望ましいが、3.5 ％を超えて含有させても耐食性改善効果は飽和するので、上限を3.5 ％とした。
【００２０】
Cuの上限：主として低温条件での耐食性改善に有効であるが、1.0 ％を超えて含有させると熱間加工性が劣化するため、上限を1.0 ％とした。
【００２１】
Sbの上限：低温条件の耐食性改善に有効であるが、多量に含有させると高温条件の耐食性が劣化すると共に熱間加工性が低下する。このため、上限を0.30％とした。
【００２２】
Mn：Mnは強化に有効な元素であり、本発明のような低Ｃ化による強度低下を補填する必要がある場合には適量を含有させる。望ましい含有量は0.2 ％以上であるが、1.0 ％を超えて含有させると耐食性が劣化するため、上限を1.0 ％とした。
【００２３】
Ｐ：精練過程で残留する不純物であり、0.05％を超えて残留すると耐食性が劣化するため、上限を0.05％とした。
【００２４】
Ｓ：Ｐと同様、不純物であり、0.05％を超えて残留すると熱間加工性、耐食性が劣化するため、上限を0.05％とした。
【００２５】
Al：精練過程において脱酸目的で含有させてもよいが、0.10％を超えて含有させると熱間加工性が劣化するので上限を0.10％とした。
【００２６】
Ｎ：Ｐ，Ｓと同様、不純物であり、可及的に低レベルが望ましく、上限を0.050 ％とする。望ましくは、0.020 ％以下、さらに望ましくは0.010 ％以下である。
【００２７】
本発明の鋼板は、以上の元素を基本成分とするが、これらの元素およびFeに加えて、さらなる耐食性改善、機械的特性の調整、熱間加工性改善の目的で、以下の元素を含有させてもよい。
【００２８】
Mo：強度の向上に有効であるが、低温条件における耐食性には望ましくないので1.0 ％以下が望ましい。
【００２９】
Ni：Cuの熱間加工性劣化を防止するために利用できるが、0.5 ％を超えて含有させると耐食性が劣化する傾向があるため、添加する場合は上限を0.5 ％として添加するのが望ましい。
【００３０】
Nb，Ｖ，Ti：析出物を形成して強靭化に有効な元素であるが、0.1 ％を超えて含有させると耐食性が劣化する傾向があるため、添加する場合は上限を0.1 ％として添加するのが望ましい。
【００３１】
Sn：耐食性改善に有効な元素であるが、0.01％未満では効果が発現せず、0.2 ％を超えると熱間加工性が劣化する傾向にあるため、添加する場合は、0.01〜0.2 ％とするのが望ましい。
【００３２】
Ｂ：Sb，Cu，Snといった耐食性改善元素を多量に含有させる場合に、熱間加工性の劣化を抑制することができる元素として有用である。0.0005％未満では十分な効果が得られず、0.010 ％を超えると、かえって熱間加工性が劣化する傾向があるため、添加する場合は、範囲を0.0005〜0.010 ％とするのが望ましい。
【００３３】
さらに、鋼板中には、上記耐食性、強度、加工性を劣化させない範囲で、例えば、Ｗ(0.5％以下で高温強度を改善する傾向がある）、Ca，Mg，REM(合計50ppm 以下で熱間加工性を改善する効果がある）等の他の付随的成分を含有させてもよい。
【００３４】
以下の組成からなる鋼は、通常の方法で溶製、鋳造された後、鍛造あるいは圧延といった通例の熱間加工方法によって板、管、棒、などの形状に加工されて実用に供することができる。さらに、必要に応じて熱間加工品に対して焼鈍などの熱処理を施しても良く、あるいは引き続いて酸洗を施した後、冷間加工を加えても良い。このような製造工程を経て得られる鋼材の耐食性は、工程条件によって影響されるものではなく、通常の炭素鋼鋼材と同様の工程で製造することが可能である。
【００３５】
以上の組成から成る鋼の用途としては、火力発電プラントにおけるボイラー周辺設備、化学プラントにおける硫酸精製設備や貯蔵タンク、製鉄プラントにおける酸洗槽などの硫酸環境で使用される多様な設備機器部材が挙げられるが、中でも事業用火力発電所や民生用ボイラーに付帯する空気予熱器の伝熱エレメント材には好適である。図４に空気予熱器の概要を示す。１の矢印は排ガスの流れ、２の矢印はボイラーに送り込む空気の流れ、３の矢印はローターの回転、４はローター、５はローター内に格納されたパスケット、６はパスケット内に装填される伝熱エレメント（波板形状に成形した鋼板を組み立てたもの）を意味する。伝熱エレメントに排ガスの顕熱を蓄積し、ボイラーに送り込む空気を予熱させる構造となっているが、この伝熱エレメントはSOX を含む排ガスに繰り返し曝されるため耐硫酸露点腐食性が重視される部材であり、本発明の用途として好適である。
【００３６】
【実施例】
表１に示す化学成分の鋼を真空溶解炉で陽性し50kgインゴットに鋳造した後、肉厚12mmまで熱間圧延した板材より、ｔ３ 20 40mmサイズの短冊試験片を採取して硫酸腐食試験を行った。硫酸露点腐食環境における低温域、高温域を代表する条件として、（ａ）40％硫酸、60℃、（ｂ）50％硫酸、80℃、（ｃ）80％硫酸、140 ℃、および、（ｄ）90％硫酸、160 ℃の４条件において４時間の浸漬試験を行い、腐食速度を求めた。
【００３７】
試験結果を表２に示す。これより、（ａ）〜（ｄ）のいずれかの条件における最大腐食速度は、比較例No．11〜18では、 145〜4890mg／ｍ2 ／hrであるのに対し、発明例No．１〜10では、60〜99ｇ／ｍ2 ／hrであり、明らかに優位にある。
【００３８】
また、４条件における腐食速度の最大値と最小値の差異も、発明鋼の方が、比較例に比べて小さく、温度や硫酸濃度の変化に対して腐食速度の変化が小さいという点でも、発明鋼は、プラント設計の自由度向上に寄与し得る。
【００３９】
なお、比較例No．11は、Sb含有量が本発明で規定する範囲を満たしておらず、No．12はＣ，Siの含有量、No．13はSi含有量、No．14はSi，Cu含有量、No．15はCu含有量、No．16はSi，Mn含有量、No．17はＣ含有量、No．18はSi，Cu，Sb含有量が、それぞれ、本発明で規定する範囲を外れているため、４条件のいずれかにおいて激しい腐食が生じる結果となった。
【００４０】
【表１】
【表２】
【発明の効果】
以上より、本発明によれば、低温から高温までの全ての硫酸露点腐食環境において優れた耐食性を発揮する鋼材が得られる。
【図面の簡単な説明】
【図１】 鋼材の硫酸露点腐食挙動を温度と硫酸濃度を指標として模式的に示した図である。
【図２】 硫酸露点腐食に及ぼすSi，CuおよびSbの影響を示す図である。縦軸の腐食速度は、（ａ）40％硫酸、60℃、（ｂ）50％硫酸、80℃、（ｃ）80％硫酸、140 ℃、（ｄ）90％硫酸、160 ℃の４条件における腐食速度の最大値を表示する。
【図３】 硫酸露点腐食に及ぼすＣの影響を示す図である。縦軸の腐食速度は、（ａ）40％硫酸、60℃、（ｂ）50％硫酸、80℃、（ｃ）80％硫酸、140 ℃、（ｄ）90％硫酸、160 ℃の４条件における腐食速度の最大値を表示する。
【図４】 空気予熱器の構造の概略を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a steel material excellent in sulfuric acid dew point corrosion resistance used in facilities such as flues, chimneys, boiler air preheaters and the like that are exposed to exhaust gas obtained by burning heavy oil, coal, garbage and the like.
[0002]
[Prior art]
When a fuel containing sulfur is burned, SO X is generated in the exhaust gas, which is combined with moisture in the exhaust gas to generate sulfuric acid. When the temperature of the exhaust gas decreases and the dew point of about 160 ° C. is reached, sulfuric acid gas condenses, and high concentration sulfuric acid with a sulfuric acid concentration of about 80 to 90% adheres to the steel material surface to cause corrosion. Further, when the temperature is lowered to about 80 ° C., water condensation is added to form sulfuric acid having a relatively low concentration of about 40 to 50% sulfuric acid, thereby accelerating corrosion. That is, as shown in FIG. 1, there are two conditions under which the steel material is corroded by the condensed sulfuric acid: a relatively high temperature and high concentration condition and a low temperature and low concentration condition.
[0003]
Conventionally, steel materials exhibiting corrosion resistance in a sulfuric acid environment have been developed to solve such a sulfuric acid dew point corrosion problem. For example, as disclosed in Japanese Patent Publication No. 43-14585, low alloy steels containing Sb and Cu, which are effective in resistance to sulfuric acid corrosion, have been put into practical use.
[0004]
However, the conventional steel does not achieve both corrosion resistance in the above-mentioned two corrosion conditions (around 160 ° C., 80-90% sulfuric acid condition and near 80 ° C., 40-50% sulfuric acid condition). For this reason, there is a problem that a plant that is frequently exposed to a cycle from high temperature to low temperature repeatedly starting and stopping does not necessarily exhibit the desired corrosion resistance.
[0005]
[Problems to be solved by the invention]
In view of the above situation, the present invention provides a steel material that can ensure excellent corrosion resistance in an environment of sulfuric acid dew point corrosion in all temperature ranges from high temperature to low temperature, and an air preheater using the same.
[0006]
[Means for Solving the Problems]
In response to the above-mentioned problems, the present inventors prepared test materials having various steel components, and the low temperature conditions were (a) 40% sulfuric acid, 60 ° C., (b) 50% sulfuric acid, 80 ° C. In addition, (c) 80% sulfuric acid, 140 ° C., (d) 90% sulfuric acid, 160 ° C., 2 conditions, a total of 4 corrosion tests were conducted, and corrosion resistance was evaluated with the maximum corrosion rate of 4 conditions. . As a result, in the component system of the prior art, it is difficult to obtain satisfactory corrosion resistance under all conditions even if the corrosion resistance of either low temperature or high temperature can be improved. It was found that component design beyond the scope of technology is necessary.
[0007]
In the present invention, the alloy elements that play a main role are the three elements Si, Cu and Sb. In FIG. 2, the maximum corrosion rate under the above four conditions is arranged for each content of Si, Cu and Sb. From this, it can be seen that when the amount of Si increases macroscopically, the corrosion rate tends to decrease, but this is limited to the case where both Sb and Cu coexist, and when either Sb or Cu is not contained. Even if the amount of Si is large, satisfactory corrosion resistance cannot be obtained under all conditions of low temperature and high temperature.
[0008]
In other words, even if it is effective under any condition, it does not lead to the desired corrosion resistance under all conditions, and a complex addition of three elements is indispensable for solving the desired problem. I found out that there was. In the present invention, the required amounts of Si, Cu, and Sb are respectively defined as 1.2% or more, 0.05% or more, and 0.01% or more.
[0009]
The next important element is C. FIG. 3 shows the corrosion rate of a steel material in which the C content is changed in the Si, Cu and Sb composite system. From this, it was found that if the amount of C is inappropriate, sufficient corrosion resistance cannot be obtained no matter how the joint effect of the three elements is utilized. In the present invention, the C content is suppressed to a low level of at least 0.20% or less, and the desirable content is 0.10% or less, and more desirably 0.010% or less.
[0010]
As described above, the present invention, for the first time, obtained satisfactory corrosion resistance under all temperature conditions in a sulfuric acid dew point corrosion environment by incorporating a low C element in addition to the combined addition of Si, Cu and Sb. Yes, the summary is as follows.
[0011]
(1) By mass%, C: ≦ 0.20%, Si: 1.2-3.5%, Cu: 0.05-1.0%, Sb: 0.01-0.30%, Mn: ≦ 1.0%, P: ≦ 0.05%, S: ≦ 0.05 %, Al: ≦ 0.10%, N: ≦ 0.050%, comprising the balance Fe and inevitable impurities, and having excellent resistance to sulfuric acid dew point corrosion.
[0012]
(2) By mass%, C: ≦ 0.10%, Si: 1.2 to 3.5%, Cu: 0.05 to 1.0%, Sb: 0.01 to 0.30%, Mn: 0.2 to 1.0%, P: ≦ 0.05%, S: ≦ A steel excellent in sulfuric acid dew point corrosion resistance characterized by containing 0.05%, Al: ≦ 0.10%, N: ≦ 0.020%, and the balance Fe and unavoidable impurities .
[0013]
(3) By mass%, C: ≦ 0.010%, Si: 1.2-3.5%, Cu: 0.05-1.0%, Sb: 0.01-0.30%, Mn: 0.2-1.0%, P: ≦ 0.05%, S: ≦ Steel excellent in sulfuric acid dew point corrosion resistance, characterized by containing 0.05%, Al: ≦ 0.10%, N: ≦ 0.010%, and the balance consisting of Fe and inevitable impurities .
[0014]
(4) As a steel component, in mass%, Mo: ≦ 1.0%, Ni: ≦ 0.5%, Nb: ≦ 0.1%, V: ≦ 0.1%, Ti: ≦ 0.1%, Sn: 0.01 to 0.2%, B: Steel excellent in sulfuric acid dew point corrosion resistance according to (1), (2) or (3), characterized by containing one or more of 0.0005 to 0.010%.
[0015]
(5) An air preheater, wherein the heat transfer element is made of any one of steels (1) to (4).
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The reason for limiting the steel components in the present invention will be described.
[0017]
C: Since C deteriorates corrosion resistance, it is desirable that the content is as low as possible. In particular, when the content exceeds 0.20%, it becomes impossible to achieve both low temperature and high temperature corrosion resistance, so the upper limit was made 0.20%. . The desirable content is 0.10% or less, and more desirably 0.010% or less.
[0018]
Si, Cu, Sb: To ensure good sulfuric acid corrosion resistance under both low and high temperature conditions, it is essential to bring out the joint effect of the three elements. The required minimum content of each element for this purpose is Si: 1.2%, Cu: 0.05%, Sb: 0.01%. The upper limit of practically desirable contents of these elements is as follows.
[0019]
Upper limit of Si: It is desirable to contain as much as possible as an element effective in improving corrosion resistance under both low temperature and high temperature conditions, but even if it exceeds 3.5%, the effect of improving corrosion resistance is saturated, so the upper limit is set to 3.5 %.
[0020]
Upper limit of Cu: mainly effective for improving corrosion resistance under low temperature conditions, but if the content exceeds 1.0%, hot workability deteriorates, so the upper limit was made 1.0%.
[0021]
Upper limit of Sb: Effective for improving the corrosion resistance under low temperature conditions, but if contained in a large amount, the corrosion resistance under high temperature conditions deteriorates and hot workability deteriorates. For this reason, the upper limit was made 0.30%.
[0022]
Mn: Mn is an element effective for strengthening, and is contained in an appropriate amount when it is necessary to compensate for the strength reduction due to low C as in the present invention. The desirable content is 0.2% or more, but if it exceeds 1.0%, the corrosion resistance deteriorates, so the upper limit was made 1.0%.
[0023]
P: An impurity remaining in the scouring process, and if it exceeds 0.05%, the corrosion resistance deteriorates, so the upper limit was made 0.05%.
[0024]
Like S: P, it is an impurity, and if it exceeds 0.05%, hot workability and corrosion resistance deteriorate, so the upper limit was made 0.05%.
[0025]
Al: It may be contained for the purpose of deoxidation in the scouring process, but if it exceeds 0.10%, the hot workability deteriorates, so the upper limit was made 0.10%.
[0026]
N: Like P and S, it is an impurity, and it is desirable that the level be as low as possible. Desirably, it is 0.020% or less, more desirably 0.010% or less.
[0027]
The steel sheet of the present invention contains the above elements as basic components. In addition to these elements and Fe, the steel sheet contains the following elements for the purpose of further improving corrosion resistance, adjusting mechanical properties, and improving hot workability. May be.
[0028]
Mo : Effective for improving strength, but is not desirable for corrosion resistance under low temperature conditions, so 1.0% or less is desirable.
[0029]
Ni: Cu can be used to prevent hot workability deterioration, but if it exceeds 0.5%, the corrosion resistance tends to deteriorate. Therefore, when it is added, it is desirable to add it at an upper limit of 0.5%.
[0030]
Nb, V, Ti: These elements are effective for toughening by forming precipitates, but if added over 0.1%, the corrosion resistance tends to deteriorate, so if added, the upper limit should be 0.1% Is desirable.
[0031]
Sn: An element effective for improving corrosion resistance. However, if it is less than 0.01%, the effect does not appear, and if it exceeds 0.2%, the hot workability tends to deteriorate. Is desirable.
[0032]
B: Useful as an element that can suppress deterioration of hot workability when a large amount of corrosion resistance improving elements such as Sb, Cu, and Sn is contained. If it is less than 0.0005%, a sufficient effect cannot be obtained, and if it exceeds 0.010%, hot workability tends to deteriorate. Therefore, when it is added, the range is preferably 0.0005 to 0.010%.
[0033]
Furthermore, in steel sheets, the above corrosion resistance, strength, and workability are not degraded. For example, W (which tends to improve high-temperature strength at 0.5% or less), Ca, Mg, REM (total 50ppm or less at hot Other ancillary components such as an effect of improving processability may be contained.
[0034]
Steel having the following composition is melted and cast by a normal method, and then processed into a shape of a plate, a pipe, a rod, etc. by a usual hot working method such as forging or rolling, and can be put to practical use. . Further, if necessary, the hot-worked product may be subjected to a heat treatment such as annealing, or may be subsequently pickled and then cold-worked. The corrosion resistance of the steel material obtained through such a manufacturing process is not affected by the process conditions, and can be manufactured in the same process as a normal carbon steel material.
[0035]
Applications of steel with the above composition include various equipment equipment used in sulfuric acid environments such as boiler peripheral equipment in thermal power plants, sulfuric acid refining equipment and storage tanks in chemical plants, and pickling tanks in steel manufacturing plants. However, it is particularly suitable for a heat transfer element material of an air preheater attached to a commercial thermal power plant or a consumer boiler. FIG. 4 shows an outline of the air preheater. 1 indicates the flow of exhaust gas, 2 indicates the flow of air sent to the boiler, 3 indicates the rotation of the rotor, 4 indicates the rotor, 5 indicates the patquet stored in the rotor, and 6 indicates the transmission loaded in the patquet. It means a thermal element (an assembly of steel plates formed into corrugated sheets). The sensible heat of the exhaust gas is accumulated in the heat transfer element and the air sent to the boiler is preheated. However, since this heat transfer element is repeatedly exposed to the exhaust gas containing SO X , sulfuric acid dew point corrosion resistance is emphasized. This is a member suitable for use in the present invention.
[0036]
【Example】
After stripping the steel of chemical composition shown in Table 1 in a vacuum melting furnace and casting it into a 50kg ingot, a strip test piece of t3 20 40mm size was collected from a plate hot-rolled to a thickness of 12mm and subjected to a sulfuric acid corrosion test. It was. Conditions representative of the low temperature range and high temperature range in a sulfuric acid dew point corrosion environment include: (a) 40% sulfuric acid, 60 ° C, (b) 50% sulfuric acid, 80 ° C, (c) 80% sulfuric acid, 140 ° C, and (d ) A 4-hour immersion test was performed under four conditions of 90% sulfuric acid and 160 ° C. to determine the corrosion rate.
[0037]
The test results are shown in Table 2. From this, the maximum corrosion rate under any of the conditions (a) to (d) is as shown in Comparative Example No. In the case of 11 to 18, it is 145 to 4890 mg / m 2 / hr. In 1-10, it is 60-99 g / m < 2 > / hr, and there exists a clear advantage.
[0038]
In addition, the difference between the maximum value and the minimum value of the corrosion rate under the four conditions is also smaller in the invention steel than in the comparative example, and the change in the corrosion rate is small with respect to the change in temperature and sulfuric acid concentration. Steel can contribute to the improvement of plant design flexibility.
[0039]
Comparative Example No. No. 11 does not satisfy the range specified by the present invention for the Sb content. 12 is the content of C and Si. 13 is the Si content, No. 14 is Si, Cu content, No. 14 15 is the Cu content, No. 16 is Si, Mn content, No. 17 is C content, No. In No. 18, the Si, Cu, and Sb contents were out of the range specified in the present invention, and therefore severe corrosion occurred in any of the four conditions.
[0040]
[Table 1]
[Table 2]
【The invention's effect】
As described above, according to the present invention, a steel material exhibiting excellent corrosion resistance in all sulfuric acid dew point corrosion environments from low temperature to high temperature can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing the sulfuric acid dew point corrosion behavior of a steel material using temperature and sulfuric acid concentration as indices.
FIG. 2 is a diagram showing the influence of Si, Cu and Sb on sulfuric acid dew point corrosion. The corrosion rate on the vertical axis is (a) 40% sulfuric acid, 60 ° C, (b) 50% sulfuric acid, 80 ° C, (c) 80% sulfuric acid, 140 ° C, (d) 90% sulfuric acid, 160 ° C. Displays the maximum value of the corrosion rate.
FIG. 3 is a diagram showing the influence of C on sulfuric acid dew point corrosion. The corrosion rate on the vertical axis is (a) 40% sulfuric acid, 60 ° C, (b) 50% sulfuric acid, 80 ° C, (c) 80% sulfuric acid, 140 ° C, (d) 90% sulfuric acid, 160 ° C. Displays the maximum value of the corrosion rate.
FIG. 4 is a diagram schematically showing the structure of an air preheater.
Claims (5)
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001027455 | 2001-02-02 | ||
| JP2001027455 | 2001-02-02 | ||
| PCT/JP2002/000856 WO2002063056A1 (en) | 2001-02-02 | 2002-02-01 | Steel excellent in resistance to sulfuric acid dew point corrosion and preheater for air |
Publications (2)
| Publication Number | Publication Date |
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| JPWO2002063056A1 JPWO2002063056A1 (en) | 2004-06-10 |
| JP4291573B2 true JP4291573B2 (en) | 2009-07-08 |
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| Application Number | Title | Priority Date | Filing Date |
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| JP2002562790A Expired - Lifetime JP4291573B2 (en) | 2001-02-02 | 2002-02-01 | Steel and air preheater with excellent resistance to sulfuric acid dew point corrosion |
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| Country | Link |
|---|---|
| JP (1) | JP4291573B2 (en) |
| KR (1) | KR100511653B1 (en) |
| CN (1) | CN1195883C (en) |
| TW (1) | TW554051B (en) |
| WO (1) | WO2002063056A1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP4319817B2 (en) | 2001-11-19 | 2009-08-26 | 新日本製鐵株式会社 | Low alloy steel excellent in hydrochloric acid corrosion resistance and sulfuric acid corrosion resistance and its welded joint |
| JP4823930B2 (en) * | 2006-02-10 | 2011-11-24 | 新日本製鐵株式会社 | Acid corrosion resistant steel |
| JP5186769B2 (en) * | 2006-02-13 | 2013-04-24 | 新日鐵住金株式会社 | Sulfuric acid dew-point corrosion steel |
| KR100946148B1 (en) | 2006-11-21 | 2010-03-10 | 주식회사 포스코 | Steel excellent in resistance to corrosion by sulfuric acid and method for manufacturing the same |
| CN100419115C (en) * | 2006-11-23 | 2008-09-17 | 武汉钢铁(集团)公司 | Ultrahigh-strength atmospheric-corrosion resistant steel |
| CN101775544B (en) * | 2010-03-03 | 2011-09-14 | 武钢集团昆明钢铁股份有限公司 | Rolling method of sulfuric acid dew point corrosion-resistant steel KNS |
| CN101892433A (en) * | 2010-06-25 | 2010-11-24 | 南京钢铁股份有限公司 | Low-alloy steel with low-temperature sulfuric acid dew point corrosion resistance |
| CN101921966B (en) * | 2010-08-19 | 2011-12-21 | 攀钢集团钢铁钒钛股份有限公司 | Production method of sulfuric acid dew-point corrosion resistance hot rolled sheet |
| US20150299829A1 (en) * | 2012-03-19 | 2015-10-22 | Nisshin Steel Co., Ltd. | Acid dew point corrosion-resistant steel and exhaust gas flow path constituent member |
| CN103589972B (en) * | 2013-10-10 | 2015-04-29 | 中天钢铁集团有限公司 | Low-cost low alloy steel for resistance to dew point corrosion of sulfuric acid as well as production process and application of low alloy steel |
| CN104357754B (en) * | 2014-10-17 | 2016-06-22 | 江阴兴澄特种钢铁有限公司 | A kind of corrosionproof steel against sulfuric acid at dew point plate and manufacture method thereof |
| CN104831172A (en) * | 2015-04-23 | 2015-08-12 | 苏州劲元油压机械有限公司 | Manufacturing method of fixing plate for hydraulic pressure station |
| CN106556018A (en) * | 2016-10-25 | 2017-04-05 | 安徽沃木采暖科技有限公司 | Suitable for the fireplace chimneys of firewood fuel |
| CN106568094A (en) * | 2016-10-25 | 2017-04-19 | 安徽沃木采暖科技有限公司 | Chimney for natural gas fireplace |
| CN106568096A (en) * | 2016-10-25 | 2017-04-19 | 安徽沃木采暖科技有限公司 | Anti-corrosion fireplace chimney |
| CN106500119A (en) * | 2016-10-25 | 2017-03-15 | 安徽沃木采暖科技有限公司 | The special chimney of coal fireplace |
| CN108660384A (en) * | 2017-03-30 | 2018-10-16 | 宝山钢铁股份有限公司 | A kind of low-alloy steel of sulfuric acid corrosion resistant, steel pipe, steel plate and its manufacturing method |
| KR101977471B1 (en) | 2017-07-17 | 2019-05-10 | 한국동서발전(주) | Apparatus and method for controlling temperature of air preheater cold side |
| CN109652745A (en) * | 2019-03-01 | 2019-04-19 | 江苏建中新材料科技有限公司 | A kind of acidproof heat exchanger tube steel and its processing technology |
| CN109916807A (en) * | 2019-03-28 | 2019-06-21 | 长沙理工大学 | A kind of simulation gas generating processes for studying corrosion of sulfuric acid at dew point |
| CN109916809A (en) * | 2019-03-28 | 2019-06-21 | 长沙理工大学 | A kind of dew point corrosion simulator applied to combustion engine power station waste heat boiler |
| CN112575269A (en) * | 2019-09-27 | 2021-03-30 | 宝山钢铁股份有限公司 | Low-temperature acid dew point corrosion resistant cold-rolled steel and manufacturing method thereof |
| CN110904384B (en) * | 2019-12-02 | 2021-04-06 | 中国石油天然气集团有限公司 | Q345NS spiral submerged arc welded pipe for resisting sulfuric acid dew point corrosion and manufacturing process thereof |
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| JPS4937172B1 (en) * | 1969-06-25 | 1974-10-07 | ||
| JPH11350081A (en) * | 1998-06-11 | 1999-12-21 | Nippon Steel Corp | Corrosion resistant steel |
| JP2000017382A (en) * | 1998-07-03 | 2000-01-18 | Nippon Steel Corp | Steel excellent in sulfuric acid corrosion resistance |
| JP2000073138A (en) * | 1998-08-26 | 2000-03-07 | Nkk Corp | Steel for bolt excellent in sulfuric acid corrosion- resistance |
| JP2000073139A (en) * | 1998-08-26 | 2000-03-07 | Nkk Corp | Steel for bolt excellent in sulfuric acid corrosion resistance |
| JP2002047538A (en) * | 2000-07-27 | 2002-02-15 | Nkk Corp | Rolled shape having excellent earthquake resistance and sulfuric acid resistance, and its manufacturing method |
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| CN1195883C (en) | 2005-04-06 |
| TW554051B (en) | 2003-09-21 |
| KR100511653B1 (en) | 2005-09-01 |
| CN1455822A (en) | 2003-11-12 |
| JPWO2002063056A1 (en) | 2004-06-10 |
| WO2002063056A1 (en) | 2002-08-15 |
| KR20020093882A (en) | 2002-12-16 |
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