JPS591658A - Corrosion-and heat-resistant steel for boiler tube - Google Patents

Abstract

PURPOSE:To obtain a steel for a boiler tube with superior corrosion resistance, heat resistance and toughness, by adding specified percentages of C, Si, Mn, Cr, Ni and N to Fe and by regulating the austenite stabilizing index to a specified range. CONSTITUTION:A steel consisting of, by weight, 0.02-0.12% C, 1.7-3.5% Si, 0.5-2.5% Mn, 15.0-26.0% Cr, 10.0-30.0% Ni, 0.10-0.25% N and the balance Fe with inevitable impurities and having -1-3 austenite stabilizing index ASI expressed by the equation is prepared. <=1.0% Nb, >=1.0% Ti (Nb+Ti <=1.0%), <=0.01% B, <=0.1% Al and <=0.05% Ca may be added to the steel. Thus, a steel for a boiler tube ensuring corrosion and heat resistances at high temp. and toughness after long-time use is obtd.

Description

【発明の詳細な説明】 本発明は石炭燃焼、重油燃焼雰囲気における高温度での
耐食性に優れ、かつ強度が高いとともに高温度に長時間
さらされた後にも−高い靭性を有するがイラチューブ用
耐食耐熱用鋼に関するものである。Detailed Description of the Invention The present invention provides corrosion resistance for flat tubes that have excellent corrosion resistance at high temperatures in coal combustion and heavy oil combustion atmospheres, and have high strength and high toughness even after being exposed to high temperatures for long periods of time. This relates to heat-resistant steel.

近年エネルギー資源の供給不安定による高騰が続いてお
り、省資源、省エネルギー化が叫ばれ、産業用設備はこ
の流れに従い改良される傾向にある。火力発電設備にお
いてもこの傾向は顕著であり、蒸気条件を高温高圧化す
ることにより熱効率の改善を図り、高性能火力発電設備
へと移行する動向にある。すなわち現状の蒸気条件は５
３８℃、２４５　ｋｇ／ｃＩｎ”が採用されているが、
これを６５０℃、３５０ｋｇ々−に改善することが考え
られている。しかしこのためには現状の火力発電用がイ
ラチューブに用いられているＳＵＳ　３２１　ＨＴＢ　
、　５ＵＳ３４７ＨＴＢではその特性が高温強度及び筒
部耐食性の観点から不十分であり、新規な材料の開発が
切に望まれている。In recent years, prices have continued to rise due to the unstable supply of energy resources, and resource and energy conservation has been called for, and industrial equipment has tended to be improved in accordance with this trend. This trend is also noticeable in thermal power generation equipment, and there is a trend toward improving thermal efficiency by raising the steam conditions to higher temperatures and pressures, and moving toward high-performance thermal power generation equipment. In other words, the current steam condition is 5
38℃, 245 kg/cIn” is adopted,
It is being considered to improve this to 650°C and 350 kg. However, for this purpose, SUS 321 HTB, which is currently used for the Iratube for thermal power generation, is required.
, 5US347HTB has insufficient properties in terms of high temperature strength and cylindrical corrosion resistance, and the development of a new material is strongly desired.

本発明はかかる動向を賀歌に開発されたもので、高温度
での耐食性、耐熱性と長時間使用後の靭性を確保した全
く新しい型のがイラチューブ用鋼である。The present invention was developed in recognition of this trend, and is a completely new type of steel for flat tubes that ensures corrosion resistance at high temperatures, heat resistance, and toughness after long-term use.

一般に高温度の空気中においてＣｒの耐酸化性が優れて
おり、耐食耐熱用鋼として高Ｃｒ化が計られている。本
３明は火力発電燃焼雰囲気中において従来の知見に反し
、１５．０〜２６．０％の範囲内でのＣｒ含ｉｎの差は
耐食性にほとんど影響を与えないこと全知見し、この雰
囲気において、耐食性を向上させるだめの唯一の元素と
してＳＩを見い出したことに基づいている。すなわちＳ
ｌを１．７チ以上添加すると添加量が増すにつれ耐食性
が飛躍的に向上する。しかし周知のように鋼中のＳＩ含
Ｍ鎗を増加させて行くとσ相が生成し、高温強度が低下
する。壕だ長時間高温にさらしだ後靭性が著しく低下す
るため長時間の使用にあたっては信頼性の点で問題があ
った。本発明ではとのσ相生成を回避するための新しい
知見を得、ＡＳＩ（オーステナイト安定化指数）という
概念を導入Ｌ％　８１の有効利用範囲を拡大し、耐食性
耐熱性及び使用後靭性の面から信頼性の高い＋３”イラ
チューブ用耐食耐熱用鋼を開発したものである。Generally, Cr has excellent oxidation resistance in high-temperature air, and efforts are being made to increase the Cr content as corrosion-resistant and heat-resistant steel. The present study found that, contrary to conventional knowledge, the difference in Cr content within the range of 15.0 to 26.0% has little effect on corrosion resistance in the combustion atmosphere of thermal power generation. This is based on the discovery of SI as the only element that improves corrosion resistance. That is, S
When 1.7 or more liters are added, corrosion resistance improves dramatically as the amount added increases. However, as is well known, when the SI-containing M-containing steel is increased, a σ phase is generated and the high-temperature strength is reduced. After being exposed to high temperatures for a long period of time, the toughness of the trench deteriorates significantly, so there was a problem with reliability during long-term use. In the present invention, we have obtained new knowledge to avoid the formation of σ phase with and introduced the concept of ASI (Austenite Stabilization Index), expanding the range of effective use of L%81, and improving the corrosion resistance, heat resistance, and toughness after use. We have developed a highly reliable corrosion-resistant and heat-resistant steel for +3" flat tubes.

ＡＳＩはオーステナイトマトリッークスの安定性を示す
指針でマ）　ＩＪソックス安定であればσ相等異相の金
属間化合物が生成し難くなる。ＡＳＩＫ彰響を及ぼす元
素としてＣ、Ｎｌ　、　Ｍｎ　＋’　Ｎ　ｒ　Ｃｒ　＃
　Ｓｌが知見されそれら元素の効果を総合的に検討した
結果、Ａ、ＳＩを以下の ＡＳＩ　＝　（２１Ｃ＋Ｎｌ　＋’＋１．５Ｍｎ＋１１
．５Ｎ＋７　）−（３Ｓｌ＋Ｃｒ）式で現わした場合に
、高温強度及び使用後靭性に対する元素効果を良く整理
出来ることを見出した。ASI is a guideline that indicates the stability of the austenitic matrix.) If the IJ socks are stable, intermetallic compounds of different phases such as σ phase will be difficult to form. C, Nl, Mn +' N r Cr # as elements that affect ASIK
As a result of the discovery of Sl and the effects of these elements, A and SI were changed to the following ASI = (21C+Nl +'+1.5Mn+11
．． It has been found that elemental effects on high-temperature strength and post-use toughness can be well organized when expressed by the formula 5N+7)-(3Sl+Cr).

すなわちＡＳＩが−１〜３の範囲で最も高温強度及び高
温長時間時効後の靭性が高い。That is, when the ASI is in the range of -1 to 3, the high-temperature strength and the toughness after high-temperature long-term aging are the highest.

以下に本発明における各成分元素を限定した理由につい
て述べる。The reasons for limiting each component element in the present invention will be described below.

Ｓｌは第１図に示すように添加量が増加するに従って人
工灰（４１％　Ｎａ２５ｏ４＋　５１％［ｉ’ｅ　２　
（Ｓｎ４　）　５　＋８９６　Ｖ２ｏ５）中、６５０℃
×２βｏｈ腐食後のｇ素置が減少する。従来ＳＵＳ　３
４７　ＨＴＢ等が用いられている５３８℃においてはこ
の腐食減量が約３５０ｍ９／ｃｒｎ２であることがら、
６５０℃においても実用的に３５０ψ讐以下の腐食減量
を確保することが必要と考えられる。従って本発明にお
いては８１の下限を１．７０％とした。これ以上のＳｌ
を添加して行けば行くほど耐食性は向上するが、ｓｌは
前述のように強力なσ相生成元素であり、このσ相の生
成を抑制するためにＡＳＩ値を制御する必要があるが、
ＡＳＩの式中８１の増加に伴いバランスが大きくずれる
とＣ、Ｍｎ’、　Ｎでは制御出来ずＮ１を添加してバラ
ンスを保つ必要が生じてくる。このため過度の添加は工
業的経済性をそこなうことになる。従って８１の上限を
３．５優に限定した。この中でも好ましいｓｉの含ｉｔ
は２．１〜３．０％の範囲にある。又さらに最も効果的
な含肩量は２．６〜３．０係の範囲である。As shown in Figure 1, as the added amount increases, Sl becomes artificial ash (41% Na25o4+ 51%
(Sn4) 5 +896 V2o5), 650°C
×2βohThe g element after corrosion decreases. Conventional SUS 3
47 At 538°C, where HTB etc. are used, this corrosion loss is about 350 m9/crn2.
It is considered necessary to practically ensure a corrosion loss of 350 ψ or less even at 650°C. Therefore, in the present invention, the lower limit of 81 is set to 1.70%. No more SL
Corrosion resistance improves as sl is added, but as mentioned above, sl is a strong σ-phase forming element, and it is necessary to control the ASI value to suppress the formation of this σ phase.
If the balance deviates greatly as 81 increases in the ASI formula, it cannot be controlled with C, Mn', and N, and it becomes necessary to maintain the balance by adding N1. Therefore, excessive addition will impair industrial economy. Therefore, the upper limit of 81 was limited to 3.5 well. Among these, preferable si content is
is in the range of 2.1-3.0%. Furthermore, the most effective shoulder content is in the range of 2.6 to 3.0.

また第２図に示すようにＡＳＩが−１〜３の範囲で７０
０℃、１０００ｈ時効後の靭性が高い。ＡＳＩがマイナ
ス側から０に近づくＫつれてσ相生成は減少し０になる
。従ってＡＳＩがＯに近づくにつれて靭性は向上する。Also, as shown in Figure 2, ASI is 70 in the range of -1 to 3.
High toughness after aging at 0°C for 1000 hours. As ASI approaches 0 from the negative side, σ phase generation decreases to 0. Therefore, as the ASI approaches O, the toughness improves.

一方ＡＳＩが０以上の場合σ相は生成されないが粒界に
析出するＭ２３Ｃ６１ｉが増加し、ＡＳＩが増加するに
従い、靭性は低下する。しかしマトリ、クス自体が延性
をもって−いるためにＡＳＩが一７以下で靭性がほぼ０
に近くなるのに比べ、ＡＳＩが０以上の場合はＶ　Ｅ２
０が約５ｋｇ・ｍで飽和している。本発明においては工
業的見地からｖＥ２ｏが７ｋｇ・ｍ以上あれば良いと考
えられＡＳＩの範囲を−１〜３とした。しかしもっと長
時間の時効においてさらにＶ　Ｅ２　ｏが低下する可能
性が有り、最も望ましくはＡＳｒが−０，５〜２の範囲
にある。On the other hand, when ASI is 0 or more, no σ phase is generated, but M23C61i precipitates at grain boundaries increases, and as ASI increases, toughness decreases. However, since matrices and clays themselves have ductility, when the ASI is 17 or less, the toughness is almost 0.
When ASI is 0 or more, V E2
0 is saturated at approximately 5 kg/m. In the present invention, from an industrial standpoint, it is considered that vE2o of 7 kg·m or more is sufficient, so the ASI range is set to -1 to 3. However, there is a possibility that V E2 o will further decrease during aging for a longer time, and most preferably, ASr is in the range of -0.5 to 2.

Ｃは高温強度を保持するために下段を０．０２％とした
。また過度の添加は炭化物の析出量を増大せしめ時効後
の靭性を低下させるため上限を０．１２％とした。C was set at 0.02% in the lower row to maintain high-temperature strength. Moreover, excessive addition increases the amount of carbide precipitation and reduces toughness after aging, so the upper limit was set at 0.12%.

Ｍｎの下限は通常鋼中に含有されるＳを固定するに足り
る電として０．５％にしだ。又Ｍｎは耐食性、高温強度
及び靭性に対しＡＳＩにより影響する。すなわちＡＳＩ
を調整するためにＮ１の代りに安価な元素としてＭｎを
添加するが、過度の添加は溶製上のトラブル、熱間加工
上のトラグルを生じ、かえって経済性をそこなう。この
ため上限を２．５チとしだ。The lower limit of Mn is usually 0.5%, which is sufficient to fix S contained in steel. Mn also influences corrosion resistance, high temperature strength and toughness through ASI. That is, ASI
Mn is added as an inexpensive element in place of N1 in order to adjust the temperature, but excessive addition causes trouble in melting and trouble in hot working, which actually impairs economic efficiency. For this reason, the upper limit is set at 2.5 inches.

Ｎｌは高温強度、靭性を向上させる。本発明においては
６５０℃で使用する場合に、従来の５ＵＳ３４７　ＨＴ
Ｂ以上の強度が必要であり、下限を１０．０チとした。Nl improves high temperature strength and toughness. In the present invention, when used at 650°C, conventional 5US347 HT
A strength of B or higher is required, and the lower limit was set at 10.0 inches.

Ｎｉ量を増量して行くと高温強度、靭性は向上するので
多量の添加が望ましいがＡＳＩ値で規定され上限は３０
．０１以下である。Increasing the amount of Ni improves high temperature strength and toughness, so it is desirable to add a large amount, but the upper limit is 30 as specified by the ASI value.
．． 01 or less.

Ｃｒは前述したように人工灰中６５０℃での耐食性には
ほとんど効果がないことから高温強度及び靭性の面から
は少い方が好ましいと考えられるが、デイラチューブの
場合内面に流れる水、水蒸気等による腐食を考え通常の
５ＵＳ３０４　、３２１　。As mentioned above, Cr has almost no effect on corrosion resistance in artificial ash at 650°C, so from the viewpoint of high-temperature strength and toughness, a small amount of Cr is considered preferable. Considering the corrosion caused by etc., the normal 5US304, 321.

３４７．３１６等オーステナイトステンレス鋼の含有す
るレベルとした。すなわち下限を１５．０％、上限を２
６．０％とした。The level was set to include austenitic stainless steel such as 347.316. In other words, the lower limit is 15.0% and the upper limit is 2.
It was set at 6.0%.

Ｎは通常低温度域での強度を向上させるが、高温度域で
はその効果が少く、むしろ逆にクリープ強度を低下させ
るという報告もある。しかし本発明の鋼においてはＮは
７００℃におけるクリープ強度を向上させる効果を有し
ており、その効果が顕著に現われる値０．１係を下限と
した。又Ｎ量が増加すると窒化物を多量に生成し、かえ
って靭性を低下せしめると同時に他の特性−例えば溶接
性等を劣化させるため望ましくなく上限を０．２５％と
した。Although N usually improves strength in a low temperature range, there are also reports that this effect is less in a high temperature range, and that it actually reduces creep strength. However, in the steel of the present invention, N has the effect of improving the creep strength at 700°C, and the lower limit was set to a value of 0.1, at which this effect becomes noticeable. Furthermore, if the amount of N increases, a large amount of nitrides will be produced, which will actually lower the toughness and at the same time deteriorate other properties such as weldability, which is not desirable and the upper limit was set at 0.25%.

上述の主要元素のほかに必要に応じて以下の成分元素を
添加することができる。In addition to the above-mentioned main elements, the following component elements can be added as necessary.

Ｎｂ及びＴＩは炭窒化物形成効果があり、本発明におい
てもＮｂ及びＴＩを添加して行くと、その量に従い鋼中
のＣ，Ｎを固定し、微細分散させることからクリープ強
度が向上する。しかしこれらの添加元素を増大すると高
温戻で粗大な窒化物が生成し、鋼中のＭ効Ｃ及びＮ駄を
減じると同時に加工性、溶接性の面で好ましくない。従
ってそれぞれの添７ＪＤ童の最大を１．Ｃ１とし、Ｎｂ
＋ＴＩの場合もａ甥においても１．０チと限定した。Nb and TI have the effect of forming carbonitrides, and in the present invention, when Nb and TI are added, C and N in the steel are fixed and finely dispersed according to the amount, thereby improving creep strength. However, if the content of these additive elements is increased, coarse nitrides will be formed during high-temperature return, which will reduce the M effect, C and N in the steel, and at the same time be unfavorable in terms of workability and weldability. Therefore, the maximum for each of the 7 JD children is 1. C1, Nb
In the case of +TI and a-nephew, it was limited to 1.0 chi.

Ｂの添刀口は高温強度を改善することを目的に添加され
る。多量の添加は硼化物の生成、溶接性の低下をきたし
、好ましくなく、溶接性の低下が致命的にならない範囲
とし上限を０．０１％に限定した。B is added for the purpose of improving high temperature strength. Addition of a large amount causes the formation of borides and a decrease in weldability, which is undesirable.The upper limit was set at 0.01% so that the decrease in weldability would not become fatal.

Ａｔ及びＣｍは鋼中の脱酸元素としてその１種もしくは
両者を添加する。Ａｔは高温耐食性を向上させる効果が
あるといわれているが、本発明においてはその効果が明
らかでない。従ってＡｔはＣａと同様に脱酸元素として
添加し本発明鋼の製品の健全性を向上させるため通常鋼
の製造範囲における脱酸量を添加する。従って上限をＡ
ｔ　０．１　％、Ｃａ　Ｏ，０，５ｑ６とした。At or both of At and Cm are added as deoxidizing elements in the steel. Although At is said to have the effect of improving high-temperature corrosion resistance, this effect is not clear in the present invention. Therefore, like Ca, At is added as a deoxidizing element, and in order to improve the soundness of the steel product of the present invention, the deoxidizing amount is added within the manufacturing range of ordinary steel. Therefore, the upper limit is A
t 0.1%, Ca O, 0.5q6.

以下に実施力をもって説明する。This will be explained in terms of practicality below.

第１表に成分を示した鋼のＡ−Ｈは本発明鋼で■〜Ｐは
比較鋼である。Ｓ１含有量の低い！鋼ではＡＳＩは満足
しているが、耐食性が著しく悪い。Of the steels whose components are shown in Table 1, A to H are the steels of the present invention, and ■ to P are comparative steels. Low S1 content! Steel has a satisfactory ASI, but its corrosion resistance is extremely poor.

本発明の一つの特徴は耐食性に有り、Ｊ−Ｐの比較鋼に
おいては耐食性を付与するために本発明の８１の範囲内
で製造した。しかし、本発明鋼Ａ−Ｈとそれぞれ比較す
るとＡＳＩが適切でないためにクリープ破断時間及び時
効後靭性が著しく低いことがわかり、本発明鋼の優位性
が明らかである。One feature of the present invention is corrosion resistance, and the comparative steel of J-P was manufactured within the range of 81 of the present invention in order to impart corrosion resistance. However, when compared with the steels of the present invention A to H, it was found that the creep rupture time and toughness after aging were extremely low due to inappropriate ASI, and the superiority of the steels of the present invention is clear.

本発明鋼は通常オーステナイトステンレス鋼の製造され
る工程において製造される。すなわち電炉、転炉その他
の通常の溶製法が採用出来、鋼塊に鋳込み分塊工程を通
るか、連鋒鋳造によりビレットを製造し、熱間押出しか
圧延による製管が行なわれる。その後直接または冷牽加
工等を行った後１０５０℃〜１２００℃に溶体化処理後
使用に供せられる。The steel of the present invention is produced in the same process that normally produces austenitic stainless steel. That is, electric furnaces, converters, and other conventional melting methods can be used, and a billet is produced by casting a steel ingot and going through a blooming process, or by continuous casting, and then pipe-making is performed by hot extrusion or rolling. Thereafter, it is subjected to direct or cold drawing processing and then solution treatment at 1050°C to 1200°C before being used.

【図面の簡単な説明】[Brief explanation of drawings]

第１図は人工灰中の腐食試験によって得られたＳＩ添加
量と腐食減量との関係図、第２図は７００℃ｘｔｏｏｏ
ｈ時効後の靭性とＡＳＩとの関係図であるＯ 浮／　図 第２回 ＳｒFigure 1 is a diagram of the relationship between the amount of SI added and the corrosion weight loss obtained from a corrosion test in artificial ash, and Figure 2 is a diagram of the relationship between the amount of SI added and the corrosion weight loss obtained from a corrosion test in artificial ash.
h A diagram showing the relationship between toughness and ASI after aging.

Claims (1)

【特許請求の範囲】[Claims] （１）Ｃ０，０２〜０，１２チ、Ｓｉ１．７〜３．５チ
。 Ｍｎ　Ｏ，５〜２．５　％　、　Ｃｒ　１５．０〜２６
．−０％、Ｎ１１０．Ｏ〜３０．０％、　ＮＯ，１０〜
０．２５　％を含有し、残部がＦｅ及び不可避的不純物
よりなり、以下の式に示すＡＳＩが−１〜３の範囲にあ
ることを特徴とするがイラチューブ用耐食耐熱用鋼。 ＡＳＩ　＝　（２ＩＣ＋Ｎｉ　＋Ｏ５Ｍｎ　＋１１．５
Ｎ＋　７　）−（３８ｌ−１−Ｏｒ）（２）Ｃ０，０２
〜０．１２チ、Ｓ１１．７〜３．５チ。 Ｍｎ　０．５〜２．５　％　、　Ｃｒ　１５．０〜２６
．０　％　、　Ｎ１１０．０〜３０．０　％　、　ＮＯ
，１０〜０．２５ｔＩｂ１さらにＮｂ　。 Ｔ１の１種又は２種をＮｂ１．０％以下、Ｔ１１．０チ
以下、Ｎｂ＋ＴＩの場合ｉ、ｏ＊以下を含有し、残部が
Ｆｅ及び不可避的不純物よシなシ、以下の式に示すＡＳ
Ｉが−１〜３の範囲にあることを特徴とするメイラチュ
ーブ用耐食耐熱用鋼。 ＡＳＩ　＝　（２１Ｃ＋　Ｎｌ　＋　０．５Ｍｎ　＋　
１１．５Ｎ＋７　）　　（３８ｌ＋Ｃｒ　）（３）Ｃ０
，０２〜０．１　２９６　　、　８１　１．７〜３．５
　チ　。 Ｍｎ　　０．５〜２．５　％　　、　　Ｃｒ　　１５．
０〜２６．０％　　、Ｎｌ　　１０．０〜３０．０係、
ＮＯ，１０〜０．２５チ、さらにＢｏ、０１チ以下を含
有し、残部Ｆｅ及び不可避的不純物よりなり、以下の式
に示すＡＳＩが−１〜３の範囲にあることを特徴とする
がイラチューブ用耐食耐熱用鋼。 ＡＳＩ　＝（２１Ｃ＋Ｎｌ　＋０．５Ｍｎ＋　１１．５
Ｎ＋７　）−（ＢＳＩ　＋Ｃｒ　）（４）　　Ｃ０，０
２〜０．１２係、Ｓ１１．７〜３．５％。 Ｍｎ　０．５−２．５％、　Ｃｒ　１５．Ｑ　〜２６．
０％　、　Ｎｉ　１０．０〜３０．０％、　−Ｎ　Ｏ，
１０〜０．２５俤、さ６にＡｔ０．１チ以下、Ｃａ０．
０５９６以下の１種もしくは２種を含有し、残部がＦｅ
及び不可避的不純物よりなシ、以下の式に示すＡＳＩが
−１〜３の範囲にあることを特徴とするメイラチューブ
用耐食耐熱用鋼。 ＡＳＩ＝（２１Ｃ＋Ｎｌ＋　０．５Ｍｎ＋１１．５Ｎ＋
７　）−（ａＳｌ＋Ｃｒ）（５）Ｃ０，０２〜０．１２
チ、Ｓ１１．７〜３．５％。 Ｍｎ　０．５〜２．５　％　、　　Ｃｒ　　１　５．０
〜２　６．０％　、　　Ｎ１１０．０〜３０．０係、Ｎ
Ｏ，１０〜０．２５係、さらにＮｂ　、　ＴＩの１種又
は２種をＮｂ１．Ｏチリ下、Ｔ１１．０チ以下、Ｎｂ＋
ＴＩの場合１．０％以下とＢｏ、０１係以下を含有し、
残部がＦｅ及び不可避的不純物よりなり、以下の式に示
すＡＳＩが−１ん３の範囲にあることを特徴とするがイ
ラチューブ用耐食耐熱用鋼。 ＡＳＩ　＝（２１Ｃ＋Ｎｉ＋０．５Ｍｎ＋１１．５Ｎ＋
７）　　（３Ｓｌ＋Ｃｒ）（６）Ｃ０，０２〜０．１２
係、Ｓ１１．７〜３．５係。 Ｍｎ　Ｏ，５〜２．５　％　、　Ｃｒ　１５．０〜２６
．０　％　、　Ｎｉ１０．０〜３０．０チ、ＮＯ，１０
〜０．２５係、さらにＮｂ　、　ＴＩの１種又は２種を
Ｎｂ１．０％以下、Ｔ１１．０％以下、Ｎｂ＋Ｔｌの場
合１．（ｌ以下とＡｔ０．１係以下、ＣａＯ，０５％以
下の１種もしくは２柚を含有し、残部がＦｅ及び不可避
的不純物よりなり、以下の式に示すＡＳＩが−１〜３の
範囲にあることを特徴とするボイラチューブ用耐食耐熱
用鋼。 ＡＳＩ　＝（２１Ｃ＋Ｎｉ＋０．５Ｍｎ　＋１１．５Ｎ
＋７）　−（３Ｓｌ＋Ｃｒ）（７）Ｃ０，０２〜０．１
２％、８１１．７〜３．５係。 Ｍｎ　０．５〜２．５　％　　、　　Ｃｒ　　１　５．
０〜２６．０　％　　、　　Ｎｉ１０．０〜３０．０％
　、　ＮＯ，１０−０，２５％　、さらにＢｏ、０１％
以下とＡｔ　Ｏ，１％以下、Ｃａ０．０５％以下の１種
もしくは２種を含有し、残部がＦｅ及び不可避的不純物
よりなり、以下の式に示すＡＳＩが−１〜３の範囲にあ
ることを特徴とするボイラチューブ用耐食耐熱用鋼。 ＡＳＩ＝（２１Ｃ＋Ｎ１＋Ｏ５Ｍｎ＋１１．５Ｎ＋、７
）−（３Ｓｌ＋Ｃｒ）（８）Ｃ０，０２〜０．１２係、
８１１．７〜３．５係。 Ｍｎ　０．５−〜２．５　％　、　Ｃ’ｒ　１５．０〜
２６．０％、　Ｎ１１０．０〜３０．０　％　、　ＮＯ
，１０〜０．２５％、さらにＮｂ　、　ＴＩの１種又は
２種をＮｂ１．０チ以下、Ｔ１１．０チ以下、Ｎｂ　＋
　Ｔｌ　ｔ７）場合１．０係以下とＢ　Ｏ，０１チ以下
さらにＡｔＯ，１チ以下、Ｃａ０．０１％以下の１種も
しくは２種を含有し、残部がＦｅ及び不可避的不純物よ
りなり、以下の式に示すＡＳＩが−１〜３の範囲にある
ことを特徴とするボイラチューブ用耐食耐熱用鋼。 ＡＳＩ＝　（２１Ｃ＋Ｎ１　＋０．５Ｍｎ＋１１．５Ｎ
＋７）−（３ＳＩ＋Ｃｒ）(1) C0.02 to 0.12 inches, Si 1.7 to 3.5 inches. MnO, 5-2.5%, Cr 15.0-26
．． -0%, N110. O ~ 30.0%, NO, 10 ~
0.25%, the remainder being Fe and unavoidable impurities, and having an ASI shown by the following formula in the range of -1 to 3. A corrosion-resistant and heat-resistant steel for flat tubes. ASI = (2IC+Ni +O5Mn +11.5
N+7)-(38l-1-Or)(2)C0,02
~0.12 inch, S11.7~3.5 inch. Mn 0.5-2.5%, Cr 15.0-26
．． 0%, N110.0-30.0%, NO
, 10-0.25tIb1 and further Nb. AS shown in the following formula, containing one or two types of T1, Nb 1.0% or less, T11.0 or less, i, o* or less in the case of Nb + TI, and the balance is Fe and unavoidable impurities.
A corrosion-resistant and heat-resistant steel for mailer tubes, characterized in that I is in the range of -1 to 3. ASI = (21C+Nl+0.5Mn+
11.5N+7) (38l+Cr)(3)C0
,02~0.1 296 ,81 1.7~3.5
blood . Mn 0.5-2.5%, Cr 15.
0 to 26.0%, Nl 10.0 to 30.0,
It is characterized by containing 10 to 0.25 H of NO, and 0.1 H or less of Bo, with the balance consisting of Fe and unavoidable impurities, and having an ASI shown by the following formula in the range of -1 to 3. Corrosion-resistant and heat-resistant steel for tubes. ASI = (21C+Nl +0.5Mn+ 11.5
N+7)-(BSI+Cr)(4) C0,0
2-0.12 ratio, S11.7-3.5%. Mn 0.5-2.5%, Cr 15. Q ~26.
0%, Ni 10.0-30.0%, -NO,
10 to 0.25 t, At 0.1 or less, Ca 0.
Contains one or two of the following: 0596 or less, with the remainder being Fe
A corrosion-resistant and heat-resistant steel for mailer tubes, which is free from inevitable impurities and has an ASI expressed by the following formula in the range of -1 to 3. ASI=(21C+Nl+ 0.5Mn+11.5N+
7)-(aSl+Cr)(5)C0.02~0.12
H, S11.7-3.5%. Mn 0.5-2.5%, Cr15.0
~2 6.0%, N110.0~30.0, N
O, 10 to 0.25, and one or two of Nb and TI to Nb1. O chili below, T11.0 chi or less, Nb+
In the case of TI, it contains 1.0% or less and Bo, 01 or less,
A corrosion-resistant and heat-resistant steel for flat tubes, characterized in that the remainder consists of Fe and unavoidable impurities, and the ASI shown by the following formula is in the range of -1 to 3. ASI = (21C+Ni+0.5Mn+11.5N+
7) (3Sl+Cr)(6)C0.02~0.12
Section S11.7-3.5. MnO, 5-2.5%, Cr 15.0-26
．． 0%, Ni10.0~30.0chi, NO,10
~0.25%, and one or both of Nb and TI, Nb 1.0% or less, T11.0% or less, and in the case of Nb+Tl, 1. (Contains one or two types of citron, At 0.1 or less, CaO, 0.05% or less, and the remainder consists of Fe and unavoidable impurities, and the ASI shown in the following formula is in the range of -1 to 3. Corrosion-resistant and heat-resistant steel for boiler tubes, characterized by: ASI = (21C + Ni + 0.5Mn + 11.5N
+7) −(3Sl+Cr)(7)C0.02~0.1
2%, Section 811.7-3.5. Mn 0.5-2.5%, Cr 1 5.
0~26.0%, Ni10.0~30.0%
, NO, 10-0, 25%, and further Bo, 01%
Contains one or two of the following: At O, 1% or less, Ca 0.05% or less, with the remainder consisting of Fe and unavoidable impurities, and the ASI shown in the formula below is in the range of -1 to 3. Corrosion-resistant and heat-resistant steel for boiler tubes. ASI=(21C+N1+O5Mn+11.5N+, 7
)-(3Sl+Cr)(8)C0.02~0.12,
Section 811.7-3.5. Mn 0.5-2.5%, C'r 15.0-
26.0%, N110.0-30.0%, NO
, 10 to 0.25%, and one or two of Nb and TI, Nb 1.0 or less, T 11.0 or less, Nb +
Tl t7) If it contains 1.0% or less, BO, 0.01% or less, AtO, 1% or less, and Ca0.01% or less, the remainder is Fe and unavoidable impurities, and the following: A corrosion-resistant and heat-resistant steel for boiler tubes, characterized in that the ASI shown by the formula is in the range of -1 to 3. ASI= (21C+N1 +0.5Mn+11.5N
+7)-(3SI+Cr)