JPH0146221B2 - - Google Patents
Info
- Publication number
- JPH0146221B2 JPH0146221B2 JP5802581A JP5802581A JPH0146221B2 JP H0146221 B2 JPH0146221 B2 JP H0146221B2 JP 5802581 A JP5802581 A JP 5802581A JP 5802581 A JP5802581 A JP 5802581A JP H0146221 B2 JPH0146221 B2 JP H0146221B2
- Authority
- JP
- Japan
- Prior art keywords
- heat
- resistant steel
- layer
- casting
- less
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 229910000831 Steel Inorganic materials 0.000 claims description 45
- 239000010959 steel Substances 0.000 claims description 45
- 238000005266 casting Methods 0.000 claims description 20
- 229910017060 Fe Cr Inorganic materials 0.000 claims description 11
- 229910002544 Fe-Cr Inorganic materials 0.000 claims description 11
- UPHIPHFJVNKLMR-UHFFFAOYSA-N chromium iron Chemical compound [Cr].[Fe] UPHIPHFJVNKLMR-UHFFFAOYSA-N 0.000 claims description 11
- 238000002844 melting Methods 0.000 claims description 11
- 230000008018 melting Effects 0.000 claims description 11
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 10
- 238000009750 centrifugal casting Methods 0.000 claims description 10
- 239000012535 impurity Substances 0.000 claims description 7
- 238000000034 method Methods 0.000 claims description 7
- 229930195733 hydrocarbon Natural products 0.000 claims description 6
- 150000002430 hydrocarbons Chemical class 0.000 claims description 6
- 229910052742 iron Inorganic materials 0.000 claims description 5
- 229910052804 chromium Inorganic materials 0.000 claims description 4
- 238000006057 reforming reaction Methods 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 claims description 3
- 229910052748 manganese Inorganic materials 0.000 claims description 2
- 238000004227 thermal cracking Methods 0.000 claims 1
- 239000000463 material Substances 0.000 description 28
- 238000006243 chemical reaction Methods 0.000 description 23
- 239000000956 alloy Substances 0.000 description 21
- 229910045601 alloy Inorganic materials 0.000 description 21
- 230000000694 effects Effects 0.000 description 14
- 239000002184 metal Substances 0.000 description 14
- 229910052751 metal Inorganic materials 0.000 description 14
- 229910052799 carbon Inorganic materials 0.000 description 12
- 239000000203 mixture Substances 0.000 description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 11
- 239000007787 solid Substances 0.000 description 11
- 230000007423 decrease Effects 0.000 description 10
- 238000001556 precipitation Methods 0.000 description 8
- 238000002156 mixing Methods 0.000 description 7
- 239000000126 substance Substances 0.000 description 7
- 230000004907 flux Effects 0.000 description 6
- 230000004927 fusion Effects 0.000 description 6
- 230000007797 corrosion Effects 0.000 description 4
- 238000005260 corrosion Methods 0.000 description 4
- 230000003647 oxidation Effects 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 4
- 238000005979 thermal decomposition reaction Methods 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 230000006866 deterioration Effects 0.000 description 3
- 239000004215 Carbon black (E152) Substances 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 230000008021 deposition Effects 0.000 description 2
- 150000001247 metal acetylides Chemical class 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 238000002303 thermal reforming Methods 0.000 description 2
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000005235 decoking Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 230000003009 desulfurizing effect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000005188 flotation Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 238000010030 laminating Methods 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D19/00—Casting in, on, or around objects which form part of the product
- B22D19/16—Casting in, on, or around objects which form part of the product for making compound objects cast of two or more different metals, e.g. for making rolls for rolling mills
Description
本発明は、炭化水素類の熱分解・改質反応管と
して使用される二重遠心鋳造管の製造方法に関す
る。
炭化水素類の熱分解・改質反応管（クラツキン
グチユーブ等）は高温・高圧、腐食環境下に使用
される。その管材として従来より、HK40材や
HP材等に代表される高Cr高NiのFe−Cr−Ni系
耐熱鋼（Cr：約20〜30％、Ni：約15〜40％）か
らなる鋳造管が賞用されている。
炭化水素類の熱分解・改質反応は、その反応系
から固形炭素が析出する現象を伴うため反応管内
面に固形炭素の付着沈積が生じる。これを放置す
ると、管内の反応流動物の円滑な流通が妨げられ
る等、反応効率の低下をきたす原因となるほか、
浸炭による管材質の劣化、特に延性の著しい低下
を生じ、高圧操業条件下、脆化による管体の割れ
発生の危険が増大する。
この反応管内面の固形炭素の析出沈積は、管材
がNi含有量の高いもの程生じ易く、管材のNi含
有量を制限することにより、その析出沈積を抑制
防止することができる。Fe−Cr−Ni系耐熱鋼鋳
造管（C0.8％、Si1.5％、Mn1.1％、Cr18％、Ni0
〜40％、残部および不純物）を供試反応管とする
反応実験（実験条件：エタン供試量400c.c.／分、
Ｓ／Ｃ比1.5、温度900℃）において、管材Ni量が
15〜35％（HK40材、HP材相当）である場合は
管内面単位面積当り約0.3〜0.5mg／cm2の固形炭素
の析出沈積を避け得ないが、Ni量の減少と共に
その量を減じ、Ni5％以下（０〜５％）の範囲で
は、わずかに0.04〜0.06mg／cm2と、管材Ni量の制
限により固形炭素の析出沈積を効果的に抑制防止
し得ることが本発明者等の実験により確認されて
いる。
従つて反応管として必要な高温・高圧・腐食環
境に耐え得る管材質を保持しつつ固形炭素の管内
面沈積を抑制防止するには、反応管を２層構造と
し、反応系と接触する内層をNi量の制限された
Fe−Cr系耐熱鋼で形成し、外層を従来の管材料
であるHK40材等、高Cr高NiのFe−Cr−Ni系耐
熱鋼で形成するとよい。
遠心鋳造法によれば、回転鋳型内に、外層とな
るFe−Cr−Ni系耐熱鋼溶湯の鋳込みを行つて所
定層厚の外層を形成し、ついで内層となるFe−
Cr系耐熱鋼溶湯を鋳込んで所定層厚の内層を形
成する二重鋳造により目的とする二重構造の反応
管を得ることができる。むろんその二重遠心鋳造
により形成される二層管の外層と内層は、層界面
の全周全長に亘つて確実に融着結合されていなけ
ればならない。このため、従来の二重遠心鋳造で
は、外層を鋳造した後の内層合金溶湯の鋳込み
を、外層が完全に凝固してしまう前に、すなわち
外層の最内面が未凝固の溶融状態を保持している
時点で行うことにより両層の融着結合を確保する
ようにしている。
しかし、その二重遠心鋳造では、両層間の確実
な融合結着を保証し得る反面、外層の合金溶湯と
内層の合金溶湯が過度に混り合うため、内・外両
層の層厚に偏肉を生じると共に、両層の合金の化
学組成の変化をきたし、結果として反応管の二層
構造化による所期の材料特性（固形炭素の析出沈
積抑制防止、高温・高圧特性・腐食抵抗性等）を
十分に発現させることができない。
この両層の合金溶湯の混り合いは、内層合金の
溶融温度（融点）が外層合金のそれより高い程顕
著となる。その合金溶湯の混り合いを抑制しよう
として内層合金溶湯の鋳込み温度（鋳込み温度
は、合金溶湯の品質維持と湯流れ性確保等の面か
ら、一般に融点より約150〜250℃高い温度とされ
る）を低くすると、内層の品質の低下・注湯経路
の閉塞のおそれがあるだけでなく、層界面の金属
学的結合も不完全なものとなる。また鋳造合金溶
湯の酸化防止や溶湯中の非金属介在物の吸着除去
等の目的でフラツクスを鋳型内溶湯面に散布投与
する場合は、フラツクスの完全な浮上分離が妨げ
られて金属中に混在し、管在の重大な欠陥となる
等の不都合をきたす。
本発明は二重遠心鋳造による反応管の製造に関
する上記問題を解決するためになされたものであ
る。
本発明は、高Cr高NiのFe−Cr−Ni系耐熱鋼か
らなる外層と、Fe−Cr系耐熱鋼からなる内層と
の２層構造を有する炭化水素類熱分解・改質反応
管の二重遠心鋳造において、
C0.2〜0.6％（重量％、以下同じ）、Si2.5％以
下、Mn2.5％以下、Cr20〜30％、Ni15〜40％、
残部鉄および不純物であるFe−Cr−Ni系耐熱鋼
からなる外層を鋳造し、その最内面まで凝固した
のち、C1.5〜3.5％、Si2.5％以下、Mn2.5％以下、
Cr12〜30％、残部鉄および不純物であつて、前
記外層耐熱鋼より低い融点を有するFe−Cr系耐
熱鋼からなる内層の鋳造を行うことを特徴として
いる。
本発明は、Fe−Cr−Ni系耐熱鋼の外層を鋳造
した後の内層形成用Fe−Cr系耐熱鋼溶湯の鋳込
みを、外層が最内面まで凝固した後に行うことと
しているので、外層最内面が溶融状態にある時点
で内層合金溶湯の鋳込みを行う従来の鋳造法にお
けるような内・外両層合金の過度の混り合いとそ
れによる各層の層厚のバラツキ（偏肉）や合金化
学組成の変化を生じることがない。また外層耐熱
鋼（Ｃ：0.2〜0.6％）に対し、内層耐熱鋼のＣ含
有量を1.5〜3.5％と、耐熱鋼としての仕様を損な
わない範囲内で高目に設定して外層耐熱鋼より低
い融点をもたせているので、外層の最内面凝固後
に内層の鋳造を行うこととしているに拘らず、外
層と内層との界面の良好な金属学的結合関係を形
成することができる。すなわち、本発明の二重遠
心鋳造によれば、内・外両層合金溶湯の過度の混
り合いとそれに伴う両層の偏肉・境界の乱れがな
く、両層とも所定の化学組成と所定の層厚を有
し、かつ層界面に形成された必要最小限の薄い融
合層による両層の金属学的結合関係を備えた二層
管を得ることができる。
本発明における二重遠心鋳造には特別の条件の
付加・制限を必要とせず、Fe−Cr−Ni系耐熱鋼
からなる外層およびFe−Cr系耐熱鋼からなる内
層のそれぞれの鋳造は、常法に従つてその合金の
適正鋳込み温度で行えばよく、また合金溶湯の酸
化防止・清浄度の改善等を目的としてフラツクス
を使用する場合の鋳型内溶湯への添加投与も常法
に従つて行えばよい。
本発明により製造される二層管は、高Cr高Ni
のFe−Cr−Ni系耐熱鋼からなる外層により反応
管として必要な高温材料特性を確保しつつ、内層
をNi量の制限されたFe−Cr系耐熱鋼で形成する
ことにより、管内反応系からの固形炭素の析出反
応を抑制するようにしている。その外層および内
層を形成する各耐熱鋼の化学組成限定理由を説明
すれば次のとおりである。なお、両層界面の金属
学的結合を形成するための外層耐熱鋼と内層耐熱
鋼との間の融点の相対的高低の調整は、それぞれ
について規定された化学組成の範囲内において主
としてＣ含有量の調節により行えばよい。
まず外層を形成するFe−Cr−Ni系耐熱鋼の成
分限定理由について説明する。この耐熱鋼の成分
構成は従来の代表的管材であるHK40材やHP材
に相当するものである。
Ｃ：0.2〜0.6％
Ｃは管材の高温強度を高める効果を有する。
0.2％を下限とするのは、それ未満では高温クリ
ープラプチヤー強度を十分なものとすることがで
きないからであり、0.6％を上限とするのは、そ
れを越えると、延靭性の低下、配管施工に必要な
溶接性の悪化等を招くからである。
Si：2.5％以下
Siは脱酸剤であり、また溶湯の流動性を高め鋳
造性を良好なものとするために添加されるが、
2.5％を越えると、管材の延靭性の低下、鋳造割
れ、溶接性低下等をきたすので、2.5％を上限と
する。
Mn：2.5％以下
Mnは脱硫・脱酸元素であり、また溶湯の流動
性を高め、良好な鋳造性をもたらす元素である。
しかし、2.5％を越えると、高温クリープ強度等、
高温強度の低下を招くので、2.5％以下とする。
Cr：20〜30％
Crは反応管用耐熱鋼として必要な高温強度お
よび高温耐酸化性を確保するために、少なくとも
20％を必要とする。しかし、30％を越えると、延
靭性の低下、溶接性の悪化等をきたす。このた
め、20〜30％とする。
Ni：15％〜40％
Niは前記Crと共に、反応管材として必要な高
温強度、耐酸化性等の確保に不可欠の元素であ
る。15％を下限とするのは、その改善効果を十分
ならしめるためであり、その添加増量に伴つて効
果を増す。反応操業条件が高温化する程、Ni含
有量を高めるのが好ましい。しかし40％を越える
と、効果の増加は少なくなり経済的に不利とな
る。このため、15〜40％とする。
次に内層材であるFe−Cr系耐熱鋼の成分限定
理由を述べる。
Ｃ：1.5〜3.5％
内層耐熱鋼のＣ量を1.5％以上と、外層のFe−
Cr−Ni系耐熱鋼のそれ（Ｃ：0.2〜0.6％）に比べ
て高Ｃ組成としたのは、外層耐熱鋼より低い融点
をもたせるためである。Ｃ量の増加と共に、融点
の降下をみるが、あまり多くすると、Cr炭化物
の生成によるCr消耗量の増加と耐食性の低下を
きたし、また多量の炭化物の生成に伴い管材の脆
化、鋳造割れ等を生じるので、3.5％を上限とす
る。
Si：2.5％以下
Siは脱酸、および溶湯の流動性向上のために添
加される。また、管材の耐浸炭性の改善効果を有
する。しかし、2.5％を越えて添加すると、管材
の延性の低下、鋳造割れ、溶接性悪化等をきたす
ので2.5％以下とする。
Mn：2.5％以下
Mnは脱硫・脱酸作用、溶湯の流動性向上効果
を有し、またその添加増量により、浸炭抑制作用
を発現する。しかし、多量の添加は、σ相の生成
とそれによる管材の脆化をきたすので、2.5％を
上限とする。
Cr：12〜30％
Crは高温耐酸化性、耐食性、および耐浸炭性
等の改善効果を有する。12％未満ではその効果が
不足する。添加増量に伴つて効果の増加をみる
が、30％を越えると、高温使用に伴う管材の延性
低下が大きくなる。このため、12〜30％とする。
上記各耐熱鋼はいづれも、通常の合金溶製技術
上不可避の不純物の混入が許容される。例えばＰ
は0.04％以下、Ｓは0.04％以下混在して何らさし
つかえない。また、反応系と接触する管内面の固
形炭素の析出沈積抑制効果は、前記のようにNi
量５％以下の範囲であれば十分に確保されるの
で、内層を形成するFe−Cr系耐熱鋼は、５％以
下の範囲内で不純物としてのNiの混在が許容さ
れる。
なお、上記外層および内層を形成する各耐熱鋼
は、材質の改善を目的として鉄の一部が、３％以
下のNb、８％以下のＷ、５％のMo、0.3％以下
のＮから選ばれる１種ないし２種以上の元素で置
換された化学組成としてもよい。
実施例
横型遠心鋳造により、HK40相当のFe−Cr−
Ni系耐熱鋼からなる外層を鋳造し、その最内面
まで凝固したのち、高ＣのFe−Cr系耐熱鋼溶湯
を鋳込んで内層を形成することにより、外径135
mm、肉厚23mm（外層厚：15mm、内層厚：８mm）の
二層管を得た。なお、外層鋳造時にフラツクス
（SiO2：50％、Na2B4O7：30％、Na2CO3：20％）
を通常の使用法に従つて鋳型内溶湯面に散布投与
した。
比較例として、上記と同じFe−Cr−Ni系耐熱
鋼からなる外層の鋳造後、低ＣのFe−Cr系耐熱
鋼溶湯を鋳込んで内層を形成することにより、上
記と同じ管サイズの二層管を得た。その外層鋳造
の際には上記と同じフラツクスを同じ要領で溶湯
面に散布投与した。但し、内層溶湯の鋳込みは、
外層との過度の混り合いを抑制する目的でやや低
めの温度で行つた。
第１表に内・外層の耐熱鋼の化学成分組成、融
点、および鋳込み温度を示す。
The present invention relates to a method for manufacturing a double centrifugal cast tube used as a reaction tube for thermal decomposition and reforming of hydrocarbons. Hydrocarbon thermal decomposition/reforming reaction tubes (cracking tubes, etc.) are used in high temperature, high pressure, and corrosive environments. Traditionally, HK40 material and
Cast pipes made of high-Cr, high-Ni heat-resistant steel (Cr: about 20-30%, Ni: about 15-40%), such as HP material, are widely used. The thermal decomposition/reforming reaction of hydrocarbons is accompanied by a phenomenon in which solid carbon is precipitated from the reaction system, resulting in deposition of solid carbon on the inner surface of the reaction tube. If this is left unattended, it may impede the smooth flow of the reaction fluid in the tube, resulting in a decrease in reaction efficiency.
Carburization causes deterioration of the pipe material, particularly a significant decrease in ductility, and increases the risk of cracking of the pipe due to embrittlement under high-pressure operating conditions. This precipitation of solid carbon on the inner surface of the reaction tube is more likely to occur when the tube material has a higher Ni content, and by limiting the Ni content of the tube material, this precipitation and precipitation can be suppressed and prevented. Fe-Cr-Ni heat-resistant steel cast pipe (C0.8%, Si1.5%, Mn1.1%, Cr18%, Ni0
-40%, remainder and impurities) as the test reaction tube (experimental conditions: ethane sample amount 400 c.c./min,
At an S/C ratio of 1.5 and a temperature of 900°C, the amount of Ni in the pipe material was
15 to 35% (equivalent to HK40 material and HP material), it is unavoidable to precipitate and deposit about 0.3 to 0.5 mg/ cm2 of solid carbon per unit area of the inner surface of the tube, but this amount can be reduced as the amount of Ni decreases. In the range of Ni 5% or less (0 to 5%), the present inventors have found that the precipitation of solid carbon can be effectively suppressed and prevented by limiting the amount of Ni in the pipe material, which is only 0.04 to 0.06 mg/cm2. This has been confirmed through experiments. Therefore, in order to suppress and prevent the deposition of solid carbon on the inner surface of the tube while maintaining a tube material that can withstand the high temperatures, high pressures, and corrosive environments necessary for reaction tubes, the reaction tube should be constructed with two layers, and the inner layer in contact with the reaction system should be Limited amount of Ni
It is preferable that the tube is made of Fe-Cr heat-resistant steel, and the outer layer is made of high-Cr, high-Ni Fe-Cr-Ni heat-resistant steel such as HK40 material, which is a conventional pipe material. According to the centrifugal casting method, molten Fe-Cr-Ni heat-resistant steel is poured into a rotary mold to form an outer layer with a predetermined thickness, and then Fe-Cr-Ni heat-resistant steel is poured into a rotary mold to form an inner layer.
The desired double-structured reaction tube can be obtained by double casting, in which molten Cr-based heat-resistant steel is cast to form an inner layer of a predetermined thickness. Of course, the outer layer and inner layer of the two-layer tube formed by double centrifugal casting must be reliably fused and bonded over the entire circumference of the layer interface. For this reason, in conventional double centrifugal casting, the inner layer molten alloy is poured after the outer layer is cast before the outer layer is completely solidified, that is, the innermost surface of the outer layer is kept in an unsolidified molten state. By doing this at a certain point, the fusion bond between both layers is ensured. However, although double centrifugal casting can guarantee reliable fusion and bonding between both layers, the molten alloy in the outer layer and the molten alloy in the inner layer mix excessively, resulting in uneven layer thickness for both the inner and outer layers. At the same time, the chemical composition of the alloy in both layers changes, and as a result, the two-layer structure of the reaction tube achieves the desired material properties (prevention of solid carbon precipitation, high temperature/high pressure properties, corrosion resistance, etc.) ) cannot be fully expressed. This mixing of the molten alloys in both layers becomes more pronounced as the melting temperature (melting point) of the inner layer alloy is higher than that of the outer layer alloy. In an attempt to suppress mixing of the molten alloy, the temperature at which the inner layer molten alloy is poured (the casting temperature is generally set at a temperature approximately 150 to 250°C higher than the melting point in order to maintain the quality of the molten alloy and ensure flowability) ) is not only likely to deteriorate the quality of the inner layer and block the pouring path, but also to make the metallurgical bond at the layer interface incomplete. In addition, when flux is sprayed onto the surface of the molten metal in the mold for the purpose of preventing oxidation of the molten casting alloy or adsorbing and removing non-metallic inclusions in the molten metal, complete flotation and separation of the flux is prevented and the flux is mixed in the metal. , causing inconveniences such as serious defects in management. The present invention has been made in order to solve the above-mentioned problems regarding the manufacture of reaction tubes by double centrifugal casting. The present invention provides a hydrocarbon pyrolysis/reforming reaction tube having a two-layer structure: an outer layer made of high Cr, high Ni Fe-Cr-Ni heat-resistant steel, and an inner layer made of Fe-Cr heat-resistant steel. In heavy centrifugal casting, C0.2-0.6% (weight%, same below), Si2.5% or less, Mn2.5% or less, Cr20-30%, Ni15-40%,
After casting the outer layer consisting of Fe-Cr-Ni heat-resistant steel with the balance iron and impurities and solidifying it to its innermost surface, it is cast with C1.5 to 3.5%, Si 2.5% or less, Mn 2.5% or less,
The method is characterized in that the inner layer is made of Fe--Cr heat-resistant steel, which contains 12 to 30% Cr, the balance being iron and impurities, and has a lower melting point than the outer heat-resistant steel. In the present invention, after the outer layer of the Fe-Cr-Ni heat-resistant steel is cast, the Fe-Cr heat-resistant steel molten metal for forming the inner layer is poured after the outer layer has solidified to the innermost surface. Excessive mixing of both the inner and outer alloy layers, resulting in variations in the thickness of each layer (uneven thickness) and alloy chemical composition, as in conventional casting methods in which the molten inner layer alloy is poured when the inner layer is in a molten state. No change occurs. In addition, the C content of the inner layer heat-resistant steel is set to 1.5-3.5% compared to the outer layer heat-resistant steel (C: 0.2-0.6%), which is higher than the outer layer heat-resistant steel within the range that does not impair the specifications as a heat-resistant steel. Since it has a low melting point, a good metallurgical bonding relationship can be formed at the interface between the outer layer and the inner layer, even though the inner layer is cast after the outermost layer is solidified. In other words, according to the double centrifugal casting of the present invention, there is no excessive mixing of the molten alloy in both the inner and outer layers, and there is no accompanying uneven thickness or disturbance of the boundary between the two layers, and both layers have a predetermined chemical composition and a predetermined thickness. It is possible to obtain a two-layer tube having a layer thickness of , and having a metallurgical bonding relationship between both layers by a minimum necessary thin fusion layer formed at the layer interface. The double centrifugal casting in the present invention does not require the addition or restriction of special conditions, and the casting of the outer layer made of Fe-Cr-Ni heat-resistant steel and the inner layer made of Fe-Cr heat-resistant steel can be carried out using conventional methods. Therefore, it is sufficient to perform the casting at the appropriate casting temperature for the alloy, and when flux is used for the purpose of preventing oxidation and improving the cleanliness of the molten alloy, it is necessary to add it to the molten metal in the mold according to the conventional method. good. The double-layer pipe manufactured by the present invention has high Cr, high Ni
The outer layer made of Fe-Cr-Ni heat-resistant steel ensures the high-temperature material properties necessary for the reaction tube, while the inner layer is made of Fe-Cr heat-resistant steel with a limited Ni content, allowing the reaction system to be removed from the inside of the tube. This is to suppress the precipitation reaction of solid carbon. The reasons for limiting the chemical composition of each heat-resistant steel forming the outer layer and inner layer are as follows. In addition, adjustment of the relative height of the melting point between the outer layer heat-resistant steel and the inner layer heat-resistant steel in order to form a metallurgical bond at the interface of both layers is mainly done by adjusting the C content within the range of the chemical composition specified for each. This can be done by adjusting. First, the reason for limiting the composition of the Fe-Cr-Ni heat-resistant steel that forms the outer layer will be explained. The composition of this heat-resistant steel corresponds to HK40 material and HP material, which are conventional typical pipe materials. C: 0.2 to 0.6% C has the effect of increasing the high temperature strength of the pipe material.
The reason why the lower limit is set at 0.2% is that if it is less than that, the high-temperature creep rapture strength will not be sufficient, and the reason why the upper limit is set at 0.6% is that if it exceeds it, the ductility will deteriorate and the piping will be damaged. This is because it causes deterioration of weldability required for construction. Si: 2.5% or less Si is a deoxidizing agent and is added to improve the fluidity of the molten metal and improve castability.
If it exceeds 2.5%, it will cause a decrease in the ductility of the pipe material, casting cracks, and a decrease in weldability, so the upper limit is set at 2.5%. Mn: 2.5% or less Mn is a desulfurizing and deoxidizing element, and is also an element that increases the fluidity of molten metal and provides good castability.
However, if it exceeds 2.5%, high temperature creep strength etc.
Since it causes a decrease in high-temperature strength, it should be kept at 2.5% or less. Cr: 20-30% Cr is at least
Requires 20%. However, when it exceeds 30%, ductility and weldability deteriorate, etc. For this reason, it is set at 20 to 30%. Ni: 15% to 40% Ni, together with the above-mentioned Cr, is an essential element for ensuring high temperature strength, oxidation resistance, etc. necessary for a reaction tube material. The reason for setting the lower limit at 15% is to ensure that the improvement effect is sufficient, and the effect increases as the amount added is increased. It is preferable to increase the Ni content as the reaction operating conditions become higher in temperature. However, if it exceeds 40%, the increase in effectiveness will be small and it will be economically disadvantageous. Therefore, it is set at 15-40%. Next, we will discuss the reasons for limiting the composition of the Fe-Cr heat-resistant steel, which is the inner layer material. C: 1.5 to 3.5% The amount of C in the inner layer heat-resistant steel is 1.5% or more, and the Fe-
The reason for having a higher C composition than that of Cr-Ni heat-resistant steel (C: 0.2 to 0.6%) is to have a melting point lower than that of the outer layer heat-resistant steel. As the amount of C increases, the melting point decreases, but if the amount is too high, Cr consumption increases and corrosion resistance decreases due to the formation of Cr carbides, and the formation of a large amount of carbides causes embrittlement of the pipe material, casting cracks, etc. Therefore, the upper limit is set at 3.5%. Si: 2.5% or less Si is added to deoxidize and improve the fluidity of the molten metal. It also has the effect of improving carburization resistance of pipe materials. However, if added in excess of 2.5%, the ductility of the pipe material will decrease, casting cracks, weldability will deteriorate, etc., so the content should be 2.5% or less. Mn: 2.5% or less Mn has a desulfurization/deoxidizing effect and an effect of improving the fluidity of molten metal, and by increasing its addition, it exhibits a carburization suppressing effect. However, adding a large amount causes the formation of σ phase and the resulting embrittlement of the pipe material, so the upper limit is set at 2.5%. Cr: 12-30% Cr has the effect of improving high temperature oxidation resistance, corrosion resistance, carburization resistance, etc. If it is less than 12%, the effect will be insufficient. The effect increases as the amount added increases, but if it exceeds 30%, the ductility of the pipe material decreases significantly due to high temperature use. Therefore, it is set at 12 to 30%. All of the heat-resistant steels mentioned above are allowed to contain impurities that are unavoidable due to normal alloy melting technology. For example, P
0.04% or less and S 0.04% or less are acceptable. In addition, as mentioned above, the effect of suppressing the precipitation of solid carbon on the inner surface of the tube that comes into contact with the reaction system is
As long as the content is within the range of 5% or less, it is sufficiently ensured, so that the Fe-Cr heat-resistant steel forming the inner layer is allowed to contain Ni as an impurity within the range of 5% or less. In order to improve the material quality of each of the heat-resistant steels forming the outer and inner layers, a portion of the iron is selected from 3% or less Nb, 8% or less W, 5% Mo, and 0.3% or less N. It is also possible to have a chemical composition substituted with one or more kinds of elements. Example Fe-Cr- equivalent to HK40 was produced by horizontal centrifugal casting.
After casting the outer layer made of Ni-based heat-resistant steel and solidifying it to its innermost surface, the inner layer is formed by casting high C Fe-Cr-based heat-resistant steel molten metal.
A two-layer tube with a wall thickness of 23 mm (outer layer thickness: 15 mm, inner layer thickness: 8 mm) was obtained. In addition, flux (SiO 2 : 50%, Na 2 B 4 O 7 : 30%, Na 2 CO 3 : 20%) is added during outer layer casting.
was sprayed onto the surface of the molten metal in the mold according to the usual usage method. As a comparative example, after casting the outer layer made of the same Fe-Cr-Ni heat-resistant steel as above, a low C molten Fe-Cr heat-resistant steel was cast to form the inner layer. A layer tube was obtained. When casting the outer layer, the same flux as above was sprayed onto the molten metal surface in the same manner. However, when casting the inner layer molten metal,
The temperature was slightly lower in order to prevent excessive mixing with the outer layer. Table 1 shows the chemical composition, melting point, and casting temperature of the heat-resistant steel of the inner and outer layers.
【表】
前記２つの二層管のそれぞれの径方向断面図を
第１図（発明例）および第２図（比較例）に示
す。両図から明らかなように、比較例の二層管
は、層界面の融着が不完全であるのに対し、発明
例のそれは、外層と内層とが全周に亘つて薄い融
合層を介して金属学的に密着結合し、その層境界
は比較的明瞭であり、両合金の過度の混り合いや
偏肉等のない健全な層構造を有している。
以上のように、本発明方法により製造される
Fe−Cr−Ni系耐熱鋼の外層とFe−Cr系耐熱鋼の
内層とからなる二層管は健全な積層構造を有し、
両層合金の過度の混り合いがなく、必要最小限の
融合層を介して両層の強固な密着結合関係が形成
されている。従つて炭化水素類の熱分解・改質反
応管としての使用においては、異種耐熱鋼の積層
複合効果として、反応管に必要な高温強度・耐熱
性・耐食性等が保証されると共に、管内面に対す
る反応系からの固形炭素析出沈積の改善効果によ
り、反応効率の向上・安定化、管材劣化防止等と
ともに、沈積固形炭素除去のための操業中断や除
去作業（所謂デコーキング）等の頻度が減少し操
業効率の改善・安全性向上等の効果が得られる。[Table] The respective radial cross-sectional views of the two double-layered pipes are shown in FIG. 1 (inventive example) and FIG. 2 (comparative example). As is clear from both figures, in the two-layer pipe of the comparative example, the fusion at the layer interface is incomplete, whereas in the inventive example, the outer layer and the inner layer are bonded over the entire circumference through a thin fusion layer. The two alloys are closely bonded metallurgically, the layer boundaries are relatively clear, and the two alloys have a sound layer structure without excessive mixing or uneven thickness. As described above, produced by the method of the present invention
The double-layer pipe consists of an outer layer of Fe-Cr-Ni heat-resistant steel and an inner layer of Fe-Cr heat-resistant steel, and has a sound laminated structure.
There is no excessive mixing of the alloys in both layers, and a strong close bonding relationship between the two layers is formed through the necessary minimum number of fusion layers. Therefore, when used as a reaction tube for thermal decomposition and reforming of hydrocarbons, the composite effect of laminating different types of heat-resistant steel ensures the high-temperature strength, heat resistance, corrosion resistance, etc. required for the reaction tube, and also provides protection against the inner surface of the tube. The effect of improving solid carbon precipitation from the reaction system improves and stabilizes reaction efficiency, prevents deterioration of pipe materials, and reduces the frequency of operational interruptions and removal work (so-called decoking) to remove deposited solid carbon. Effects such as improved operational efficiency and safety can be obtained.
第１図および第２図は二重遠心鋳造管の径方向
断面における金属組織を示す図面代用写真であ
る。
FIGS. 1 and 2 are photographs substituted for drawings showing the metal structure in a radial cross section of a double centrifugally cast tube.
Claims (1)
下、Mn2.5％以下、Cr20〜30％、Ni15〜40％、
残部鉄および不純物であるFe−Cr−Ni系耐熱鋼
からなる外層を鋳造し、その最内面まで凝固した
のち、C1.5〜3.5％、Si2.5％以下、Mn2.5％以下、
Cr12〜30％、残部鉄および不純物であつて、前
記外層耐熱鋼より低い融点を有するFe−Cr系耐
熱鋼からなる内層の鋳造を行うことを特徴とする
炭化水素類の熱分解・改質反応管用二重遠心鋳造
管の製造方法。1 C0.2-0.6% (weight%, same below), Si2.5% or less, Mn2.5% or less, Cr20-30%, Ni15-40%,
After casting the outer layer consisting of Fe-Cr-Ni heat-resistant steel with the balance iron and impurities and solidifying it to its innermost surface, it is cast with C1.5 to 3.5%, Si 2.5% or less, Mn 2.5% or less,
Thermal cracking and reforming reaction of hydrocarbons, characterized by casting an inner layer made of Fe-Cr heat-resistant steel containing 12 to 30% Cr, the balance iron and impurities, and having a lower melting point than the outer heat-resistant steel. A method for manufacturing double centrifugal casting tubes for pipes.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5802581A JPS57175066A (en) | 1981-04-17 | 1981-04-17 | Production of double pipe by centrifugal casting |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5802581A JPS57175066A (en) | 1981-04-17 | 1981-04-17 | Production of double pipe by centrifugal casting |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS57175066A JPS57175066A (en) | 1982-10-27 |
| JPH0146221B2 true JPH0146221B2 (en) | 1989-10-06 |
Family
ID=13072402
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP5802581A Granted JPS57175066A (en) | 1981-04-17 | 1981-04-17 | Production of double pipe by centrifugal casting |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS57175066A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103032637A (en) * | 2013-01-07 | 2013-04-10 | 北京东鑫顺通耐磨技术有限公司 | Bimetal composite pipe and production method thereof |
| CN103042071B (en) * | 2013-01-07 | 2015-09-30 | 北京东鑫顺通耐磨技术有限公司 | A kind of Double-metal composite elbow and production method thereof |
| CN110117751B (en) * | 2019-06-18 | 2020-10-27 | 山东远大锅炉配件制造有限公司 | Wear-resistant corrosion-resistant bimetal composite pipe material and preparation method thereof |
-
1981
- 1981-04-17 JP JP5802581A patent/JPS57175066A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS57175066A (en) | 1982-10-27 |
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