JPH01191740A - Production of seamless extend-forged steel pipe having excellent carburization resistance - Google Patents
Production of seamless extend-forged steel pipe having excellent carburization resistanceInfo
- Publication number
- JPH01191740A JPH01191740A JP1509988A JP1509988A JPH01191740A JP H01191740 A JPH01191740 A JP H01191740A JP 1509988 A JP1509988 A JP 1509988A JP 1509988 A JP1509988 A JP 1509988A JP H01191740 A JPH01191740 A JP H01191740A
- Authority
- JP
- Japan
- Prior art keywords
- steel pipe
- seamless
- heat treatment
- extend
- oxide scale
- 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.)
- Pending
Links
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 34
- 239000010959 steel Substances 0.000 title claims abstract description 34
- 238000004519 manufacturing process Methods 0.000 title claims description 11
- 238000010438 heat treatment Methods 0.000 claims abstract description 22
- 239000000463 material Substances 0.000 claims abstract description 13
- 239000002344 surface layer Substances 0.000 claims abstract description 12
- 238000007796 conventional method Methods 0.000 claims abstract description 6
- 230000001590 oxidative effect Effects 0.000 claims description 7
- 239000002994 raw material Substances 0.000 claims description 6
- 239000010410 layer Substances 0.000 abstract description 14
- 239000013078 crystal Substances 0.000 abstract description 4
- 239000000126 substance Substances 0.000 abstract description 4
- 238000009792 diffusion process Methods 0.000 abstract description 3
- 230000007935 neutral effect Effects 0.000 abstract description 2
- 230000015572 biosynthetic process Effects 0.000 abstract 1
- 239000008246 gaseous mixture Substances 0.000 abstract 1
- 238000000465 moulding Methods 0.000 abstract 1
- 238000000034 method Methods 0.000 description 10
- 239000007789 gas Substances 0.000 description 6
- 238000005255 carburizing Methods 0.000 description 5
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 3
- 239000005977 Ethylene Substances 0.000 description 3
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 3
- 238000001192 hot extrusion Methods 0.000 description 3
- 239000001257 hydrogen Substances 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- 238000013508 migration Methods 0.000 description 3
- 230000005012 migration Effects 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 239000003208 petroleum Substances 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000002791 soaking Methods 0.000 description 2
- 238000005979 thermal decomposition reaction Methods 0.000 description 2
- 235000008331 Pinus X rigitaeda Nutrition 0.000 description 1
- 235000011613 Pinus brutia Nutrition 0.000 description 1
- 241000018646 Pinus brutia Species 0.000 description 1
- 229910001069 Ti alloy Inorganic materials 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 125000004429 atom Chemical group 0.000 description 1
- 239000010953 base metal Substances 0.000 description 1
- 238000005422 blasting Methods 0.000 description 1
- 239000003610 charcoal Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000010622 cold drawing Methods 0.000 description 1
- 238000005097 cold rolling Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- -1 ethylene, propylene Chemical group 0.000 description 1
- 239000000295 fuel oil Substances 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- JVJQPDTXIALXOG-UHFFFAOYSA-N nitryl fluoride Chemical compound [O-][N+](F)=O JVJQPDTXIALXOG-UHFFFAOYSA-N 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 150000002926 oxygen Chemical class 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 238000005554 pickling Methods 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 230000003746 surface roughness Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000004227 thermal cracking Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Abstract
Description
【発明の詳細な説明】
〔産業上の利用分野〕
本発明は、浸炭性雰囲気下で使用される２５Ｃｒ−３２
Ｎｉ系耐熱鋼製の継目無鍛伸鋼管の製造方法に関する。DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to 25Cr-32 used in a carburizing atmosphere.
The present invention relates to a method of manufacturing a seamless unforged steel pipe made of Ni-based heat-resistant steel.
ナフサ等の石油系原料からエチレン、プロピレン等を製
造する化学工業用装置として、エチレン分解炉があり、
この分解炉内には内部に一定速度で流通せしめられる石
油系原料を外部から重油バーす等を用いて加熱すること
によって熱分解させる加熱分解管が設けられている。Ethylene cracking furnaces are used in the chemical industry to produce ethylene, propylene, etc. from petroleum-based raw materials such as naphtha.
This cracking furnace is provided with a thermal cracking tube that thermally decomposes the petroleum-based raw material, which is allowed to flow inside at a constant rate, by heating it from the outside using a heavy oil bar or the like.
この加熱分解管としては、ＡＳＴＭ−ＨＫ４０（２５Ｃ
ｒ−２ＯＮｉ−α４Ｃ鋼）で代表される遠心鋳造管や通
称名Ａ１１ｏｙ ８００ （２０Ｃｒ −３２Ｎｉ−Ａ
ｌｌ、Ｔｉ合金）製の鍛伸管がある。This thermal decomposition tube is ASTM-HK40 (25C
r-2ONi-α4C steel), commonly known as A11oy 800 (20Cr-32Ni-A
There are forged and drawn pipes made of Ti alloys.
しかし、前者は遠心鋳造管であるため小径薄肉管及び長
尺管の製造が実質上不可能で、強度上不安定な溶接部が
増加する等の鋳造管特仔の欠点があった。また、後者は
鍛伸管であるため小径薄肉管及び長尺管の製造が可能で
あるものの前者に比べて高温強度が劣るという欠点があ
った。However, since the former is a centrifugally cast pipe, it is virtually impossible to manufacture small-diameter, thin-walled pipes and long pipes, and there are drawbacks to cast pipes, such as an increase in the number of welded parts that are unstable in terms of strength. Furthermore, since the latter is a forged and drawn pipe, it is possible to manufacture small-diameter, thin-walled pipes and long pipes, but it has the drawback of being inferior in high-temperature strength compared to the former.
このため、本出願人は、先に、十分な高温強度を備える
一方、加工性、溶接性等にも優れる鍛伸管製造用として
適宜な量のＴ ｓ １Ａ１．、ＩＩ％Ｍ ｇ ｓＭ Ｏ
％ Ｗ ｓ Ｃｏ ｓ Ｚ ｒを含をせしめた２５Ｃｒ
−３２Ｎｉ系の耐熱鋼を、特公昭５１−２９９６２号公
報及び特開昭５７−２３０５０号公報で提案している。For this reason, the present applicant first developed an appropriate amount of T s 1A1. , II%M g sM O
% W s Co s Z 25Cr containing r
-32Ni-based heat-resistant steel has been proposed in Japanese Patent Publication No. 51-29962 and Japanese Patent Application Laid-open No. 57-23050.
しかしながら、本出願人が先に提案した前記各公報に開
示される２５Ｃｒ−３２Ｎｉ系の耐熱鋼を素材とし、常
法（所謂マンネスマン製管法、熱間押出し製管法又は熱
間押抜き製管法或いは前記各製管法で得られた管に冷間
引抜き又は冷間圧延加工を施す方法）によって所定形杖
・寸法の継目無管に成形し、この成形継目無管に大気雰
囲気中で最終の熱処理を施し、次いで脱スケール処理し
て製造していた継目無鍛伸鋼管を前述の高温環境下で用
いた場合には、前記ＨＫ４０！！！の鋳造管に比べて管
内外表面、特に管内表面側への浸炭が多いという欠点の
あることが判明し、この改善が強く望まれている。However, using the 25Cr-32Ni heat-resistant steel disclosed in the above-mentioned publications as previously proposed by the present applicant, conventional methods (so-called Mannesmann tube manufacturing method, hot extrusion tube manufacturing method, or hot extrusion tube manufacturing method) are used. A method of cold drawing or cold rolling the pipe obtained by each of the above-mentioned pipe manufacturing methods) is used to form a seamless pipe of a predetermined shape and size, and this formed seamless pipe is subjected to a final process in an atmospheric atmosphere. When a seamless drawn steel pipe that had been heat-treated and then descaled was used in the above-mentioned high-temperature environment, the above-mentioned HK40! ! ! It has been found that this method has a disadvantage in that there is more carburization on the inner and outer surfaces of the tube, especially on the inner surface side, compared to cast tubes, and there is a strong desire to improve this problem.
そこで、本発明者等は、エチレン分解炉の如き浸炭性雰
囲気下での前述した工程を経て製造した前記本出願人の
先の出願に係わる２５Ｃｒ−３２Ｎｉ系耐熱ｆ１４製の
継目無鍛伸管にみられる前記“浸炭”の発生防止手段を
見い出すべく、調査研究を行なったところ、
■ 管内面側に生成付着した酸化スケール層は、Ｃｒ
ｓ Ｆ ｃ １Ｍ ｎからなるスピネル型の酸化物が主
体であること、
■ 浸炭は、前記酸化スケール層が生成付着した管内表
面に多いこと、
■ 両足酸化スケール層が生成付着した部分の管内表面
層部分のＣｒｂ：４度は、母材部分のＣｒ濃度に比べて
低いこと、
■ 前記■〜■の現象は、Ｉ−ＩＫ４０製の鋳造管には
ほとんど認められないこと、
なる事実が判明した。この事実に基づいて■ 前記“浸
炭”は、高温（１０５０℃程度）に加熱された状態の初
期において鋼材表面にはＣｒ１Ｆ ｅ ｓ Ｍ ｎから
なるスピネル型主体の酸化スケール層が生成付着するが
、この酸化スケール層は結晶構造的に空隙が多く存在す
るものであるため、酸化スケール層を通しての原子拡散
が容易で、管内を流れる石油系原料との反応界面が常に
鋼材素地表面となるから、石油系原料中の炭素及び酸素
が時間経過に伴って鋼材素地中に拡散浸入して増加する
ことによって生じる、
■ また、前記“管内表面層部のＣｒＱ度が低下してい
る”のは、前述の工程を経て製造した継目無鍛伸鋼管の
表面は、大気雰囲気中での最Ｐ！熱処理時、その表面が
酸化される際に表面層部からのＣｒ移行により高ＣｒＯ
度となった生成付ａ酸化スケール層を脱スケール処理に
よって除去するから、酸化スケール中へのＣｒ移行に伴
って低Ｃｒ濃度となった表面層部が露出したものである
ためである、
■ 一方“ＨＫ４０製の鋳造管には前記■〜■の現象が
ほとんど認められない”のは、鋳造管は鋳込みままでは
表面性吠が不均一であるため、表面を機械加工により均
一にする際、鋳込み後の冷却過程で生成した酸化スケー
ル中へのＣｒ移行に伴ってＣｒ濃度が低下した表面層部
も切削除去されるから、その表面はＣｒ９度低下のない
母材部分が露出したもので、表面層部のＣｒｌＨ度が母
材部分と同一であるためである、
と推定される。Therefore, the present inventors have developed a seamless unforged drawn pipe made of 25Cr-32Ni heat-resistant F14, which was manufactured through the above-mentioned process in a carburizing atmosphere such as an ethylene decomposition furnace, and which is related to the applicant's earlier application. In order to find a means to prevent the occurrence of the above-mentioned "carburization", we conducted research and found that: (1) The oxide scale layer that forms and adheres to the inner surface of the tube is Cr.
The spinel-type oxide consisting of s F c 1M n is the main component; ■ Carburization is common on the inner surface of the pipe where the oxide scale layer has formed and adhered; ■ The inner surface layer of the pipe where the double-sided oxide scale layer has formed and adhered. The following facts were found: Crb of the part: 4 degrees is lower than the Cr concentration of the base metal part; 1) The phenomena of 2 to 3 above are hardly observed in cast pipes made of I-IK40. Based on this fact, ■ In the above-mentioned "carburizing", a spinel-type oxide scale layer consisting mainly of Cr1F e s M n is formed and adhered to the surface of the steel material at the initial stage when it is heated to a high temperature (approximately 1050°C). This oxide scale layer has many voids in its crystal structure, so atoms can easily diffuse through the oxide scale layer, and the reaction interface with the petroleum-based raw material flowing inside the pipe is always the surface of the steel material. This is caused by carbon and oxygen in the system raw materials diffusing and penetrating into the steel material over time and increasing. The surface of the seamless unforged steel pipe manufactured through this process has the highest P in an atmospheric atmosphere! During heat treatment, when the surface is oxidized, high CrO is generated due to Cr migration from the surface layer.
This is because the oxidized scale layer that has become too thick is removed by descaling treatment, and the surface layer that has a low Cr concentration due to Cr migration into the oxide scale is exposed. The reason that "the phenomena described in ■ to ■ above are hardly observed in cast pipes made of HK40" is that the surface roughness of cast pipes is uneven when they are cast, so when making the surface uniform by machining, it is necessary to The surface layer where the Cr concentration has decreased due to the migration of Cr into the oxide scale generated during the subsequent cooling process is also cut away, so the surface is the exposed base material where the Cr concentration has not decreased by 9 degrees. It is presumed that this is because the CrlH degree of the layer part is the same as that of the base material part.
従って、浸炭を防止するには、管内表面層部のＣｒ濃度
をＣｒ、ＦＣ！Ｎ Ｍｎからなるスピネル型の酸化スケ
ール層が生成付着することのない濃度以上にしておけば
、使用時にその表面に生成付着する酸化スケール層が結
晶構造的に空隙の極めて少ないＣｒＭ化物となり、酸化
スケール層を通しての原子拡散が・生じなくなるので耐
浸炭性に優れたものとなるとの知見を得るに到ったので
ある。Therefore, in order to prevent carburization, the Cr concentration in the inner surface layer of the pipe should be adjusted to Cr, FC! If the concentration is higher than that at which a spinel-type oxide scale layer consisting of N Mn does not form or adhere, the oxide scale layer that forms and adheres to the surface during use becomes a CrM compound with extremely few voids in the crystal structure, and the oxide scale They came to the knowledge that since atomic diffusion through the layer does not occur, it has excellent carburization resistance.
本発明は、前記知見に基づいてなされたものであり、
２５Ｃｒ−３２Ｎｉ系耐熱鋼を素材として常法によって
成形された継目無鍛伸鋼管に対して最終の熱処理を非酸
化性雰囲気中で施すことにより、表面層のＣｒ濃度を母
材部のＣｒ２Ｃ２度と実質同一〇［ｆに維持させ、これ
によって使用時の耐浸炭性を確保するようにした点、
に特徴を有するものである。The present invention has been made based on the above-mentioned knowledge, and involves performing a final heat treatment in a non-oxidizing atmosphere on a seamless unforged elongated steel pipe formed by a conventional method using 25Cr-32Ni heat-resistant steel as a raw material. Accordingly, the Cr concentration of the surface layer is maintained at substantially the same Cr2C2 degree of the base material, thereby ensuring carburization resistance during use.
なお、本発明が対象とする２５Ｃｒ−３２Ｎｉ系耐熱鋼
は、本出願人が先に提案した前述の公報に開示される成
分組成のものを対象とするが、望ましくはそのＣｒ含有
量の下限値を２０％以上、更に望ましくは２３％以上と
したものであることが推奨される。The 25Cr-32Ni heat-resistant steel to which the present invention is directed has the composition disclosed in the above-mentioned publication previously proposed by the present applicant, but preferably the lower limit of the Cr content is It is recommended that the amount is 20% or more, more preferably 23% or more.
その理由は、後述する非酸化性雰囲気中での最終熱処理
時に、管内表面層部分のＣｒ濃度を母材部分のＣｒ濃度
と実質同一濃度に確実に維持させ、加熱分解管として使
用した時の加熱昇温過程でその表面に生成付着する酸化
スケール層として雰囲気中との原子拡散が生じない空隙
の極めて少ないＣｒＭ化物からなるものを確実に発生さ
せるためである。The reason for this is that during the final heat treatment in a non-oxidizing atmosphere, which will be described later, the Cr concentration in the inner surface layer of the tube can be maintained at substantially the same concentration as that of the base material. This is to ensure that an oxide scale layer that forms and adheres to the surface during the temperature rising process is made of a CrM compound that has extremely few voids and does not undergo atomic diffusion with the atmosphere.
ところで、本発明に係る製造方法において継目無鍛伸鋼
管は、従来と同様に前述した常法によって所定の形状・
寸法に成形される。そして、この成形された継目無鍛伸
鋼管には、非酸化性雰囲気中での最終の熱処理が施され
、その後必要に応じて脱スケール処理されて製品とされ
る。By the way, in the manufacturing method according to the present invention, the seamless unforged steel pipe is formed into a predetermined shape and shape by the conventional method as described above.
Shaped to size. The formed seamless unforged drawn steel pipe is then subjected to a final heat treatment in a non-oxidizing atmosphere, and then subjected to descaling treatment as required to produce a product.
最終の熱処理を施す非酸化性雰囲気としては、中性又は
環元性ガス（水素、アルゴン、窒素等）のガス単体又は
混合ガスを用い、ガス１００％の雰囲気とするのが最も
望ましい。しかし、母材のＣｒｅ度が充分高く、熱処理
後において表面層部分のＣｒ濃度を２０％以上、好まし
くは２３％以上に保ちうる場合には若干の酸素が混入し
た雰囲気であってもよい。なお、この混入してもよい酸
素口は、母材のＣｒｅ度との関連で定まる。As the non-oxidizing atmosphere in which the final heat treatment is performed, it is most desirable to use a neutral or cyclic gas (hydrogen, argon, nitrogen, etc.) alone or in a mixture, and to create an atmosphere of 100% gas. However, if the Cr degree of the base material is sufficiently high and the Cr concentration in the surface layer portion can be maintained at 20% or more, preferably 23% or more after heat treatment, an atmosphere containing some oxygen may be used. Note that this oxygen port that may be mixed is determined in relation to the Cre degree of the base material.
また、本発明、における前記非酸化性雰囲気中での最終
の熱処理は、従来と同様に、所定の強度、金属組織を得
るための溶体化処理を目的として施されるが、鋼管を望
ましくは常潟から、少なくともＣｒの酸化が開始する５
００℃以上においては非酸化性雰囲気中に位置させ、１
２００〜１２５０℃の温度域に加熱昇温し、次いで３〜
１０分間均熱保持して後、水冷又は空冷することによっ
て施される。Further, the final heat treatment in the non-oxidizing atmosphere in the present invention is performed for the purpose of solution treatment to obtain a predetermined strength and metallographic structure, as in the conventional method, but desirably the steel pipe is Oxidation of at least Cr starts from the lagoon5
At temperatures above 00°C, place in a non-oxidizing atmosphere,
Heating to a temperature range of 200 to 1250°C, then heating to a temperature range of 3 to 1250°C
It is applied by soaking for 10 minutes and then cooling with water or air.
すなわち、熱処理温度を１２００〜１２５０℃とするの
は、１２００°Ｃ未満であると目的とする高温強度が得
られないからであり、１２５０℃を越えると結晶粒が粗
大化し、溶接性が悪くなるからである。In other words, the heat treatment temperature is set at 1200 to 1250°C because if it is less than 1200°C, the desired high-temperature strength cannot be obtained, and if it exceeds 1250°C, the crystal grains will become coarse and weldability will deteriorate. It is from.
また、均熱保持時間を３〜１０分間とするのは、３分未
満であると溶体化が不充分となるからであり、１０分を
越えると効果が飽和し、不経済である。The reason why the soaking time is set to 3 to 10 minutes is because if it is less than 3 minutes, the solutionization will be insufficient, and if it exceeds 10 minutes, the effect will be saturated and it will be uneconomical.
なお、前記熱処理は、熱処理後における脱スケール処理
工程を省略して表面性吠の優れた製品が得られ、かつそ
の処理能率の向上を目的とし、鋼管の如き長尺の材料を
非酸化性雰囲気中で連続的に処理する工業用の炉として
、例えば、両端開口の筒伏マツフル内に水素ガスを充滴
させる一方、このマツフル中を輪転駆動する無端のメツ
シュベルト上に鋼管を載置して搬送挿通させ、マツフル
外から加熱する構造からなる周知の所謂水素炉を用いて
高能率に施すことができる。しかし、水素炉にその構成
部材である前記マツフル、メツシュベルト等が、通常、
高々１１００℃に耐える程度の耐熱性を存する材料で設
計されているのに過ぎないから、前述した高温域での熱
処理を実施した場合には炉寿命が低下する。The above heat treatment is performed by omitting the descaling process after the heat treatment to obtain a product with excellent surface texture, and with the aim of improving the processing efficiency. As an industrial furnace for continuous processing inside, for example, hydrogen gas is filled in a matsufuru with open ends at both ends, and a steel pipe is placed on an endless mesh belt that is rotatably driven through this matsufuru and transported. The treatment can be carried out with high efficiency using a well-known so-called hydrogen furnace, which has a structure in which it is inserted through the pine tree and heated from outside. However, the components such as Matsufuru, Metschbelt, etc. that are included in the hydrogen reactor are usually
Since the furnace is designed using a material that has heat resistance that can withstand temperatures of at most 1100° C., the life of the furnace will be shortened if the heat treatment is performed in the above-mentioned high temperature range.
したがって、加熱分解管に要求される耐浸炭性は管内面
であることから、前記ガスを管内に封入するか、又は流
通させながら実施するのが望ましい。なお、ガスを管内
に封入又は流通させて熱処理を実施する場合には、管外
面にＦｅｓ Ｍｎ１Ｃｒからなるスピネル型の酸化スケ
ールが生成付着することとなるが、この酸化スケールは
加熱分解管としては付着していても何等問題となること
はない。Therefore, since the carburization resistance required for the pyrolysis tube is on the inner surface of the tube, it is desirable to seal the gas in the tube or to carry out the process while circulating the gas. In addition, when heat treatment is performed by sealing or circulating gas inside the tube, a spinel-type oxide scale consisting of FesMn1Cr will form and adhere to the outer surface of the tube, but this oxide scale will not adhere to the tube as a thermal decomposition tube. Even if you do, there will be no problem.
しかし、製品の商品価値上、見ばえ等が劣って問題とな
る場合には、例えばシｑットブラスト等の適宜な機械的
手段あるいは弗硝酸酸洗等の化学的手段によって除去し
、その商品価値を高めた製品となるようにすればよい。However, if the product's appearance is inferior and becomes a problem in terms of its commercial value, it can be removed by appropriate mechanical means such as Shiqt blasting or chemical means such as fluoro-nitric acid pickling to reduce its commercial value. What is necessary is to create a product with a high level of quality.
次に、本発明を、実施例により従来例と対比して説明す
る。Next, the present invention will be explained using examples in comparison with a conventional example.
先ず、第１表に示す成分組成の鋼を素材とし、熱間押出
し製管法によって内外面が共に平滑な外径１１４．０ｍ
ｍ、肉厚ａ ５ ｓｗ＋の継目無鍛伸鋼管を成形して後
、第２表に示す各条件で夫々最終の熱処理を管内ガス封
入法によって施した。First, steel with the composition shown in Table 1 was used as a material, and a pipe with an outer diameter of 114.0 m was made with smooth inner and outer surfaces by hot extrusion.
After forming a seamless unforged drawn steel pipe with a wall thickness of 5 sw+ and a wall thickness of 5 sw+, a final heat treatment was performed under each of the conditions shown in Table 2 by an in-pipe gas filling method.
戸１表
次いで、これら鋼管から供試片を切り出し、容量比で木
炭７０％、Ｂ ａ ＣＯ３粉末３０％であり、温度１０
５０℃及び１１００℃の浸炭雰囲気中に夫々１０時間放
置し、耐浸炭性を調査した結果を、熱処理後における管
内面表層部のＣｒ濃度と共に、第２表に併せて示す。Next, test pieces were cut out from these steel pipes, and the volume ratio was 70% charcoal and 30% B a CO3 powder, and the temperature was 10%.
The results of investigating the carburization resistance by leaving the tubes in carburizing atmospheres at 50° C. and 1100° C. for 10 hours, respectively, are shown in Table 2 together with the Cr concentration in the surface layer of the inner surface of the tube after heat treatment.
なお、耐浸炭性は管内表面からα５龍までの表層部分の
炭素増加量をもって示しである。Note that carburization resistance is indicated by the amount of carbon increase in the surface layer from the inner surface of the pipe to the α5 dragon.
第 ２ 表
第２表に示される結果から明らかなように、本発明の製
造方法によって製造された継目無鍛伸鋼管は、耐浸炭性
が各段に優れるものであることが明らかである。Table 2 As is clear from the results shown in Table 2, it is clear that the seamless drawn steel pipe produced by the production method of the present invention has excellent carburization resistance.
以上に説明したように、本発明によれば、浸炭雰囲気中
で使用して極めて耐浸炭性に優れた高温強度等に問題の
ない継目無鍛伸ｆＩ４管を安定して供給することができ
るから、安全性が最重要の化学工業用装置たるエチレン
分解炉等の信頼性をより一層向上させることが可能とな
る。As explained above, according to the present invention, it is possible to stably supply seamless unforged elongated fI4 pipe that is used in a carburizing atmosphere and has excellent carburization resistance and no problems in high temperature strength etc. This makes it possible to further improve the reliability of ethylene decomposition furnaces, etc., which are chemical industrial equipment where safety is of the utmost importance.
Claims (1)
成形された継目無鍛伸鋼管に対して最終の熱処理を非酸
化性雰囲気中で施すことにより、表面層のＣｒ濃度を母
材部のＣｒ濃度と実質同一濃度に維持させることを特徴
とする耐浸炭性に優れた継目無鍛伸鋼管の製造方法。By applying final heat treatment to a seamless unforged drawn steel pipe formed by a conventional method using 25Cr-32Ni heat-resistant steel as a raw material in a non-oxidizing atmosphere, the Cr concentration in the surface layer can be adjusted to match the Cr concentration in the base material. A method for producing a seamless drawn steel pipe with excellent carburization resistance, characterized by maintaining substantially the same concentration.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1509988A JPH01191740A (en) | 1988-01-25 | 1988-01-25 | Production of seamless extend-forged steel pipe having excellent carburization resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1509988A JPH01191740A (en) | 1988-01-25 | 1988-01-25 | Production of seamless extend-forged steel pipe having excellent carburization resistance |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH01191740A true JPH01191740A (en) | 1989-08-01 |
Family
ID=11879395
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1509988A Pending JPH01191740A (en) | 1988-01-25 | 1988-01-25 | Production of seamless extend-forged steel pipe having excellent carburization resistance |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH01191740A (en) |
-
1988
- 1988-01-25 JP JP1509988A patent/JPH01191740A/en active Pending
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