JPH0579734B2 - - Google Patents
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- Publication number
- JPH0579734B2 JPH0579734B2 JP62321333A JP32133387A JPH0579734B2 JP H0579734 B2 JPH0579734 B2 JP H0579734B2 JP 62321333 A JP62321333 A JP 62321333A JP 32133387 A JP32133387 A JP 32133387A JP H0579734 B2 JPH0579734 B2 JP H0579734B2
- Authority
- JP
- Japan
- Prior art keywords
- strength
- temperature
- steel
- manufacturing
- corrosion resistance
- 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 - Lifetime
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- 229910000831 Steel Inorganic materials 0.000 claims description 44
- 239000010959 steel Substances 0.000 claims description 44
- 230000007797 corrosion Effects 0.000 claims description 26
- 238000005260 corrosion Methods 0.000 claims description 26
- 238000004519 manufacturing process Methods 0.000 claims description 18
- 238000010438 heat treatment Methods 0.000 claims description 9
- 238000005098 hot rolling Methods 0.000 claims description 8
- 238000012545 processing Methods 0.000 claims description 5
- 238000005096 rolling process Methods 0.000 claims description 2
- 229910001562 pearlite Inorganic materials 0.000 description 20
- 229910000859 α-Fe Inorganic materials 0.000 description 17
- 238000012360 testing method Methods 0.000 description 10
- 238000005336 cracking Methods 0.000 description 9
- 230000000694 effects Effects 0.000 description 7
- 239000000463 material Substances 0.000 description 5
- 229910052799 carbon Inorganic materials 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 150000001247 metal acetylides Chemical class 0.000 description 4
- 238000000034 method Methods 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 230000001376 precipitating effect Effects 0.000 description 3
- 238000005496 tempering Methods 0.000 description 3
- 229910000851 Alloy steel Inorganic materials 0.000 description 2
- 229910000967 As alloy Inorganic materials 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 238000000137 annealing Methods 0.000 description 2
- 229910001563 bainite Inorganic materials 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 229910000734 martensite Inorganic materials 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 239000002436 steel type Substances 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- 238000005452 bending Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 230000003009 desulfurizing effect Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 230000004580 weight loss Effects 0.000 description 1
Landscapes
- Heat Treatment Of Steel (AREA)
Description
〈産業上の利用分野〉
本発明は、耐食性ならびに溶接性に優れた高強
度Cr−Mo継目無鋼管の製造方法に係り、特に高
温で使用されるボイラなどの熱交換器用鋼管や化
学工業用プラントの加熱器管，熱交換器管などに
用いるのに好適な、耐食性ならびに溶接性に優れ
た高温で高強度を有するCr−Mo継目無鋼管の製
造方法に関する。
〈従来の技術〉
Cr−Mo鋼は、一般に、焼入れ性がよく、その
うえ焼戻しに対する抵抗性も大きく、焼戻しぜい
性の傾向も少ないので、機械構造用合金鋼として
盛んに使用されている。また、このCr−Mo鋼
は、高温強度やクリープ強度が普通鋼より高いこ
とから高温用途にも使用されている。
従来から、高温用途にも使用されているCr−
Mo鋼は、例えばボイラなどの熱交換器用合金鋼
鋼管として、STBA12，STBA13，STBA20，
STBA22，TSBA23，STBA24，STBA25，
STBA26がJIS化されており、このうちSTBA24
は、21／4Cr−1Mo鋼と呼ばれ、上記鋼種の中で
は最も高い高温強度を有する鋼として知られてい
る。
高温用途には、上記ボイラなどの熱交換器用以
外に化学工業用プラント類の配管用としても同種
の鋼管が使用され、配管用合金鋼管としては
STPA12〜26がJIS化されている。
上記の鋼管類は、現状では製造性や高温強度の
点ではかなりバランスのとれた特性を有している
が、合金鋼鋼管としては、より一層の高温強度を
有し、さらに溶接性や耐食性が向上することが望
まれていた。すなわち、鋼管類は、使用に当たつ
て溶接施工が必須であり、溶接時の割れ感受性の
低減やさらに鋼管の安全性，寿命の点から耐食性
の向上が求められていたのである。
〈発明が解決しようとする問題点〉
従来の21／4Cr−1Moや5Cr−0.5Mo，9Cr−
1MoなどのCr−Mo鋼は、製造後等温焼きなまし
または焼きならし後焼戻しあるいは完全焼きなま
しなどの熱処理を施した後使用される。このと
き、組織はフエライト・パーライトや焼戻された
マルテンサイトやベイナイトを含むフエライト・
パーライト相である。上述のような熱処理を受け
るCr−Mo鋼の場合、耐食性や溶接性の向上を図
るべく低Ｃ化すると、軟化して強度低下してしま
うという問題点があつた。
本発明は、上記のような問題点を解決すべくな
されたものであつて、低Ｃ化しても強度特に高温
強度の低下がなく、かつ、耐食性や溶接性に優れ
たCr−Mo継目無鋼管の製造方法を提供すること
を目的とする。
〈問題点を解決するための手段〉
溶接性や耐食性は、Ｃ量を低減すると向上する
ことはよく知られている。高温用鋼として使用す
るためには、常温から高温の強度が高いほど望ま
しいことは言うまでもない。しかもミクロ組織の
観点からは、熱的に不安定なマルテンサイト相や
ベイナイト相は焼き戻されていることが必要であ
り、フエライト・パーライト相の方がより安定で
あるので、高温強度を下げないでフエライト・パ
ーライト相が多くできる方がよい。
本発明者らは、上記のような特性を得るべく鋭
意研究を行つた結果、Ｃ量などの成分範囲や製造
条件，熱処理条件を見出し、その知見に基づいて
本発明を完成させるに至つた。
すなわち、本発明の第１の態様は、重量％で、
Ｃ：0.04〜0.09％，Si：1.0％以下，Mn：0.2〜0.8
％，Cr：1.90〜7.50％，Mo：0.40〜1.20％を含有
するCr−Mo継目無鋼管を熱間圧延工程で製造す
るに際し、750〜1000℃の温度で断面減少率10％
以上の加工歪みを与えて圧延することを特徴とす
る耐食性ならびに溶接性に優れた高強度Cr−Mo
継目無鋼管の製造方法である。
また、本発明の第２の態様は、重量％で、Ｃ：
0.04〜0.09％，Si：1.0％以下，Mn：0.2〜0.8％，
Cr：1.90〜7.50％，Mo：0.40〜1.20％を含有する
Cr−Mo継目無鋼管を熱間圧延工程で製造するに
際し、750〜1000℃の温度で断面減少率10％以上
の加工歪みを与えて圧延し、ついで700〜800℃で
５〜60分の熱処理を施すことを特徴とする耐食性
ならびに溶接性に優れた高強度Cr−Mo継目無鋼
管の製造方法である。
〈作用〉
本発明者らは、適量のＣ量を含有した鋼に熱間
で適切な加工歪みを加えることにより、組織的に
はより安定であるフエライト・パーライト相が誘
起されてアズロールでフエライト・パーライト相
が得られ、しかも熱間加工時に生じた歪みに炭化
物が微細に析出することにより、常温ならびに高
温での強度を著しく高めることができることを見
出した。
以下に、この知見を得た実験結果について説明
する。
第１図は、Ｃ：0.08％（重量％，以下同じ），
Si：0.4％，Mn：0.6％，Cr：5.0％，Mo：0.50％
鋼を用いて、熱間圧延時の断面減少率が40％で、
そのときの熱間加工温度を700〜1050℃に変えた
ときのフエライト・パーライト発生率およびビツ
カース硬さを示したものである。図から明らかな
ように、750〜1000℃の温度範囲でフエライト・
パーライト相の発生率が高く、しかもビツカース
硬さは低くなつている。
一方、第２図には、同じ成分の鋼について熱間
加工温度800℃のとき、断面減少率を５〜90％と
変えて熱間加工した場合のフエライト・パーライ
ト発生率およびビツカース硬さを示したものであ
る。図から分かるように、断面減少率が10％以上
でフエライト・パーライトの発生率が高くなり、
ビツカース硬さも低くなつている。
このような実験結果から明らかなように、組織
的により安定であるフエライト・パーライト相と
常温ならびに高温における高い強度を同時に得る
ためには、熱間圧延工程における圧下率が断面減
少率で10％以上は必要であり、さらに加工温度が
750〜1000℃の範囲であることが必要である。
さらに、場合によつては、熱間圧延に引き続い
て700〜800℃で熱処理を施すことにより、圧延時
に生じた加工歪みを低減させて耐食性の向上を図
るとともに、加工歪みを有する組織に炭化物を析
出させて熱処理による強度低下を補い、高強度を
維持させることが可能である。
ここで、熱処理温度の制限理由は、700℃未満
では上記作用への効果が弱いため長時間必要であ
り、実用的長さと考えられる１時間以上必要とな
るため、下限を700℃とした。また、本発明の対
象鋼種ではAC1が800℃を若干上回る付近にある
ため、800℃を超えると熱処理時に変態を生ずる
恐れがあるので上限を800℃とした。
つぎに、各化学成分の限定理由について説明す
る。
Ｃ：
Ｃは、固溶硬化ならびに炭化物の形成・析出に
より、常温や高温強度を確保するのに必須の元素
である。適切なＣ含有量に加えて上記したような
熱間加工条件とが相関しあつて、安定なフエライ
ト・パーライト相と常温ならびに高温における高
い強度を同時に得る特性を達成するのであるが、
十分な強度を得るためには、少なくとも0.04％は
必要である。
つぎに、供試材として、21／4Cr−1Mo鋼，
5Cr−0.5Mo鋼，9Cr−1Mo鋼を用いて、Ｃ量と
溶接時の耐高温割れ性との関係をトランスバレス
トレイン試験による割れ長さについて調査した。
その結果は、第３図に示すように、Ｃ含有量が
0.09％以下で耐割れ性が大きく改善されることが
分かつた。さらに、Ｃ含有量と耐食性との関係に
ついては、Cr−Mo鋼がH2S環境下で使用される
ケースも多いので、H2Sガスを含む耐食性試験と
してNACE液中での腐食試験を行つた。その結
果は、第４図に示すように、Ｃ含有量が0.09％以
下で急激に腐食量が減少することが分かつた。
これらのことから、したがつてＣ含有量は0.04
〜0.09％の範囲に限定するのが必要である。
Si：
Siは、脱酸剤として添加するが、多量に用いる
と鋼の靭性が劣化するので上限を1.00％とする。
なお、高温長時間強度と靭性向上のためには、Si
を下げた方がよいので下限は規定しない。
Mn：
Mnは、脱酸や脱硫剤として、また強度や熱間
加工性を改善して適正な組織を得るために有用な
元素であるが、この効果を発揮させるためには
0.2％以上の添加が必要である。一方、0.8％を超
えると焼入れ性が高くなり強度が増すが、曲げな
どの加工性や靭性の劣化を招くので、その必要範
囲を0.2〜0.8％とする。
Cr：
Crは、焼入れ性を増し、焼戻しに対する抵抗
性を大きくする効果があり、常温ならびに高温に
おける強度を向上させる。この効果を発揮させる
ためには、1.90％以上の添加が必要である。一
方、Crが多くなると焼入れ性が増し、熱間圧延
時にフエライト・パーライト組織を得るのが困難
となる。本発明の製造条件で適正なフエライト・
パーライト組織を得るためには、Cr量を7.5％以
下にする必要がある。
Mo：
Moは、鋼中に固溶したり炭化物を析出して常
温ならびに高温における強度を向上させる効果が
大きいが、0.40％未満のMoではこの効果がない。
一方、1.20％を超えるとその効果が飽和傾向を示
し、しかもMoは高価な元素なのでその上限を
1.20％とした。
〈実施例〉
供試材として、第１表に示すＡ〜Ｆの６種の本
発明の成分を有するCr−Mo鋼を用いて、第２表
に示す製造条件で継目無鋼管を製造した。なお、
比較のために、供試材として、第１表に併せて示
すＧ〜Ｉの３種の従来成分のCr−Mo鋼を用いて
継目無鋼管の製造も行つた。
第２表の製造条件において、実験No.１〜16は本
発明例、No.17〜23は比較例、No.24，25は従来の製
造例である。
本発明例中、実験No.３，９，11は、熱間圧延後
熱処理を施したものである。
比較例について、本発明例の条件を満足してい
ない項目は、＊印で示したが、No.17，20は仕上温
度が1000℃を超えた例、No.18は仕上温度が下限の
750℃を下回つた例、No.19は断面減少率が10％を
下回つた例、No.21〜23は鋼成分のＣ含有量が本発
明の成分範囲の上限を超えた例、No.24，25はＣ含
<Industrial Application Field> The present invention relates to a method for manufacturing high-strength Cr-Mo seamless steel pipes with excellent corrosion resistance and weldability, and is particularly applicable to steel pipes for heat exchangers such as boilers used at high temperatures, and chemical industrial plants. This invention relates to a method for manufacturing Cr-Mo seamless steel pipes that have excellent corrosion resistance and weldability and have high strength at high temperatures, and are suitable for use in heater tubes, heat exchanger tubes, etc. <Prior Art> Cr-Mo steel generally has good hardenability, high resistance to tempering, and little tendency to temper brittleness, so it is widely used as an alloy steel for machine structures. Furthermore, this Cr-Mo steel is also used for high-temperature applications because it has higher high-temperature strength and creep strength than ordinary steel. Cr-, which has traditionally been used for high-temperature applications.
Mo steel is used as alloy steel pipes for heat exchangers such as boilers, such as STBA12, STBA13, STBA20,
STBA22, TSBA23, STBA24, STBA25,
STBA26 has been standardized as JIS, of which STBA24
is called 21/4Cr-1Mo steel and is known to have the highest high temperature strength among the above steel types. For high-temperature applications, the same type of steel pipes are used not only for heat exchangers such as the boilers mentioned above, but also for piping in chemical industrial plants, and as alloy steel pipes for piping.
STPA12 to 26 have been converted to JIS. The above-mentioned steel pipes currently have fairly well-balanced characteristics in terms of manufacturability and high-temperature strength, but alloy steel pipes have even higher high-temperature strength, as well as better weldability and corrosion resistance. It was hoped that it would improve. In other words, steel pipes must be welded in order to be used, and there has been a need to reduce the susceptibility to cracking during welding and to improve corrosion resistance from the standpoint of safety and longevity of the steel pipes. <Problems to be solved by the invention> Conventional 21/4Cr-1Mo, 5Cr-0.5Mo, 9Cr-
Cr-Mo steel such as 1Mo is used after being subjected to heat treatment such as isothermal annealing, normalizing and tempering, or complete annealing after manufacturing. At this time, the structure is ferrite/pearlite or ferrite/pearlite containing tempered martensite or bainite.
It is pearlite phase. In the case of Cr-Mo steel that undergoes heat treatment as described above, there is a problem in that when lowering the carbon content in order to improve corrosion resistance and weldability, the steel softens and its strength decreases. The present invention was made to solve the above-mentioned problems, and provides a Cr-Mo seamless steel pipe that does not deteriorate in strength, especially high-temperature strength, even when carbon is reduced, and has excellent corrosion resistance and weldability. The purpose is to provide a manufacturing method for. <Means for solving the problem> It is well known that weldability and corrosion resistance are improved by reducing the amount of C. Needless to say, in order to use the steel as a high-temperature steel, the higher the strength from room temperature to high temperature, the more desirable it is. Moreover, from a microstructural perspective, the thermally unstable martensite and bainite phases need to be tempered, and the ferrite/pearlite phases are more stable, so high-temperature strength is not reduced. It is better if more ferrite/pearlite phases are formed. The present inventors conducted intensive research to obtain the above characteristics, and as a result, discovered the range of components such as the amount of C, manufacturing conditions, and heat treatment conditions, and completed the present invention based on these findings. That is, in the first aspect of the present invention, in weight %,
C: 0.04-0.09%, Si: 1.0% or less, Mn: 0.2-0.8
%, Cr: 1.90-7.50%, Mo: 0.40-1.20% When manufacturing Cr-Mo seamless steel pipes using a hot rolling process, the area reduction rate is 10% at a temperature of 750-1000℃.
High-strength Cr-Mo with excellent corrosion resistance and weldability, characterized by being rolled with a processing strain of
This is a method for manufacturing seamless steel pipes. Moreover, the second aspect of the present invention provides, in weight %, C:
0.04-0.09%, Si: 1.0% or less, Mn: 0.2-0.8%,
Contains Cr: 1.90-7.50%, Mo: 0.40-1.20%
When manufacturing Cr-Mo seamless steel pipes through a hot rolling process, they are rolled at a temperature of 750 to 1000°C with a processing strain of 10% or more in area reduction, and then heat treated at 700 to 800°C for 5 to 60 minutes. This is a method for manufacturing high-strength Cr-Mo seamless steel pipes with excellent corrosion resistance and weldability. <Function> The present inventors have discovered that by applying hot working strain to steel containing an appropriate amount of C, the ferrite/pearlite phase, which is structurally more stable, is induced and the ferrite/pearlite phase is formed in azurol. It has been found that by obtaining a pearlite phase and finely precipitating carbides in the strain caused during hot working, the strength at room temperature and high temperature can be significantly increased. The experimental results from which this knowledge was obtained will be explained below. Figure 1 shows C: 0.08% (weight%, same below),
Si: 0.4%, Mn: 0.6%, Cr: 5.0%, Mo: 0.50%
Using steel, the cross-section reduction rate during hot rolling is 40%,
The graph shows the ferrite/pearlite generation rate and Vickers hardness when the hot working temperature was changed from 700 to 1050°C. As is clear from the figure, ferrite and
The occurrence rate of pearlite phase is high, and the Vickers hardness is low. On the other hand, Figure 2 shows the ferrite/pearlite generation rate and Bitkers hardness when steel with the same composition is hot worked at a hot working temperature of 800°C and the area reduction rate is varied from 5 to 90%. It is something that As can be seen from the figure, when the cross-sectional reduction rate is 10% or more, the occurrence rate of ferrite and pearlite increases.
Bitker's hardness has also decreased. As is clear from these experimental results, in order to simultaneously obtain the structurally more stable ferrite/pearlite phase and high strength at room and high temperatures, the reduction rate in the hot rolling process must be 10% or more in area reduction rate. is necessary, and the processing temperature is
It is necessary that the temperature is in the range of 750 to 1000°C. Furthermore, in some cases, hot rolling is followed by heat treatment at 700 to 800°C to reduce the working strain caused during rolling and improve corrosion resistance, and to add carbides to the strained structure. By precipitating it, it is possible to compensate for the decrease in strength due to heat treatment and maintain high strength. Here, the reason for limiting the heat treatment temperature is that if it is lower than 700°C, the effect on the above action is weak and a long time is required, and more than 1 hour, which is considered to be a practical length, is required, so the lower limit was set at 700°C. In addition, in the steel types targeted by the present invention, A C1 is around slightly above 800°C, so if it exceeds 800°C, transformation may occur during heat treatment, so the upper limit was set at 800°C. Next, the reasons for limiting each chemical component will be explained. C: C is an essential element for ensuring strength at room temperature and high temperature through solid solution hardening and formation/precipitation of carbides. In addition to the appropriate C content, the above-mentioned hot working conditions are correlated to achieve properties that simultaneously provide a stable ferrite/pearlite phase and high strength at room and high temperatures.
At least 0.04% is required to obtain sufficient strength. Next, as test materials, 21/4Cr-1Mo steel,
Using 5Cr-0.5Mo steel and 9Cr-1Mo steel, the relationship between C content and hot cracking resistance during welding was investigated using a transvalle strain test to investigate the crack length.
As shown in Figure 3, the results show that the C content is
It was found that the cracking resistance was greatly improved when the content was 0.09% or less. Furthermore, regarding the relationship between C content and corrosion resistance, since Cr-Mo steel is often used in an H 2 S environment, a corrosion test in NACE liquid was conducted as a corrosion resistance test containing H 2 S gas. Ivy. As shown in FIG. 4, the results showed that the amount of corrosion decreased rapidly when the C content was 0.09% or less. From these facts, the C content is therefore 0.04
It is necessary to limit the content to a range of ~0.09%. Si: Si is added as a deoxidizing agent, but if used in large amounts, the toughness of the steel will deteriorate, so the upper limit is set at 1.00%.
In addition, in order to improve high-temperature long-term strength and toughness, Si
It is better to lower the value, so no lower limit is specified. Mn: Mn is a useful element as a deoxidizing and desulfurizing agent, as well as for improving strength and hot workability and obtaining an appropriate structure.
It is necessary to add 0.2% or more. On the other hand, if it exceeds 0.8%, hardenability increases and strength increases, but it causes deterioration of workability such as bending and toughness, so the necessary range is set to 0.2 to 0.8%. Cr: Cr has the effect of increasing hardenability and resistance to tempering, and improves strength at room temperature and high temperature. In order to exhibit this effect, it is necessary to add 1.90% or more. On the other hand, as the Cr content increases, the hardenability increases, making it difficult to obtain a ferrite-pearlite structure during hot rolling. Appropriate ferrite and
In order to obtain a pearlite structure, the Cr content must be 7.5% or less. Mo: Mo has a great effect of improving the strength at room temperature and high temperature by forming a solid solution in steel or precipitating carbides, but Mo less than 0.40% does not have this effect.
On the other hand, if the concentration exceeds 1.20%, the effect tends to be saturated, and since Mo is an expensive element, the upper limit cannot be reached.
It was set at 1.20%. <Example> Seamless steel pipes were manufactured under the manufacturing conditions shown in Table 2 using Cr-Mo steel having six types of ingredients of the present invention, A to F shown in Table 1, as test materials. In addition,
For comparison, seamless steel pipes were also manufactured using three conventional Cr-Mo steels, G to I, shown in Table 1, as test materials. Regarding the manufacturing conditions in Table 2, Experiment Nos. 1 to 16 are examples of the present invention, Nos. 17 to 23 are comparative examples, and Nos. 24 and 25 are conventional manufacturing examples. Among the examples of the present invention, Experiment Nos. 3, 9, and 11 were subjected to heat treatment after hot rolling. Regarding comparative examples, items that do not satisfy the conditions of the present invention example are marked with an asterisk, but Nos. 17 and 20 are examples where the finishing temperature exceeds 1000℃, and No. 18 is an example where the finishing temperature is at the lower limit.
No. 19 is an example where the area reduction rate was less than 10%, and No. 21 to 23 are examples where the C content of the steel component exceeded the upper limit of the composition range of the present invention. .24 and 25 contain C.
【表】
有量が本発明の成分範囲の上限を超えて、かつ従
来法で製造した例である。
上記の各種の製造条件による各実験材の機械的
性質，耐食性および溶接割れ性をそれぞれ調査し
て、それらの結果を第２表に併せてて示した。
なお、耐食性はNACE液中で腐食試験を行い、
そのときの腐食減量で評価した。この腐食試験
は、純水に５％NaClと0.5％の酢酸を混合させ、
さらに１気圧でH2Sを飽和させた25℃の液に10日
間浸漬して行つたものである。
また、溶接割れ性の評価はトランスバレストレ
イン試験による割れ長さ（mm）で評価した。フエ
ライト・パーライト率（％）はミクロ組織観察を
行い、面積率を求めたものである。
第２表において、本発明例は従来例と比較して
いずれも耐食性，溶接割れ性が改善されており、
しかも常温強度および高温強度とも著しく高い値
であり、高温強度が常温強度より若干高いかほぼ
同等の値を有する特徴が示されている。
一方、本発明の条件を満足しない比較例は、い
ずれも本発明と比較して高強度は確保できている
ものの、フエライト・パーライト率は著しく低く
組織的に不適当である。特に、No.21〜25のＣ含有
量の高い鋼種では、本発明例より耐食性，溶接割
れ性が劣つている。[Table] This is an example in which the amount exceeds the upper limit of the component range of the present invention and was produced using a conventional method. The mechanical properties, corrosion resistance, and weld cracking resistance of each experimental material under the various manufacturing conditions described above were investigated, and the results are also shown in Table 2. In addition, corrosion resistance was determined by conducting a corrosion test in NACE liquid.
Evaluation was made based on the corrosion loss at that time. This corrosion test involves mixing 5% NaCl and 0.5% acetic acid in pure water.
The specimen was then immersed in a 25°C solution saturated with H 2 S at 1 atm for 10 days. In addition, the weld cracking property was evaluated using the crack length (mm) by transvale strain test. The ferrite/pearlite ratio (%) is obtained by observing the microstructure and determining the area ratio. In Table 2, the examples of the present invention have improved corrosion resistance and weld cracking resistance compared to the conventional examples.
Moreover, both the room temperature strength and the high temperature strength are extremely high values, indicating that the high temperature strength is either slightly higher than the room temperature strength or almost the same value. On the other hand, in all of the comparative examples that do not satisfy the conditions of the present invention, although higher strength is ensured compared to the present invention, the ferrite/pearlite ratio is extremely low and the structure is inappropriate. In particular, steel grades No. 21 to 25 with a high C content are inferior to the examples of the present invention in corrosion resistance and weld cracking resistance.
【表】【table】
【表】
〈発明の効果〉
以上説明したように、本発明によれば、従来の
製法で不可能であつたCr−Mo継目無鋼管の高強
度化に加えて耐食性および溶接割れ性の向上が同
時に実現可能となつた。
しかも、高温強度も常温強度と同程度に高い値
を有するから、耐食性，溶接割れ性が従来より向
上して高温で著しく高強度が得られ、ボイラなど
の熱交換器用や化学工業プラント用として、従来
材に比較して薄肉化が可能であり、また施工性や
耐久性を大幅に改善することが可能である。[Table] <Effects of the invention> As explained above, according to the present invention, in addition to increasing the strength of Cr-Mo seamless steel pipes, which was impossible with conventional manufacturing methods, it is possible to improve corrosion resistance and weld cracking resistance. It became possible at the same time. Moreover, the high temperature strength is as high as the normal temperature strength, so corrosion resistance and weld cracking resistance are improved compared to conventional ones, and significantly high strength can be obtained at high temperatures, making it suitable for use in heat exchangers such as boilers and chemical industrial plants. Compared to conventional materials, it is possible to make the wall thinner, and it is also possible to significantly improve workability and durability.
第１図は、熱間加工温度とフエライト・パーラ
イト発生率およびビツカース硬さとの関係を示す
特性図、第２図は、断面減少率とフエライト・パ
ーライト発生率およびビツカース硬さとの関係を
示す特性図、第３図は、Ｃ含有量とトランスバレ
ストレイン試験による割れ長さの関係を示す特性
図、第４図は、Ｃ含有量とNACE液中での腐食
減量の関係を示す特性図である。
Figure 1 is a characteristic diagram showing the relationship between hot working temperature, ferrite/pearlite generation rate, and Vickers hardness, and Figure 2 is a characteristic diagram showing the relationship between area reduction rate, ferrite/pearlite generation rate, and Vickers hardness. , FIG. 3 is a characteristic diagram showing the relationship between C content and crack length by transvalle strain test, and FIG. 4 is a characteristic diagram showing the relationship between C content and corrosion weight loss in NACE liquid.
Claims (1)
製造するに際し、750〜1000℃の温度で断面減少
率10％以上の加工歪みを与えて圧延することを特
徴とする耐食性ならびに溶接性に優れた高強度
Cr−Mo継目無鋼管の製造方法。 ２ 重量％で、 Ｃ：0.04〜0.09％，Si：1.0％以下， Mn：0.2〜0.8％，Cr：1.90〜7.50％， Mo：0.40〜1.20％ を含有するCr−Mo継目無鋼管を熱間圧延工程で
製造するに際し、750〜1000℃の温度で断面減少
率10％以上の加工歪みを与えて圧延し、ついで
700から800℃で５〜60分の熱処理を施すことを特
徴とする耐食性ならびに溶接性に優れた高強度
Cr−Mo継目無鋼管の製造方法。[Claims] Cr-Mo containing 1% by weight: C: 0.04-0.09%, Si: 1.0% or less, Mn: 0.2-0.8%, Cr: 1.90-7.50%, Mo: 0.40-1.20% When manufacturing seamless steel pipes using a hot rolling process, they are rolled at a temperature of 750 to 1000°C with a processing strain of 10% or more in area reduction, resulting in high strength with excellent corrosion resistance and weldability.
Manufacturing method of Cr-Mo seamless steel pipe. 2. A Cr-Mo seamless steel pipe containing C: 0.04 to 0.09%, Si: 1.0% or less, Mn: 0.2 to 0.8%, Cr: 1.90 to 7.50%, Mo: 0.40 to 1.20% is hot-processed. When manufacturing in the rolling process, it is rolled at a temperature of 750 to 1000℃ with a processing strain of 10% or more in area reduction, and then
High strength with excellent corrosion resistance and weldability, characterized by heat treatment at 700 to 800℃ for 5 to 60 minutes
Manufacturing method of Cr-Mo seamless steel pipe.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP32133387A JPH01162724A (en) | 1987-12-21 | 1987-12-21 | Manufacture of high strength cr-mo steel pipe having superior corrosion resistance and weldability |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP32133387A JPH01162724A (en) | 1987-12-21 | 1987-12-21 | Manufacture of high strength cr-mo steel pipe having superior corrosion resistance and weldability |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH01162724A JPH01162724A (en) | 1989-06-27 |
| JPH0579734B2 true JPH0579734B2 (en) | 1993-11-04 |
Family
ID=18131418
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP32133387A Granted JPH01162724A (en) | 1987-12-21 | 1987-12-21 | Manufacture of high strength cr-mo steel pipe having superior corrosion resistance and weldability |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH01162724A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4781767B2 (en) * | 2005-10-05 | 2011-09-28 | 三菱重工業株式会社 | Manufacturing method of structure for high temperature |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5629625A (en) * | 1979-08-20 | 1981-03-25 | Kawasaki Steel Corp | Manufacture of cr-mo steel hot molded product having excellent mechanical strength |
-
1987
- 1987-12-21 JP JP32133387A patent/JPH01162724A/en active Granted
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5629625A (en) * | 1979-08-20 | 1981-03-25 | Kawasaki Steel Corp | Manufacture of cr-mo steel hot molded product having excellent mechanical strength |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH01162724A (en) | 1989-06-27 |
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