JPS61149437A - Heat treatment of heat-resistant high-chromium ferritic steel pipe - Google Patents
Heat treatment of heat-resistant high-chromium ferritic steel pipeInfo
- Publication number
- JPS61149437A JPS61149437A JP27202984A JP27202984A JPS61149437A JP S61149437 A JPS61149437 A JP S61149437A JP 27202984 A JP27202984 A JP 27202984A JP 27202984 A JP27202984 A JP 27202984A JP S61149437 A JPS61149437 A JP S61149437A
- Authority
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- Prior art keywords
- heat
- less
- steel pipe
- steel
- cooling rate
- 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.)
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- Heat Treatment Of Articles (AREA)
Abstract
Description
【発明の詳細な説明】
〈産業上の利用分野〉
この発明は高クロムフェライト系耐熱銅管の熱処理方法
に関する。DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a heat treatment method for high chromium ferrite heat-resistant copper tubes.
〈従来技術〉
近年ボイラの蒸気条件の改善に伴い、耐熱銅管の最適材
料についての見直しが活発化しており、その中でVや鶏
を添加した9%Cr−1%MO鋼が9%CrCr−1s
銅の高温強度を改善した銅として注目されている。この
鋼により小径管から厚内の大径管まで多種類の製品がつ
くられている。<Prior art> In recent years, with the improvement of boiler steam conditions, there has been an active review of the optimal material for heat-resistant copper tubes, and among these, 9%Cr-1% MO steel with V and chicken added is 9%CrCr. -1s
It is attracting attention as a copper with improved high-temperature strength. A wide variety of products are made from this steel, from small-diameter pipes to thick, large-diameter pipes.
これら銅管においては高温強度の増加はVやNbの炭化
物を高温熱処理(焼ならし処理)により溶解させ、再析
出させることにより得ている。 ′
しかし、銅管の肉厚が厚い場合にクリープ破断強度が低
下する問題があった。In these copper tubes, the high-temperature strength is increased by dissolving carbides of V and Nb by high-temperature heat treatment (normalizing treatment) and re-precipitating them. ' However, there was a problem in that the creep rupture strength decreased when the wall thickness of the copper pipe was thick.
〈発明の概要〉
本発明は、VやNbを添加した9%Cr−1% Mo
Mのクリープ破断強度の向上を目的としてなさ扛たもの
で、加熱温度1000〜1200.750℃までの平均
冷却速度1℃/sec以上の条件で焼ならし処理を行な
い、その後室温まで冷却した後700〜800℃で焼戻
すことを特徴とするものである。<Summary of the invention> The present invention provides a 9% Cr-1% Mo
This was done for the purpose of improving the creep rupture strength of M, and after performing normalizing treatment at a heating temperature of 1000 to 1200.750°C and an average cooling rate of 1°C/sec or more, and then cooling to room temperature. It is characterized by tempering at 700 to 800°C.
本発明者らは、クリープ破断強度の低下原因につき、種
々検討を重ねた結果、高温強度の増加に寄与するNb、
Vの炭化物の挙動は焼ならし時の冷却速度に大きく影舎
を受け、厚肉の材料においては通常の空冷(放冷)処理
を行うと高温域での冷却中に炭化物が強度にあまり有効
でない形態で析出するためとの知見に至った。As a result of various studies on the causes of decrease in creep rupture strength, the present inventors found that Nb, which contributes to increase in high-temperature strength,
The behavior of carbides in V is greatly affected by the cooling rate during normalization, and when using normal air cooling (air cooling) for thick materials, carbides are not very effective in improving strength during cooling in high temperature ranges. We have come to the conclusion that this is because it precipitates in a different form.
即ち、被熱処理銅管の外径が比較的大きな場合又は肉厚
が比較的薄い場合は焼ならし時における銅管の冷却速度
は高温強度の低下が問題とならない範囲内におさまるも
のの、外径が小さく肉厚が大きくなり冷却速度がおそく
なるにつれて拡散速度の十分に大きい温度域(750℃
以上)で長く保持されることになりその後の低温時に析
出するものに比較して粗大で強度特にクリープ及びクリ
ープ破断強度の増加に対する寄与が少ない炭化物が析出
することになる。これに伴い固溶量が減少するためその
後の低温側での析出量が少くなる。In other words, if the outer diameter of the heat-treated copper tube is relatively large or the wall thickness is relatively thin, the cooling rate of the copper tube during normalizing will be within a range where the reduction in high-temperature strength will not be a problem; As the wall thickness becomes smaller and the cooling rate becomes slower, the temperature range where the diffusion rate is sufficiently large (750℃
(above)), carbides are precipitated which are coarser and contribute less to increases in strength, particularly creep and creep rupture strength, than those that precipitate at subsequent low temperatures. Along with this, the amount of solid solution decreases, so the amount of subsequent precipitation on the low temperature side decreases.
この現象は上記したように厚肉材において認められ、外
径50箇以下の銅管においては肉厚15■以上の場合に
、外径50m以上の銅管においては肉厚2(1m+以上
の場合において認められるとの知見に至ったものである
。As mentioned above, this phenomenon is observed in thick-walled materials, and in copper pipes with an outer diameter of 50 or less, the wall thickness is 15 mm or more, and in copper pipes with an outer diameter of 50 m or more, the wall thickness is 2 (in the case of 1 m+ or more). This led to the finding that it is recognized in
本発明はこの知見に基づくもので、このような寸法の銅
管の熱処理、焼ならし時においては通常の空中放冷に代
えて強制空冷、ミスト冷却、水冷等適宜の方法により7
50℃以上の高温域における冷却速度を増加させクリー
プ破断強度の向上を図ったものである。The present invention is based on this knowledge, and when heat-treating and normalizing copper pipes of such dimensions, instead of normal air cooling, appropriate methods such as forced air cooling, mist cooling, water cooling, etc. are used.
This is intended to improve creep rupture strength by increasing the cooling rate in a high temperature range of 50°C or higher.
ここでまず本発明の熱処理の対象となる鋼について述べ
ておく。本発明対象鋼はV及び励を含有する高強度鋼に
限定さn、更に詳細にいえば、C:0.04〜0.15
%、Si : 1.0%以下、Mrl:1.0%以下、
Crニア 〜12%、Mo二0.5〜1.5%、N:
0.005〜0.10 %、加えてV:0.1〜0.4
5%、Nb : 0.05〜0.60 % (7)うち
lai以上、更に必要に応じてAt:0.05%以下、
N1:0.5%以下、B:5〜looppmのうち1種
以上を含有し、残部鉄及び不可避不純物から成る鋼に限
定される。この理由は次の通りである。First, the steel to be subjected to the heat treatment of the present invention will be described. The steel targeted by the present invention is limited to high-strength steel containing V and C, more specifically, C: 0.04 to 0.15.
%, Si: 1.0% or less, Mrl: 1.0% or less,
Cr ~12%, Mo2 0.5~1.5%, N:
0.005-0.10%, plus V: 0.1-0.4
5%, Nb: 0.05-0.60% (7) Lai or more, and if necessary At: 0.05% or less,
It is limited to steel containing one or more of N1: 0.5% or less, B: 5 to looppm, and the balance consisting of iron and inevitable impurities. The reason for this is as follows.
ボイラ等の高温で使用するためには耐食性の点からCr
量は7チ以上必要である。また高温強度を確保するため
にMoは0.5%以上が必要である。cr 、 M、の
上限は靭性の確保を目的としてδ−フェライト量を40
%以下に制限するために上記値に設定する必要がある。For use at high temperatures such as boilers, Cr is used from the viewpoint of corrosion resistance.
The amount needs to be 7 inches or more. Further, in order to ensure high temperature strength, Mo needs to be at least 0.5%. The upper limit of cr, M is set by increasing the amount of δ-ferrite to 40 to ensure toughness.
It is necessary to set the above value to limit it to % or less.
V。V.
Nb量の下限は高温強度を確保するために、また上限は
こnを超えて過剰添加を行うと高温強度と靭性が劣化す
るためiこ上記のように定める。Ci−の下限は常・高
温強度を確保するため、上限は溶接性、冷間加工性を考
慮して上記値とする。N量の範囲はCと同様の理由によ
り上記値とする必要がある。Slは脱酸作用を有する有
効な元素であるが、1.0%を超えて含有させると靭性
が劣化するため上限を1.0チとする。Mnは脱酸作用
を有するとともに鋼中に存在する不純物たるSと結合し
て熱間脆性を軽減させる作用を有する。前記の作用は1
%で飽和しこれを超えて含有させても増加に伴う効果が
ないことから上限を1%とする。The lower limit of the amount of Nb is determined as above in order to ensure high temperature strength, and the upper limit is determined as above because excessive addition exceeding this amount will deteriorate high temperature strength and toughness. The lower limit of Ci- is set to ensure normal and high temperature strength, and the upper limit is set to the above value in consideration of weldability and cold workability. The range of the amount of N needs to be within the above value for the same reason as for C. Sl is an effective element that has a deoxidizing effect, but if it is contained in an amount exceeding 1.0%, toughness deteriorates, so the upper limit is set at 1.0%. Mn has a deoxidizing effect and also has the effect of reducing hot embrittlement by combining with S, which is an impurity present in steel. The above action is 1
%, and even if the content exceeds this, there is no effect associated with the increase, so the upper limit is set at 1%.
本発明が対象とする鋼は以上の元素を必須構成要件とす
るものであるが必要に応じて更にkl、B、Niの1種
又は2種以上を含有せしめても良い。Atは靭性の改善
に有効であるが、過剰に添加すると高温強度に有害であ
るためo、oss以下とする。Bは高温強度に有効であ
るが5 ppm以下では効果が少なく、l OOppm
を超えると加工性等に悪影響が出る。Niは靭性の改善
に有効な元素であるが、0.5%を超える含有は耐応力
腐食割れに悪影響があるため0.5%を上限とする。The steel targeted by the present invention has the above-mentioned elements as essential constituents, but may further contain one or more of Kl, B, and Ni, if necessary. At is effective in improving toughness, but if added in excess, it is harmful to high temperature strength, so it is set to less than o, oss. B is effective for high-temperature strength, but it is less effective below 5 ppm;
Exceeding this will have an adverse effect on workability, etc. Ni is an element effective in improving toughness, but if the content exceeds 0.5%, it has an adverse effect on stress corrosion cracking resistance, so the upper limit is set at 0.5%.
上記した組成を有する銅管の肉厚はまた外径50箇以下
の場合肉厚15露以上、外径50■以上の場合肉厚20
m以上に限定される。The wall thickness of the copper tube having the above composition is 15 cm or more if the outer diameter is 50 cm or less, and 20 cm or more if the outer diameter is 50 cm or more.
m or more.
これは上記したように、この範囲の肉厚の銅管において
クリープ破断強度の低下があるからである。This is because, as mentioned above, the creep rupture strength of a copper tube with a wall thickness within this range decreases.
以上のように限定され丸銅管に対し本発明法においては
、加熱温度1000〜1200℃、750℃までの高温
域における平均冷却速度1℃/sec以上の条件で焼な
らしを施す。In the method of the present invention, a round copper tube limited as described above is normalized at a heating temperature of 1000 to 1200°C and an average cooling rate of 1°C/sec or more in a high temperature range up to 750°C.
加熱温度を1000℃以上としたのはVや卯の炭窒化物
をマトリックス中に溶解させるためにこの温度以上とす
る必要があるためである。また1200℃をこえると結
晶粒が粗大になりすぎ、靭性が低下するためこの温度を
上限とする。The reason why the heating temperature is set to 1000° C. or higher is that it is necessary to set the heating temperature to 1000° C. or higher in order to dissolve carbonitrides of V and rabbit into the matrix. Moreover, if the temperature exceeds 1200°C, the crystal grains become too coarse and the toughness decreases, so this temperature is set as the upper limit.
次に冷却速度は750℃までの高温域においては炭化物
の分布に大きな影響を与えるため上述したように一定の
速度以上で冷却する必要がある。Next, as for the cooling rate, in a high temperature range up to 750° C., the distribution of carbides is greatly affected, so as mentioned above, it is necessary to cool at a certain rate or higher.
第1図に1050℃から750℃までの冷却速度とクリ
ープ破断時間との関係を示す。図中各プロットの番号は
後記する第1表の鋼種番号であり、成分系にわけて表示
しである。FIG. 1 shows the relationship between the cooling rate and creep rupture time from 1050°C to 750°C. The numbers in each plot in the figure are the steel type numbers in Table 1, which will be described later, and are divided into component systems.
このグラフかられかるように冷却速度が大きいほど高温
強度が上昇し、1℃/sec以上・望ましくは3℃/s
ec以上とするのが良いことがわかる。したがって本発
明では750℃までの平均冷却速度を1 ℃/sec以
上と限定する。As can be seen from this graph, the higher the cooling rate, the higher the high temperature strength.
It can be seen that it is better to set it to ec or higher. Therefore, in the present invention, the average cooling rate up to 750°C is limited to 1°C/sec or more.
なお鋼16は鋼11−鋼15のラインにのっていないが
、これは靭性をより重視した熱処理を行っているためで
ある。Note that Steel 16 is not on the line of Steel 11-Steel 15, but this is because the heat treatment is performed with more emphasis on toughness.
750℃より低温での冷却速度は材料の特性には大きな
影響を与えないが厚肉の製品においては割れの発生しな
い程度に特に400℃以下の冷却速度を21:/sec
以下とする必要がある。The cooling rate at temperatures lower than 750°C does not have a major effect on the properties of the material, but for thick-walled products, the cooling rate at temperatures below 400°C should be set at 21:/sec to prevent cracking.
It is necessary to do the following.
その後室温まで冷却し九後700〜800℃で焼戻しを
行なう。700℃未満で焼戻し処理を行なうと常温強度
が高くなり加工性が悪くなるためである。又SOO℃を
超えて行うとオースブナイトが形成される危険性があり
意味がなくなることから上限を800℃とする。Thereafter, it is cooled to room temperature and then tempered at 700 to 800°C. This is because if the tempering treatment is performed at a temperature lower than 700°C, the room temperature strength will increase and the workability will deteriorate. Furthermore, if the temperature exceeds SOO°C, there is a risk of ausbunite being formed and there is no meaning, so the upper limit is set at 800°C.
又焼もどし時間は所期の焼もどし効果を得るためには3
0分以上が必要である。In addition, the tempering time should be 3 to obtain the desired tempering effect.
0 minutes or more is required.
〈実施例〉
第1表にその組成と寸法を示した銅管及び鋼板を夫々第
2表に示す条件で規準−焼戻処理を行った。得られ次鋼
材の650℃負荷llk/−におけるクリープ破断時間
を第2表右端に示す。規準時に通常の放冷を行った鋼1
.4.9.11,14.20は750℃までの高温域の
平均冷却速度が1℃/sec未満になっており、650
℃におけるクリープ破断時間も芳しくない。<Example> Copper tubes and steel plates whose compositions and dimensions are shown in Table 1 were subjected to standard-tempering treatment under the conditions shown in Table 2. The creep rupture time of the obtained steel materials under a load of 650° C. is shown on the right side of Table 2. Steel 1 subjected to normal cooling during standardization
.. For 4.9.11 and 14.20, the average cooling rate in the high temperature range up to 750°C is less than 1°C/sec, and 650
The creep rupture time at ℃ is also not good.
こnに対し強制空冷、水冷等を行って当該高温域での平
均冷却速度を1℃/sec以上とした場合はその冷却速
度が大になるにつれてクリープ破断時間が長くなってい
ることがわかる。On the other hand, when forced air cooling, water cooling, etc. are performed to increase the average cooling rate in the high temperature range to 1° C./sec or more, it can be seen that the creep rupture time increases as the cooling rate increases.
これにより本発明法の効果が確認され7t。This confirmed the effectiveness of the method of the present invention and resulted in 7 tons.
第1図は平均冷却速度とクリープ破断時間との関係を示
すグラフである。FIG. 1 is a graph showing the relationship between average cooling rate and creep rupture time.
Claims (1)
:1.0%以下、Cr:7〜12%、Mo:0.5〜1
.5%、N:0.005〜0.10%、加えてV:0.
1〜0.45%、Nb:0.05〜0.60%のうち1
種以上、更に必要に応じてAl:0.05%以下、Ni
:0.5%以下、B:5〜100ppmのうち1種以上
を含有し、残部鉄及び不可避不純物から成 り、 外径50mm以下、肉厚15mm以上又は外径50mm
以上、肉厚20mm以上の銅管を熱処理する方法におい
て、 加熱温度1000〜1200°、750℃までの平均冷
却速度1℃/sec以上の条件で焼ならし処理を行ない
、その後室温まで冷却した後 700〜800℃で焼戻すことを特徴とする高クロムフ
ェライト系耐熱銅管の熱処理方法。[Claims] C: 0.04 to 0.15%, Si: 1.0% or less, Mn
: 1.0% or less, Cr: 7-12%, Mo: 0.5-1
.. 5%, N: 0.005-0.10%, and V: 0.
1 to 0.45%, Nb: 1 out of 0.05 to 0.60%
species or more, and if necessary Al: 0.05% or less, Ni
: 0.5% or less, B: Contains one or more of 5 to 100 ppm, the balance consists of iron and unavoidable impurities, and has an outer diameter of 50 mm or less, a wall thickness of 15 mm or more, or an outer diameter of 50 mm.
As described above, in the method of heat treating a copper tube with a wall thickness of 20 mm or more, normalizing treatment is performed under the conditions of a heating temperature of 1000 to 1200° and an average cooling rate of 1°C/sec or more to 750°C, and then cooling to room temperature. A heat treatment method for a high chromium ferrite heat-resistant copper tube, which is characterized by tempering at 700 to 800°C.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP27202984A JPS61149437A (en) | 1984-12-25 | 1984-12-25 | Heat treatment of heat-resistant high-chromium ferritic steel pipe |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP27202984A JPS61149437A (en) | 1984-12-25 | 1984-12-25 | Heat treatment of heat-resistant high-chromium ferritic steel pipe |
Publications (1)
Publication Number | Publication Date |
---|---|
JPS61149437A true JPS61149437A (en) | 1986-07-08 |
Family
ID=17508131
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP27202984A Pending JPS61149437A (en) | 1984-12-25 | 1984-12-25 | Heat treatment of heat-resistant high-chromium ferritic steel pipe |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPS61149437A (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS62103344A (en) * | 1985-07-25 | 1987-05-13 | Nippon Kokan Kk <Nkk> | Nine percent chromium heat-resisting steel reduced in sensitivity to low-and high-temperature cracking, excellent in toughness, and having high creep strength at welded joint |
JPS63210233A (en) * | 1987-02-25 | 1988-08-31 | Sumitomo Metal Ind Ltd | Manufacture of high-cr ferritic-steel product excellent in strength at high temperature |
JPS6442528A (en) * | 1987-08-11 | 1989-02-14 | Sumitomo Metal Ind | Heat treating method for high cr ferritic welded steel pipe |
JP2006348385A (en) * | 2006-06-28 | 2006-12-28 | National Institute For Materials Science | Mx carbonitride precipitation-strengthened heat-resistant steel |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5481116A (en) * | 1977-12-12 | 1979-06-28 | Kawasaki Steel Co | Ferritic chromiummmolybdenum steel |
JPS5696056A (en) * | 1979-12-28 | 1981-08-03 | Mitsubishi Heavy Ind Ltd | High chromium steel for high temperature use |
JPS59140352A (en) * | 1983-01-28 | 1984-08-11 | Nippon Kokan Kk <Nkk> | Heat-resistant high-chromium steel with superior toughness |
-
1984
- 1984-12-25 JP JP27202984A patent/JPS61149437A/en active Pending
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5481116A (en) * | 1977-12-12 | 1979-06-28 | Kawasaki Steel Co | Ferritic chromiummmolybdenum steel |
JPS5696056A (en) * | 1979-12-28 | 1981-08-03 | Mitsubishi Heavy Ind Ltd | High chromium steel for high temperature use |
JPS59140352A (en) * | 1983-01-28 | 1984-08-11 | Nippon Kokan Kk <Nkk> | Heat-resistant high-chromium steel with superior toughness |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS62103344A (en) * | 1985-07-25 | 1987-05-13 | Nippon Kokan Kk <Nkk> | Nine percent chromium heat-resisting steel reduced in sensitivity to low-and high-temperature cracking, excellent in toughness, and having high creep strength at welded joint |
JPS63210233A (en) * | 1987-02-25 | 1988-08-31 | Sumitomo Metal Ind Ltd | Manufacture of high-cr ferritic-steel product excellent in strength at high temperature |
JPS6442528A (en) * | 1987-08-11 | 1989-02-14 | Sumitomo Metal Ind | Heat treating method for high cr ferritic welded steel pipe |
JP2006348385A (en) * | 2006-06-28 | 2006-12-28 | National Institute For Materials Science | Mx carbonitride precipitation-strengthened heat-resistant steel |
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