JPH0261035A - Low-carbon cr-mo steel sheet excellent in welding crack resistance - Google Patents
Low-carbon cr-mo steel sheet excellent in welding crack resistanceInfo
- Publication number
- JPH0261035A JPH0261035A JP21337088A JP21337088A JPH0261035A JP H0261035 A JPH0261035 A JP H0261035A JP 21337088 A JP21337088 A JP 21337088A JP 21337088 A JP21337088 A JP 21337088A JP H0261035 A JPH0261035 A JP H0261035A
- Authority
- JP
- Japan
- Prior art keywords
- steel
- cracking
- resistance
- steel sheet
- cracking 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.)
- Granted
Links
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 75
- 239000010959 steel Substances 0.000 title claims abstract description 75
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 26
- 238000003466 welding Methods 0.000 title abstract description 9
- 238000005336 cracking Methods 0.000 claims abstract description 65
- 239000012535 impurity Substances 0.000 claims abstract description 10
- 229910052802 copper Inorganic materials 0.000 claims abstract description 9
- 229910052742 iron Inorganic materials 0.000 claims abstract description 8
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 6
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 6
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 18
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 14
- 230000003628 erosive effect Effects 0.000 abstract description 9
- 229910052796 boron Inorganic materials 0.000 abstract description 7
- 229910052804 chromium Inorganic materials 0.000 abstract description 7
- 229910052750 molybdenum Inorganic materials 0.000 abstract description 7
- 229910052759 nickel Inorganic materials 0.000 abstract description 7
- 239000000203 mixture Substances 0.000 abstract description 4
- 229910052719 titanium Inorganic materials 0.000 abstract description 4
- 238000000137 annealing Methods 0.000 abstract description 2
- 229910052710 silicon Inorganic materials 0.000 abstract 2
- 229910052782 aluminium Inorganic materials 0.000 abstract 1
- 230000000694 effects Effects 0.000 description 12
- 230000007423 decrease Effects 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 6
- 239000000126 substance Substances 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- 230000001105 regulatory effect Effects 0.000 description 4
- 239000006104 solid solution Substances 0.000 description 4
- 229910001566 austenite Inorganic materials 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000001556 precipitation Methods 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 238000010606 normalization Methods 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 238000010248 power generation Methods 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- 150000003568 thioethers Chemical class 0.000 description 2
- 229910000859 α-Fe Inorganic materials 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910052787 antimony Inorganic materials 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Landscapes
- Heat Treatment Of Steel (AREA)
- Arc Welding In General (AREA)
Abstract
Description
【発明の詳細な説明】
皮呈上東科几公国
本発明は、耐溶接割れ性に−すぐれる低炭素Ｃｒ−Ｍ
ｏ鋼板に関し、詳しくは、溶接時に生じる低温割れ及び
その後の応力除去焼鈍（以下、ＳＲという。）中に生じ
る所謂ＳＲ割れを防止した低炭素Ｃｒ−Ｍｏ鋼板に関す
る。[Detailed Description of the Invention] The present invention provides low carbon Cr-M with excellent weld cracking resistance.
Regarding o steel plates, in particular, the present invention relates to low carbon Cr-Mo steel plates that prevent low-temperature cracking that occurs during welding and so-called SR cracking that occurs during subsequent stress relief annealing (hereinafter referred to as SR).
皿来度皮惺
従来より、Ｃｒ−Ｍｏ１ｆｌ板は、石油精製をはじめと
する化学工業プラントや、発電プラントにおける中、高
温圧力容器や、タービンダイヤフラム材等の発電用ター
ビンの構造部材として広く用いられている。しかし、こ
れらの従来のＣｒ −Ｍ 。Traditionally, Cr-Mo1fl plates have been widely used as structural members of power generation turbines, such as medium and high temperature pressure vessels in oil refining and other chemical industry plants, power generation plants, and turbine diaphragm materials. ing. However, these conventional Cr-M.
鋼板は、通常、Ｃ含有量が０．１５％程度と高く、且つ
、Ｃｒ、Ｍｏ等の合金成分を多量に含有しているために
、溶接割れ感受性が高く、従って、その溶接施工にあた
っては、低温割れ防止のために、通常、１５０〜３５０
℃程度の高温の予熱を必要とし、製造期間の長期化や熱
エネルギーの大量消費等、製造コスト上昇の一因となっ
ている。Steel plates usually have a high C content of about 0.15% and contain large amounts of alloy components such as Cr and Mo, so they are highly susceptible to weld cracking. Therefore, when welding them, Usually 150 to 350 to prevent cold cracking.
It requires preheating to a high temperature of around 30°F, which is one of the causes of increased manufacturing costs, such as prolonging the manufacturing period and consuming a large amount of thermal energy.
また、他方において、Ｃｒ−Ｍｏ鋼板の溶接においては
、溶接部の残留応力の除去や、溶接硬化部の軟化等によ
る溶接継手性能の改善を目的として、溶接中或いは溶接
後にＳＲが施されることが多い。しかし、このＳＲ処理
によって、残留応力の除去又は溶接部の軟化等が行なわ
れる反面、溶接ままではみられない割れが溶接熱影響部
に発生することがある。この割れはＳＲ割れ又は再熱割
れと呼ばれており、溶接熱影響部の粗大粒域の粒界に沿
って生じることを特色としている。従って、Ｃｒ−Ｍｏ
鋼板には、耐低温割れ性と同時に耐ＳＲ割れ性を兼ね備
えることが要求される。更に、上述したＳＲ後において
、十分な強度と靭性を確保する必要があることはいうま
でもない。On the other hand, when welding Cr-Mo steel sheets, SR is applied during or after welding for the purpose of removing residual stress in the weld zone and improving weld joint performance by softening the hardened weld zone. There are many. However, although this SR treatment removes residual stress or softens the welded area, cracks that cannot be seen during welding may occur in the welded heat affected zone. This cracking is called SR cracking or reheat cracking, and is characterized by occurring along grain boundaries in the coarse grain region of the weld heat affected zone. Therefore, Cr-Mo
Steel plates are required to have both cold cracking resistance and SR cracking resistance. Furthermore, it goes without saying that it is necessary to ensure sufficient strength and toughness after the above-mentioned SR.
耐低温割れ性を高めるには、ｃｌを下げることが有効で
あることは既によく知られている。しかしｚＣ量を低減
すれば、強度の低下、耐エロージヨン性の低下、高温ク
リープ強度の低下等の問題を生じる。It is already well known that lowering Cl is effective in increasing cold cracking resistance. However, reducing the amount of zC causes problems such as a decrease in strength, a decrease in erosion resistance, and a decrease in high-temperature creep strength.
本発明者らは、Ｃｒ−Ｍｏ鋼における耐低温割れ性を改
善するために、既に、特開昭６１−１０４０５５号公報
及び特開昭６１−１０４０５６号公報に記載されている
ように、Ｃ量を著しく低減する一方、Ａ１を添加して、
適正量の５ｏｌＡｊ２を確保した後、Ｂを添加し、更に
、Ｃｕ及びＮｉを複合添加することによって、低Ｃ鋼で
ありながら、ｃｌの多い従来のＣｒ −Ｍ ｏ 鋼と比
肩し得るすぐれた強度、靭性、耐エロージヨン性、耐ク
リープ特性を有するＣ ｒ −Ｍ ｏ鋼板を得ることが
できることを見出している。In order to improve the cold cracking resistance of Cr-Mo steel, the present inventors have already determined the amount of C as described in JP-A-61-104055 and JP-A-61-104056. By adding A1, while significantly reducing
After securing an appropriate amount of 5olAj2, B is added, and furthermore, Cu and Ni are added in combination. Although it is a low C steel, it has excellent strength comparable to conventional Cr-Mo steel with a high Cl content. It has been found that it is possible to obtain a Cr-Mo steel sheet having toughness, erosion resistance, and creep resistance.
しかし、かかる低炭素Ｃｒ−Ｍｏ鋼板は、従来のＣｒ
−Ｍ ｏ鋼板に比較して、反面、ＳＲ割れ感受性が高く
、溶接施工条件によっては、ＳＲ割れが発生するおそれ
が強い。本発明者らは、このような低炭素Ｃｒ−Ｍｏ鋼
板において、耐低温割れ性及びＳＲ後のすぐれた強度靭
性を確保しつつ、その耐ＳＲ割れ性を従来のＣｒ−Ｍｏ
鋼板以上にまで高めるために鋭意研究した結果、従来の
Ｃｒ−Ｍ ｏ鋼板に比較して、前述した低炭素Ｃｒ −
Ｍ 。However, such low carbon Cr-Mo steel sheets are different from conventional Cr-Mo steel sheets.
-On the other hand, compared to Mo steel sheets, it has a higher susceptibility to SR cracking, and there is a strong possibility that SR cracking will occur depending on the welding conditions. The present inventors have found that while ensuring cold cracking resistance and excellent strength and toughness after SR in such a low carbon Cr-Mo steel sheet, the SR cracking resistance is higher than that of conventional Cr-Mo steel sheets.
As a result of intensive research to improve the Cr-Mo steel sheet to a level higher than that of steel sheets, we found that the low carbon Cr
M.
鋼板の高いＳＲ割れ感受性は、鋼中の５ｏｌＡｆに起因
し、５ｏｌＡｊ！Ｉを０．ＯＯ５％未満とすることによ
って、ＳＲ割れ感受性を従来のＣｒ−Ｍｏ鋼板と同等の
水準まで改善することができることを見出した。The high SR cracking susceptibility of steel plates is due to 5olAf in the steel, and 5olAj! I is 0. It has been found that by setting the OO to less than 5%, the SR cracking susceptibility can be improved to a level equivalent to that of conventional Cr-Mo steel sheets.
しかしながら、本発明者らが先に提案した低炭素Ｃｒ
−Ｍ ｏ鋼板において、ｓｏｌ Ａβは、焼きならし時
にＮを固定して、Ｂの焼入れ性向上効果を確保する重要
な役割を担っているため、ただ単に５ｏｌＡｊｌ！量を
規制した場合には、十分なる焼きならし効果を得ること
ができず、その結果として、所要の強度を確保、するこ
とができない。However, the low carbon Cr proposed earlier by the present inventors
- In the Mo steel sheet, sol Aβ plays an important role in fixing N during normalizing and securing the hardenability improvement effect of B, so it is simply 5olAjl! If the amount is restricted, a sufficient normalizing effect cannot be obtained, and as a result, the required strength cannot be secured.
そこで、本発明者らは、更に鋭意研究した結果、５ｏｌ
Ａｌｉｌを０．００５％未満に規制すると共に、Ｔｉを
０．００５〜ｏ、 ｏ ｓ ｏ％の範囲で添加すること
によって、すぐれた耐ＳＲ割れ性を確保し得ると同時に
、ＳＲ後においても、十分な強度を得ることができるこ
と、更に、Ｔｉと共にＣａを添加することによって、耐
ＳＲ割れ性を一層高め得ることを見出して、本発明に至
ったものである。Therefore, as a result of further intensive research, the present inventors found that 5ol
By regulating Alil to less than 0.005% and adding Ti in the range of 0.005 to 0,000%, excellent SR cracking resistance can be ensured, and at the same time, even after SR, The present invention was achieved by discovering that sufficient strength can be obtained and that SR cracking resistance can be further improved by adding Ca together with Ti.
従って、本発明は、従来のＣｒ−Ｍｏ鋼板と同等以上の
強度、靭性、耐エロージヨン性及び耐クリープ特性を有
するのみならず、耐低温割れ性及び耐ＳＲ割れ性にすぐ
れる低炭素Ｃｒ−Ｍｏ鋼板を提供することを目的とする
。Therefore, the present invention provides a low-carbon Cr-Mo steel sheet that not only has strength, toughness, erosion resistance, and creep resistance equivalent to or higher than conventional Cr-Mo steel sheets, but also has excellent cold cracking resistance and SR cracking resistance. The purpose is to provide steel plates.
」 占を ゛するための
本発明による耐溶接割れ性にすぐれる低炭素Ｃｒ −Ｍ
ｏ ｆ４板の第１は、重量％テＣ０．０３〜０．１２
％、
Ｓｔ １．００％以下、
Ｍｎ ０．２０〜０．７５％、
Ｐ ０．０２０％以下、
Ｓ ０．００９％以下、
Ｃｕ ０．０５〜０．５０％、
Ｎｉ０．０５〜０．５０％、
Ｃｒ ０．４０〜３．５０％、
Ｍｏ ０．２０−１．２５％、
Ｔｉ ０．００５〜０．０８０％、
Ｂ ０．０００３〜０．００１５％、５ｏｌＡｊ！
０．００５％未満、
残部鉄及び不可避的不純物よりなることを特徴とする。Low carbon Cr-M with excellent weld cracking resistance according to the present invention
The first of the f4 plates has a weight% TeC of 0.03 to 0.12
%, St 1.00% or less, Mn 0.20-0.75%, P 0.020% or less, S 0.009% or less, Cu 0.05-0.50%, Ni 0.05-0.50 %, Cr 0.40-3.50%, Mo 0.20-1.25%, Ti 0.005-0.080%, B 0.0003-0.0015%, 5olAj!
It is characterized by comprising less than 0.005%, the balance consisting of iron and unavoidable impurities.
本発明による耐溶接割れ性にすぐれる低炭素Ｃｒ−Ｍｏ
鋼板の第２は、上記した化学成分に加えて、
Ｃａ ０．０００５〜０．００７％
を含有し、残部鉄及び不可避的不純物よりなることを特
徴とする。Low carbon Cr-Mo with excellent weld cracking resistance according to the present invention
The second steel plate is characterized by containing 0.0005 to 0.007% of Ca in addition to the above-mentioned chemical components, with the balance consisting of iron and inevitable impurities.
尚、上記においては、５ｏｌＡｊ！量を０．００５％未
満に規制しているが、ＴｏｔａｌＡｌ！では０．００９
％未満に相当する。In addition, in the above, 5olAj! Although the amount is regulated to less than 0.005%, TotalAl! So 0.009
corresponds to less than %.
以下に本発明について詳細に説明する。The present invention will be explained in detail below.
本発明によるＣｒ−Ｍｏ鋼において、Ｂは、オーステナ
イト中に固溶し、結晶粒界に偏析して、フェライト変態
を抑制するため、鋼の焼入れ性を向上させる。しかし、
他方において、Ｂは、鋼中のＮと結合しやすい。従って
、ＢがＢＮを生成すると、鋼中におけるＢの有効量が減
少し、焼入れ性を低下させる。従って、本発明において
は、鋼の焼入れ性を向上させるべく、Ｂの有効量を確保
するために、ＴｉによってＮを固定し、更に好ましくは
、鋼中のＮ量を低減する。また、Ｂを過多に添加すると
きは、オーステナイト粒界に多量のＢ化合物が析出し、
却って焼入れ性を低下させるので、本発明においては、
Ｂは、適正量を添加することが重要である。In the Cr-Mo steel according to the present invention, B dissolves in solid solution in austenite, segregates at grain boundaries, and suppresses ferrite transformation, thereby improving the hardenability of the steel. but,
On the other hand, B easily combines with N in steel. Therefore, when B forms BN, the effective amount of B in the steel decreases, reducing the hardenability. Therefore, in the present invention, in order to improve the hardenability of the steel and ensure an effective amount of B, N is fixed with Ti, and more preferably, the amount of N in the steel is reduced. Also, when adding too much B, a large amount of B compounds precipitates at the austenite grain boundaries,
On the contrary, it reduces hardenability, so in the present invention,
It is important to add B in an appropriate amount.
しかし、本発明鋼のように、低Ｃ鋼においては、Ｂの焼
入れ性向上効果を利用するだけでは、強度、靭性ほか目
的とする望ましい特性を得ることは困難である。ここに
おいて、本発明者らは、研究を重ねた結果、低Ｃ鋼にお
いて、Ｂを適正量添加して、その焼入性向上効果を利用
すると共に、Ｃｕ及びＮｉを複合添加することにより、
鋼の焼入れ性を一層向上させると同時に、Ｂの焼入れ性
向上効果との相乗効果によって、焼ならし時のフェライ
ト析出を大幅に抑え、かくして、強度を上昇させ得ると
同時に、耐エロージヨン性及び耐クリープ特性をも従来
鋼と同等以上に改善することができることを見出したも
のである。However, in a low C steel like the steel of the present invention, it is difficult to obtain desired properties such as strength and toughness just by utilizing the hardenability improving effect of B. Here, as a result of repeated research, the present inventors have found that by adding an appropriate amount of B to low C steel and utilizing its hardenability improvement effect, and adding Cu and Ni in combination,
It further improves the hardenability of the steel, and at the same time, due to the synergistic effect with the hardenability improving effect of B, ferrite precipitation during normalization can be significantly suppressed, thus increasing the strength and improving erosion and erosion resistance. It has been discovered that the creep properties can also be improved to a level comparable to or better than that of conventional steel.
ここで、本発明において重要な因子である５ｏｌＡｆに
ついて説明する。Here, 5olAf, which is an important factor in the present invention, will be explained.
前述したように、ｓｏｌ／１７！を０．００５％未満と
することによって、耐ＳＲ割れ性を大幅に改善すること
ができる。しかし、５ｏｌＡＪは、前述したように、焼
きならし時にＮを固定して、Ｂの焼入れ性向上効果を確
保するという重要な役割を担っているため、ただ単にｓ
ｏｌ Ａβ量を低減した場合は、十分な焼きならし効果
を得ることができず、従って、所要の強度を確保するこ
とができない。As mentioned above, sol/17! By making the amount less than 0.005%, the SR cracking resistance can be significantly improved. However, as mentioned above, 5olAJ plays the important role of fixing N during normalizing and ensuring the hardenability improvement effect of B, so it is simply s
If the amount of ol Aβ is reduced, a sufficient normalizing effect cannot be obtained and, therefore, the required strength cannot be ensured.
第１図は、低炭素Ｃｒ−Ｍｏ１ｌ板における強度及びＳ
Ｒ割れ感受性に及ぼす５ｏｌＡｊｊ量の影響を示す。即
ち、
Ｃ０．０５〜０．０６％、
Ｓｉ０．０８〜０．１６％、
Ｍｎ ０．４８〜０．５０％、
Ｐ ０．００７〜０．００８％、
Ｓ ０．００３〜０．００６％、
Ｃｕ ０．１）〜０．１５％、
Ｎｉ０．１０〜０．１５％、
Ｃｒ ２．２１〜２．２５％、
Ｍｏ０．９３〜０．９５％、
Ｂ ０．０００６〜０．０００８％、及びｓｏｌ
Ａ１０．００３〜０．０４４％残部鉄及び不可避的不純
物よりなる板厚５０ｎのＣｒ −Ｍ ｏ鋼板について、
斜めＹ形溶接割れ試験片を用いたＳＲ割れ試験を行った
結果を示し、５ｏｌＡｊ！量を０．００５％未満とする
ことによって、ＳＲ割れ感受性を従来のＣｒ −Ｍ ｏ
鋼板と同等の水準まで改善することができるが、所要の
強度を確保することができないことが示される。Figure 1 shows the strength and S of a low carbon Cr-Mo1l plate.
The influence of the amount of 5olAjj on R cracking susceptibility is shown. That is, C0.05-0.06%, Si0.08-0.16%, Mn 0.48-0.50%, P 0.007-0.008%, S 0.003-0.006%, Cu 0.1) to 0.15%, Ni 0.10 to 0.15%, Cr 2.21 to 2.25%, Mo 0.93 to 0.95%, B 0.0006 to 0.0008%, and sol
A10.003~0.044% balance iron and inevitable impurities for a 50n thick Cr-Mo steel plate,
The results of an SR crack test using a diagonal Y-shaped weld crack test piece are shown, and 5olAj! By setting the amount of Cr-Mo to less than 0.005%, the SR cracking susceptibility is lower than that of conventional Cr-Mo.
Although it can be improved to the same level as steel plate, it is shown that the required strength cannot be secured.
次に、第２図は、５ｏｌＡｊ２量を０．００５％未満に
規制した低炭素Ｃｒ −Ｍ ｏ鋼板、即ち、Ｃ０．０５
〜０．０７％、
Ｓｉ０．１）〜０．２２％、
Ｍｎ ０．４５〜０．５１％、
Ｐ ０．００７〜ｏ、 ｏ ｏ ａ％、Ｓ ０
．００２〜０．０ Ｏ４％、Ｃｕ ０．１４〜０．１
６％、
Ｎｉ０．１３〜０．１６％、
Ｃｒ ２．１８〜２．２６％、
Ｍｏ０．９５〜０．９９％、
Ｂ ０．０００５〜０．０００９％、ｓｏｌ Ａｌ
２ ０．００２〜０．００４％、及びＴｉ Ｏ〜０．
１０％、
残部鉄及び不可避的不純物よりなる板厚５０鶴の低炭素
Ｃｒ −Ｍ ｏ鋼板において、強度及び耐ＳＲ割れ性に
及ぼすＴｉ１ｌの影響を調べた結果を示す。Next, FIG. 2 shows a low carbon Cr-Mo steel sheet with the amount of 5olAj2 regulated to less than 0.005%, that is, C0.05
~0.07%, Si0.1) ~0.22%, Mn 0.45~0.51%, P 0.007~o, o o a%, S 0
．． 002~0.0 O4%, Cu 0.14~0.1
6%, Ni 0.13-0.16%, Cr 2.18-2.26%, Mo 0.95-0.99%, B 0.0005-0.0009%, sol Al
2 0.002-0.004%, and TiO-0.
The results of an investigation of the influence of Ti1L on the strength and SR cracking resistance of a 50 mm thick low carbon Cr-Mo steel plate consisting of 10% iron and the balance iron and unavoidable impurities are shown below.
Ｔ３量を０．００５％以上添加することによって、Ｂの
焼入れ性向上効果を有効に活用し得て、十分な強度を確
保し得ることが理解される。更に、０゜００５％以上の
５ｏｌＡｊ！Ｉが耐ＳＲ割れ性を劣化させるのに対して
、０．０８０％までのＴｉの添加は、耐ＳＲ割れ性を向
上させることが理解される。It is understood that by adding 0.005% or more of T3, the hardenability improving effect of B can be effectively utilized and sufficient strength can be ensured. Furthermore, 5olAj of 0°005% or more! It is understood that while I deteriorates the SR cracking resistance, addition of Ti up to 0.080% improves the SR cracking resistance.
従って、Ｔｉは強力な窒化物生成元素として、５ｏＩＡ
Ｒと同様にＮを固定し得るのみならず、Ｓと結合して硫
化物を生成することによって、結晶粒界の固溶Ｓ量を低
減して、耐ＳＲ割れ特性を高めるものとみられる。Therefore, Ti is a strong nitride-forming element with 5oIA
Not only can it fix N like R, but it also combines with S to form sulfides, which reduces the amount of solid solution S at grain boundaries and seems to improve the SR cracking resistance.
しかし、Ｔｉは、ｏ、ｏａｏ％を越えて過多に添加する
ときは、Ｔｉが炭化物として結晶粒内に析出する量が増
加し、その結果として、結晶粒界と粒内の強度差を拡大
させるために、耐ＳＲ割れ性を劣化させることとなる。However, when Ti is added in excess of o, oao%, the amount of Ti precipitated within grains as carbide increases, and as a result, the difference in strength between grain boundaries and within grains increases. Therefore, the SR cracking resistance deteriorates.
従って、本発明においては、Ｔｉの添加量は、０．ＯＯ
５〜０．０８０％の範囲とする。Therefore, in the present invention, the amount of Ti added is 0. OO
The range is 5 to 0.080%.
次に、本発明によるｃｒ−Ｍｏｍにおける上記以外の化
学成分の限定理由について説明する。Next, the reasons for limiting the chemical components other than those mentioned above in cr-Mom according to the present invention will be explained.
Ｃは、鋼の強度及び耐エロージヨン性を確保するために
、本発明鋼においては、０．０３％以上を添加すること
が必要であるが、反面、Ｃｆｉの増加と共に、耐ＳＲ割
れ性のみならず、溶接性及び靭性が低下するので、添加
量の上限は０．１２％とする。In order to ensure the strength and erosion resistance of the steel, it is necessary to add 0.03% or more of C in the steel of the present invention, but on the other hand, as Cfi increases, the SR cracking resistance alone increases First, weldability and toughness deteriorate, so the upper limit of the amount added is set at 0.12%.
Ｓｉは、強度の確保及び耐酸化性の向上のために有効で
あるが、焼戻し脆化感受性を高めるので、上限は１．０
０％とする。Si is effective for ensuring strength and improving oxidation resistance, but it increases susceptibility to temper embrittlement, so the upper limit is 1.0
Set to 0%.
Ｍｎは、鋼の強度と延性を高めるのに有効であるが、過
剰に添加すると、溶接性が低下するので、添加量は０．
２０％〜０．７５％の範囲とする。Mn is effective in increasing the strength and ductility of steel, but when added in excess, weldability decreases, so the amount added is 0.
The range is 20% to 0.75%.
Ｐは、鋼中に不純物として含有されるが、靭性及び溶接
性を損なうばかりでなく、焼戻し脆化感受性及びＳＲ割
れ感受性を高めるため、低減することが望ましい。従っ
て、本発明においては、Ｐの含有量は０．０２０％以下
とする。Although P is contained as an impurity in steel, it is desirable to reduce it because it not only impairs toughness and weldability but also increases susceptibility to temper embrittlement and SR cracking. Therefore, in the present invention, the P content is set to 0.020% or less.
Ｓも鋼中に不純物として含有されるが、鋼の靭性を著し
く損ない、また、ＳＲ割れ感受性をも高めるので、低減
することが望ましく、含有量は０゜００９％以下とする
。S is also contained as an impurity in steel, but it significantly impairs the toughness of the steel and also increases the susceptibility to SR cracking, so it is desirable to reduce the S content, and the content should be 0°009% or less.
Ｃｕは、固溶強化及び析出強化に有効な成分であり、且
つ、耐エロージヨン性の向上にも効果がある。かかる効
果を有効に発揮させるためには、少なくとも０．０５％
を添加する必要がある。一方、０．５０％を越えて過剰
に添加すると、熱間加工性が劣化するので、Ｃｕの添加
量は０．０５〜０．５０％の範囲とする。Cu is an effective component for solid solution strengthening and precipitation strengthening, and is also effective for improving erosion resistance. In order to effectively exhibit this effect, at least 0.05%
need to be added. On the other hand, if added in excess of more than 0.50%, hot workability deteriorates, so the amount of Cu added is in the range of 0.05 to 0.50%.
Ｎｉは、鋼の焼入れ性を増し、また、耐エロージヨン性
の向上に効果があり、更に、高温におけるオーステナイ
ト粒界へのＣ，ｕの析出による亀甲割れを防止するのに
有効である。かかる効果を有効に発現させるためには、
０．０５％以上を添加する必要があるが、しかし、高価
な元素であるので、実用的な観点からその添加量は０．
０５〜０．５０％の範囲とする。Ni is effective in increasing the hardenability of steel and improving erosion resistance, and is also effective in preventing hexagonal cracking due to precipitation of C and u at austenite grain boundaries at high temperatures. In order to effectively express such effects,
It is necessary to add 0.05% or more, but since it is an expensive element, from a practical standpoint, the amount added is 0.05% or more.
The range is 0.05% to 0.50%.
Ｃｒは、耐酸化性、焼戻し軟化抵抗を高め、強度を確保
するのに有効であるが、過度に添加すると溶接性が劣化
する。従って、添加量は、０．４０〜３．５０％の範囲
とする。Cr is effective in increasing oxidation resistance and temper softening resistance and ensuring strength, but if excessively added, weldability deteriorates. Therefore, the amount added is in the range of 0.40 to 3.50%.
ＭＯは、鋼の焼入れ性、特にＢと共存した場合の焼なら
し時の焼入れ性を高めるのに不可欠な元素である。また
、焼戻し軟化抵抗を高め、高温強度の向上にも有効であ
って、０．２０％以上を添加する必要があるが、高価な
元素であるので、その添加量は０．２０〜１．２５％の
範囲とする。MO is an essential element for improving the hardenability of steel, especially when coexisting with B, the hardenability during normalizing. It is also effective in increasing temper softening resistance and improving high temperature strength, and it is necessary to add 0.20% or more, but since it is an expensive element, the amount added is 0.20 to 1.25%. % range.
Ｂは、前述したように、焼ならし時の焼入れ性を高め、
強度上昇に有効であるので、本発明鋼においては、０．
０００３％以上を添加することが必要である。しかし、
０．００１５％を越えて過剰に添加するときは、焼なら
し時にＢ化合物を生成し、焼入れ性を低下させると同時
に、耐ＳＲ割れ性及び靭性の劣化を伴う。従って、添加
量の上限は０゜００１５％とする。As mentioned above, B increases the hardenability during normalizing,
Since it is effective in increasing the strength, in the steel of the present invention, 0.
It is necessary to add 0,003% or more. but,
When added in excess of more than 0.0015%, a B compound is generated during normalization, which reduces hardenability and at the same time causes deterioration of SR cracking resistance and toughness. Therefore, the upper limit of the amount added is 0°0015%.
また、Ｎは、その含有量が余りに多い場合は、ＢＮを生
成しやすくなり、その結果、焼入れ性に有効なり量が減
少し、ｍｔｉの焼入れ性が低下するので、本発明鋼にお
いては、含有量は０．００７％以下とすることが好まし
い。特に好ましくは０．００５％以下である。In addition, if the content of N is too large, it becomes easy to generate BN, and as a result, the effective amount for hardenability decreases, and the hardenability of mti decreases. The amount is preferably 0.007% or less. Particularly preferably, it is 0.005% or less.
更に、Ｓｂ、Ｓｎ、Ａｓ等の不純物元素は、従来から耐
ＳＲ割れ性を劣化させることが知られている。本発明に
おいても、これら元素は、それぞれ０．０１％以下とす
ることが好ましい。Furthermore, impurity elements such as Sb, Sn, and As have been known to degrade SR cracking resistance. In the present invention, each of these elements is preferably contained in an amount of 0.01% or less.
本発明によるＣｒ−Ｍｏ鋼板は、上記した元素に加えて
、Ｃａを含有することができる。Ｃａは、結晶粒を微細
化する効果を有すると共に、硫化物を生成して、結晶粒
界における固溶Ｓ量を低減させるため、耐ＳＲ割れ性を
一層高める。この効果を有効に得るためには、０．００
０５％以上を添加することが必要であるが、過剰に添加
するときは、非金属介在物の量が増して、延性を阻害す
るので、添加量は０．００７％以下とする。The Cr-Mo steel sheet according to the present invention can contain Ca in addition to the above-mentioned elements. Ca has the effect of refining crystal grains, and also generates sulfides to reduce the amount of solid solution S at grain boundaries, thereby further increasing the SR cracking resistance. In order to effectively obtain this effect, 0.00
It is necessary to add 0.05% or more, but if added in excess, the amount of nonmetallic inclusions increases and ductility is inhibited, so the addition amount is limited to 0.007% or less.
本発明によるＣ ｒ −Ｍ ｏ鋼板を製造するには、常
法に従って製造した本発明による化学成分を有する鋼片
を熱間圧延し、その後、引続いて熱処理を行なえばよい
。In order to manufacture the Cr-Mo steel sheet according to the present invention, a steel billet having the chemical composition according to the present invention manufactured according to a conventional method is hot-rolled, and then heat-treated.
１浬Ｉじか果
以上のように、本発明によれば、低炭素Ｃｒ−Ｍｏ鋼板
において、５ｏｌＡＩ！ｉを０．００５％未満に規制す
ると共に、適正量のＴｉ及びＢとに加えて、Ｃｕ及びＮ
ｉを複合添加することによって、約０．１３〜０．１７
％のＣを含有する従来のＣｒ−Ｍｏ鋼板と比較して、す
ぐれた耐溶接割れ性を有する低炭素Ｃｒ −Ｍ ｏ Ｗ
４板を得ることができる。As described above, according to the present invention, in a low carbon Cr-Mo steel sheet, 5olAI! In addition to regulating i to less than 0.005%, in addition to appropriate amounts of Ti and B, Cu and N
By adding i in combination, about 0.13 to 0.17
Low carbon Cr-Mo W with superior weld cracking resistance compared to conventional Cr-Mo steel sheet containing % C
You can get 4 plates.
大血桝
以下に実施例を挙げて本発明を説明するが、本発明はこ
れら実施例により何ら限定されるものではない。EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples in any way.
第１表に示す化学組成を有する本発明鋼及び比較鋼の機
械的性質、耐低温割れ性及び耐ＳＲ割れ性を第２表に示
す。耐低温割れ性及び耐ＳＲ割れ特性は、板厚５０鰭の
斜めＹ形溶接割れ試験片を用いて求めたものである。Table 2 shows the mechanical properties, cold cracking resistance, and SR cracking resistance of the invention steel and comparative steel having the chemical compositions shown in Table 1. Cold cracking resistance and SR cracking resistance were determined using a diagonal Y-shaped welded cracking test piece with a plate thickness of 50 fins.
本発明鋼Ａ−Ｅ及び比較鋼Ｆ及びＧは、２．２５％Ｃｒ
−１％Ｍｏ鋼板である。本発明による鋼板Ａ−Ｅは、斜
めＹ形溶接割れ試験におけるルート割れ防止予熱温度は
１００℃以下であり、また、ＳＲ割れ率は８％以下であ
って、耐溶接割れ性にすぐれている。Inventive steels A-E and comparative steels F and G are 2.25%Cr
-1%Mo steel plate. Steel plates A-E according to the present invention have a preheating temperature for preventing root cracking of 100° C. or less in the diagonal Y-shaped weld cracking test, and an SR cracking rate of 8% or less, and have excellent weld cracking resistance.
これに対して、比較鋼Ｆは、強度、靭性及び耐低温割れ
性にはすぐれるが、５ｏｌＡｆ量を０．０３２％と多く
含有しているために、耐ＳＲ割れ性に劣る。比較鋼Ｇは
、従来より知られている高炭素２．２５％Ｃｒ−１％Ｍ
ｏ［板である。斜めＹ形溶接割れ試験におけるルート割
れ防止予熱温度は２００℃であって、低炭素鋼板に比較
して高い予熱温度を必要とする。従って、この鋼板は、
低炭素鋼板と同じ程度に予熱温度を低くして、溶接する
ことができないため、２００℃の予熱にて試験したＳＲ
割れ率が記載されている。しかし、本発明鋼板Ａ−Ｅの
ＳＲ割れ率は、この値をも下回っており、耐ＳＲ割れ性
にすぐれることが示される。On the other hand, comparative steel F has excellent strength, toughness, and cold cracking resistance, but is inferior in SR cracking resistance because it contains a large amount of 5olAf at 0.032%. Comparative steel G is the conventionally known high carbon 2.25%Cr-1%M
o[It is a board. The preheating temperature for preventing root cracking in the diagonal Y-shaped weld cracking test is 200°C, which requires a higher preheating temperature than that for low carbon steel sheets. Therefore, this steel plate is
Since it is not possible to weld at a preheating temperature as low as that of low carbon steel sheets, SR was tested at a preheating temperature of 200°C.
The cracking rate is listed. However, the SR cracking rates of the steel sheets A-E of the present invention are even lower than this value, indicating that they have excellent SR cracking resistance.
次に、本発明鋼板Ｈ及び比較鋼！及びＪは、１゜２５％
Ｃｒ−０，５％ＭＯ鋼板であるが、２．２５％Ｃｒ−１
％ＭＯ鋼板の場合と同様に、本発明鋼板Ｈは、耐低温割
れ性及び耐ＳＲ割れ性を兼備しており、比較鋼板■及び
Ｊよりも、耐溶接割れ性にすぐれている。Next, the present invention steel plate H and comparative steel! and J is 1°25%
Cr-0.5% MO steel plate, but 2.25% Cr-1
%MO steel sheet, the steel sheet H of the present invention has both cold cracking resistance and SR cracking resistance, and has better weld cracking resistance than the comparative steel sheets ① and J.
第１図は、低炭素Ｃｒ −Ｍ ｏ鋼板において、５ｏｌ
Ａ７！量と、強度及びＳＲ割れ率との関係を示すグラフ
、第２図は、５ｏｌＡｊ’ｉｌを０．ＯＯ５％未満とし
た低炭素Ｃｒ −Ｍ ｏ鋼板において、Ｔｉ量と強度及
びＳＲ割れ率との関係を示すグラフである。
第１図
７２ −ｔ （％）
第２図Figure 1 shows a low carbon Cr-Mo steel plate with 5ol
A7! Figure 2 is a graph showing the relationship between the amount, strength, and SR cracking rate. It is a graph showing the relationship between the Ti amount, strength, and SR cracking rate in a low carbon Cr-Mo steel sheet with an OO of less than 5%. Fig. 1 72 -t (%) Fig. 2
Claims (2)
溶接割れ性にすぐれる低炭素Ｃｒ−Ｍｏ鋼板。(1) C0.03-0.12% by weight, Si 1.00% or less, Mn 0.20-0.75%, P 0.020% or less, S 0.009% or less, Cu 0.05-0.50% , Ni0.05-0.50%, Cr0.40-3.50%, Mo0.20-1.25%, Ti0.005-0.080%, B0.0003-0.0015%, solAl0.005% A low carbon Cr-Mo steel sheet with excellent weld cracking resistance, characterized in that the remainder is iron and unavoidable impurities.
溶接割れ性にすぐれる低炭素Ｃｒ−Ｍｏ鋼板。(2) In weight% (a) C0.03-0.12%, Si1.00% or less, Mn0.20-0.75%, P0.020% or less, S0.009% or less, Cu0.05-0 .50%, Ni0.05-0.50%, Cr0.40-3.50%, Mo0.20-1.25%, Ti0.005-0.080%, B0.0003-0.0015%, Ca0 A low carbon Cr-Mo steel sheet with excellent weld cracking resistance, characterized by comprising: .0005 to 0.007%, solAl less than 0.005%, and the remainder iron and unavoidable impurities.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63213370A JP2583114B2 (en) | 1988-08-26 | 1988-08-26 | Low carbon Cr-Mo steel sheet with excellent weld cracking resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63213370A JP2583114B2 (en) | 1988-08-26 | 1988-08-26 | Low carbon Cr-Mo steel sheet with excellent weld cracking resistance |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0261035A true JPH0261035A (en) | 1990-03-01 |
| JP2583114B2 JP2583114B2 (en) | 1997-02-19 |
Family
ID=16638060
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP63213370A Expired - Fee Related JP2583114B2 (en) | 1988-08-26 | 1988-08-26 | Low carbon Cr-Mo steel sheet with excellent weld cracking resistance |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2583114B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1340831A1 (en) * | 2002-03-01 | 2003-09-03 | National Institute for Materials Science | Welding steel for enhancing welded joint strength |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60121228A (en) * | 1983-12-05 | 1985-06-28 | Sumitomo Metal Ind Ltd | Manufacture of tempered high tension steel plate |
| JPS61104055A (en) * | 1984-10-25 | 1986-05-22 | Kobe Steel Ltd | High-strength and high-toughness low-carbon cr-mo steel plate having excellent creep-resisting property as well as superior resistance to weld crack and erosion |
| JPS61139648A (en) * | 1984-12-11 | 1986-06-26 | Kawasaki Steel Corp | Low carbon extremely thick steel plate superior in strength and weldability |
-
1988
- 1988-08-26 JP JP63213370A patent/JP2583114B2/en not_active Expired - Fee Related
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60121228A (en) * | 1983-12-05 | 1985-06-28 | Sumitomo Metal Ind Ltd | Manufacture of tempered high tension steel plate |
| JPS61104055A (en) * | 1984-10-25 | 1986-05-22 | Kobe Steel Ltd | High-strength and high-toughness low-carbon cr-mo steel plate having excellent creep-resisting property as well as superior resistance to weld crack and erosion |
| JPS61139648A (en) * | 1984-12-11 | 1986-06-26 | Kawasaki Steel Corp | Low carbon extremely thick steel plate superior in strength and weldability |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1340831A1 (en) * | 2002-03-01 | 2003-09-03 | National Institute for Materials Science | Welding steel for enhancing welded joint strength |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2583114B2 (en) | 1997-02-19 |
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