JP2781000B2 - Method for producing high-strength steel sheet excellent in HIC resistance and SSC resistance - Google Patents
Method for producing high-strength steel sheet excellent in HIC resistance and SSC resistanceInfo
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- JP2781000B2 JP2781000B2 JP1081635A JP8163589A JP2781000B2 JP 2781000 B2 JP2781000 B2 JP 2781000B2 JP 1081635 A JP1081635 A JP 1081635A JP 8163589 A JP8163589 A JP 8163589A JP 2781000 B2 JP2781000 B2 JP 2781000B2
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Description
【発明の詳細な説明】 （産業上の利用分野） 本発明は特に耐HIC性（Hydrogen Induced Cracking）
（耐水素誘起割れ性）および耐SSC性（Sulfide Stress
Corrosion Cracking）（耐硫化物応力腐食割れ性）に優
れた引張強さ50kgkf/cm2級の高張力鋼の製造法に関する
ものである。DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is particularly applicable to HIC (Hydrogen Induced Cracking).
(Hydrogen-induced cracking resistance) and SSC resistance (Sulfide Stress)
The present invention relates to a method for producing a high-strength steel having a tensile strength of 50 kgkf / cm 2 and excellent in corrosion resistance (corrosion cracking).
（従来の技術） アンモニア・LPGなどの貯蔵タンクや石油・天然ガス
精製プラントおよび輸送用のラインパイプでは、HICや
硫化水素によるSSCが大きな問題となっている。HIC,SSC
は湿潤な硫化水素環境下の腐食反応で生じた水素による
水素脆性割れの１種と考えられている。(Conventional technology) SSC caused by HIC or hydrogen sulfide is a major problem in storage tanks for ammonia and LPG, oil and natural gas refining plants, and transportation line pipes. HIC, SSC
Is considered to be one type of hydrogen embrittlement cracking caused by hydrogen generated by a corrosion reaction in a wet hydrogen sulfide environment.
一般的なHIC対策としては、鋼の清浄度を高めること
や鋼のミクロ組織の均一化などがある。また鋼のSSC感
受性に対しては化学成分やミクロ組織、非金属介在物の
有無などによって異なるが、特に硬さの影響が大きくビ
ッカース硬さHv248（Rc22）以下ではSSCは起こらないと
されている。Common HIC measures include increasing the cleanliness of the steel and homogenizing the microstructure of the steel. The SSC susceptibility of steel depends on its chemical composition, microstructure, and the presence of non-metallic inclusions. However, it is said that the effect of hardness is particularly large and that SSC does not occur below Vickers hardness Hv248 (Rc22). .
しかし従来のHT50やHT60は比較的炭素当量の高い鋼の
焼ならし（Norma）処理あるいは特開昭59−126716号公
報で示すようにＢ添加鋼の焼入れ・焼戻し（QT）処理に
よって製造されているために、小入熱時の溶接熱影響部
（HAZ）の硬さが高く、SSC感受性が増大するという欠点
を有していた。However, conventional HT50 and HT60 are manufactured by normalizing (Norma) treatment of steel having a relatively high carbon equivalent or quenching and tempering (QT) treatment of B-added steel as disclosed in JP-A-59-126716. Therefore, the hardness of the weld heat affected zone (HAZ) during small heat input is high, and the SSC sensitivity is increased.
またＢ無添加の場合でもＣ量をはじめ添加元素や製法
法が適切でなく、母材・HAZの耐HIC性や耐SSC性は著し
く劣っていた。このため新知見に基づく画期的な高張力
鋼の開発が強く望まれていた。In addition, even when B was not added, the added elements such as the amount of C and the manufacturing method were not appropriate, and the HIC resistance and SSC resistance of the base material and HAZ were extremely poor. For this reason, the development of revolutionary high-strength steel based on new knowledge has been strongly desired.
（発明が解決しようとする課題） 本発明は耐HIC性および耐SSC性に優れた高張力鋼を安
価に製造する技術を提供するものである。(Problem to be Solved by the Invention) The present invention provides a technique for inexpensively producing high-tensile steel having excellent HIC resistance and SSC resistance.
本発明法で製造した鋼は耐HIC性に優れ、低入熱溶接
時においてもHAZ硬さを低く抑えることが可能となりき
わめて優れた耐SSC性を示す。The steel produced by the method of the present invention has excellent HIC resistance, and can suppress HAZ hardness to a low level even during low heat input welding, and exhibits extremely excellent SSC resistance.
（課題を解決するための手段） 本発明の要旨は、重量％でC:0.02〜0.06％、Si:0.6％
以下、Mn:1.0〜1.4％、P:0.010％以下、S:0.001％以
下、Al:0.001〜0.060％、Nb:0.005〜0.04％、Ti:0.005
〜0.030％、Ca:0.001〜0.006％、N:0.005％以下、必要
に応じてMo:0.05〜0.30％、Ni:0.05〜0.05％、Cu:0.05
〜0.5％、V:0.01〜0.10％の範囲内で１種または２種以
上を含有し、残部が鉄および不可避的不純物からなる鋼
を連続鋳造法によってスラブとし、再加熱なしの直送圧
延（HCR,DR）ないしはスラブ冷却後これを1100〜1250℃
の温度で再加熱してNbを溶体化し、780〜880℃の温度で
圧延を終了してただちに冷却速度５〜40℃/secで加速冷
却し、400〜550℃の温度まで水冷、その後空冷すること
を特徴とする耐HIC性および耐SSC性に優れた50kgf/cm2
級高張力鋼板の製造法にある。(Means for Solving the Problems) The gist of the present invention is as follows: C: 0.02 to 0.06% by weight, Si: 0.6%
Mn: 1.0 to 1.4%, P: 0.010% or less, S: 0.001% or less, Al: 0.001 to 0.060%, Nb: 0.005 to 0.04%, Ti: 0.005
0.030%, Ca: 0.001 to 0.006%, N: 0.005% or less, Mo: 0.05 to 0.30%, Ni: 0.05 to 0.05%, Cu: 0.05 as required
0.5%, V: 0.01 to 0.10% in the range of one or more types, the balance is made of steel consisting of iron and unavoidable impurities into a slab by continuous casting method, direct feed rolling without reheating (HCR , DR) or after slab cooling,
At the temperature of 780 to 880 ° C, finish rolling at a temperature of 780 to 880 ° C, immediately accelerate cooling at a cooling rate of 5 to 40 ° C / sec, water-cool to a temperature of 400 to 550 ° C, and then air-cool 50kgf / cm 2 with excellent HIC resistance and SSC resistance
Manufacturing method of high-grade high-strength steel sheet.
（作用） 本発明者らの研究によれば、HIC対策としては水素吸
収位置となる中心偏析の軽減や硫化物（MnS）をはじめ
とする非金属介在物の低減と、その形態制御などがきわ
めて有効であり、またSSC対策としては鋼のSSC感受性に
大きな影響を及ぼすとされるHAZ硬さを低減させること
が有効である。(Action) According to the study of the present inventors, as measures against HIC, reduction of center segregation, which is a hydrogen absorption position, reduction of nonmetallic inclusions such as sulfide (MnS), and morphological control thereof are extremely important. As an effective measure against SSC, it is effective to reduce the HAZ hardness, which is considered to have a large effect on the SSC susceptibility of steel.
HAZ硬さの低減には鋼の焼入れ性を下げることが効果
的だが、同時に母材強度をも低下させるため、両者をバ
ランスよく達成するためには鋼成分の適正化だけでは不
十分である。そこで、焼入れ性に最も顕著に効くＣおよ
びＢを極力抑えたＢフリー・低ＣをベースにHAZ硬さの
低減を図るとともに、Nb（あるいは必要に応じてＶ）添
加による析出硬化現象を圧延後直ちに加速冷却を行なう
ことによって活用し、母材強度を確保する新しい方法を
発明した。To reduce HAZ hardness, it is effective to lower the hardenability of steel, but at the same time, the base metal strength is also reduced. Therefore, optimizing the steel composition alone is not enough to achieve a balance between the two. Therefore, while reducing the HAZ hardness based on B-free and low C, which minimizes C and B, which are most remarkably effective in hardenability, the precipitation hardening phenomenon due to the addition of Nb (or V, if necessary) is performed after rolling. We have invented a new method to ensure the strength of the base metal by utilizing it by immediately performing accelerated cooling.
本発明鋼によればHICは発生せず、また実際の溶接施
工上最小入熱と想定される10kJ/cmでのMIG溶接時のHAZ
最高硬さもHv230以下に抑えることが可能となり、耐SSC
性も著しく改善された。According to the steel of the present invention, HIC does not occur, and the HAZ at the time of MIG welding at 10 kJ / cm, which is assumed to be the minimum heat input in actual welding work
The maximum hardness can be suppressed to Hv230 or less, and SSC resistance
The properties have also been significantly improved.
析出硬化は鋼中に析出物を微細に分散させることによ
ってその効果を発揮する。そのため溶鋼の凝固冷却中に
微細析出したNbの析出物が粗大化することのないよう適
切な再加熱、圧延、冷却、熱処理条件を付与する必要が
ある。Precipitation hardening exerts its effect by finely dispersing precipitates in steel. Therefore, it is necessary to provide appropriate reheating, rolling, cooling, and heat treatment conditions so that the precipitate of Nb finely precipitated during solidification and cooling of molten steel does not become coarse.
この析出硬化の活用は、圧延後ただちに加速冷却を行
なうことによって可能となったものであり、さらに400
〜550℃から空冷することにより、焼戻し処理と同等な
効果が得られるために、組織の均一化がはかられ耐硫化
水素割れ性の面からも好ましいものとなる。The use of this precipitation hardening was made possible by performing accelerated cooling immediately after rolling,
By performing air cooling from about 550 ° C., an effect equivalent to that of the tempering treatment can be obtained, so that the structure can be made uniform and the hydrogen sulfide cracking resistance is preferable.
しかし、たとえNbの析出物が鋼中に微細に分散してい
ても基本成分が適当でないと、HAZ硬さ低減と母材の高
張力化とのバランスのよい達成は困難である。However, even if the Nb precipitates are finely dispersed in the steel, it is difficult to achieve a good balance between the reduction of the HAZ hardness and the high tensile strength of the base material if the basic components are not appropriate.
以下、この点について説明する。 Hereinafter, this point will be described.
Ｃは焼入れ性に最も顕著に効くものであるが、下限0.
02％は母材および溶接部の強度確保ならびにNbなどの添
加時に、これらの効果を発揮させるための最小量であ
る。しかしＣ量が多過ぎると焼入れ性が上がり、HAZ硬
さを上昇させるため上限を0.06％とした。C has the most remarkable effect on hardenability, but has a lower limit of 0.
02% is the minimum amount for exerting these effects when securing the strength of the base metal and the weld and adding Nb and the like. However, if the C content is too large, the hardenability increases, and the upper limit is made 0.06% in order to increase the HAZ hardness.
Siは脱酸上鋼に含まれる元素であるが、多く添加する
と溶接性、HAZ靭性が劣化するため、上限を0.6％に限定
した。鋼の脱酸はAlのみでも十分可能であり、焼入れ性
の観点から0.25％以下が望ましい。Si is an element contained in the deoxidized upper steel, but if added too much, the weldability and HAZ toughness deteriorate, so the upper limit was limited to 0.6%. Steel can be sufficiently deoxidized with Al alone, and is desirably 0.25% or less from the viewpoint of hardenability.
Mnは強度、靭性を確保する上で不可欠な元素であり、
その下限は1.0％である。しかしMn量が多すぎると焼入
れ性が上昇して溶接性、HAZ靭性を劣化させるだけでな
く、スラブの中心偏析を助長するので上限を1.4％とし
た。Mn is an element indispensable for securing strength and toughness,
The lower limit is 1.0%. However, if the amount of Mn is too large, hardenability increases and not only deteriorates weldability and HAZ toughness, but also promotes center segregation of the slab, so the upper limit was made 1.4%.
Ｐは本発明鋼においては不純物であり、Ｐ量の低減は
HAZにおける粒界破壊を減少させる傾向がある。逆に多
く添加すると母材、溶接部の低温靭性を劣化させるため
上限を0.010％とした。P is an impurity in the steel of the present invention.
It tends to reduce intergranular fracture in HAZ. Conversely, if a large amount is added, the low-temperature toughness of the base metal and the welded portion is deteriorated, so the upper limit is made 0.010%.
ＳはＰと同様本発明鋼においては不純物であり、Ｓ量
の低減は粒界フェライトの生成を抑制する傾向があり、
母材および溶接部の低温靭性を向上させ、さらに介在物
としての硫化物（MnS）を低減するため0.001％以下とし
た。最も好ましいＳ量は0.0005％以下である。S is an impurity in the steel of the present invention like P, and a reduction in the amount of S tends to suppress the formation of grain boundary ferrite,
The content was made 0.001% or less in order to improve the low-temperature toughness of the base metal and the weld and further reduce the sulfide (MnS) as an inclusion. The most preferred S amount is 0.0005% or less.
Alは一般に脱酸上鋼に含まれる元素であり、最低0.00
1％の添加含有が必要である。しかし、Alが0.060％を超
えるとHAZ靭性のみならず溶接金属の靭性も著しく劣化
させるため、その上限を0.060％とした。Al is an element generally contained in the deoxidized steel and has a minimum content of 0.00
1% additive content is required. However, if Al exceeds 0.060%, not only the HAZ toughness but also the toughness of the weld metal significantly deteriorates, so the upper limit was made 0.060%.
Nbは本発明鋼において必須元素であり、焼入れ性低下
に伴う強度不足分を析出硬化として補う上で、最低0.00
5％のNb量が必要である。しかしNbは同時にHAZ硬さ上昇
も伴い、また溶接部の靭性劣化を招くため上限を0.04％
とした。Nb is an essential element in the steel of the present invention, and in order to compensate for the insufficient strength due to the decrease in hardenability as precipitation hardening, at least 0.00
A 5% Nb amount is required. However, Nb is accompanied by an increase in HAZ hardness at the same time, and also causes the toughness of the weld to deteriorate, so the upper limit is 0.04%.
And
Tiは母材およびHAZ靭性向上のために必須である。な
ぜならばTiはTiNとしてスラブ中に微細析出し、加熱時
のγ粒の粗大化を抑え圧延組織の細粒化に有効であり、
また鋼板中に存在する微細TiNは、溶接時にHAZ組織を細
粒化するためである。したがってTi量はＮ量と共に制限
されるべきものであり、Ti,N量をそれぞれ0.005％〜0.0
30％,0.005％以下に限定した。Ti is essential for improving the base metal and HAZ toughness. This is because Ti precipitates finely in the slab as TiN, which suppresses the coarsening of γ grains during heating and is effective in reducing the grain size of the rolling structure.
Further, fine TiN present in the steel sheet is for reducing the HAZ structure during welding. Therefore, the amount of Ti should be limited together with the amount of N.
Limited to 30%, 0.005% or less.
Tiの下限は母材とHAZの靭性を向上させるための必要
最小量である。一方、Ti,Nの上限はこれを超えると微細
なTiNが得られず、また過剰のTiによりTiCが析出し母材
およびHAZ靭性を劣化させるためである。The lower limit of Ti is the minimum necessary for improving the toughness of the base material and HAZ. On the other hand, the upper limits of Ti and N are beyond this, because fine TiN cannot be obtained, and TiC precipitates due to excessive Ti, deteriorating the base material and HAZ toughness.
Caは硫化物（MnS）の形態を制御し、低温靭性を向上
（シャルピー吸収エネルギーを増加）させるほか、耐水
素誘起割れ性の改善にも効果を発揮する。しかしCa量0.
001％以下では実用上効果がなく、また0.006％を超えて
添加するとCaO,CaSが多量に生成して大型介在物とな
り、鋼の靭性のみならず清浄度も害し、さらには溶接性
にも悪影響を与える。このため添加量の範囲を0.001〜
0.006％に制限した。Ca controls the form of sulfide (MnS), improves low-temperature toughness (increases Charpy absorbed energy), and has an effect on improving hydrogen-induced cracking resistance. However, the amount of Ca is 0.
If it is less than 001%, there is no practical effect, and if it exceeds 0.006%, CaO and CaS are generated in large quantities and become large inclusions, which impair not only the toughness but also the cleanliness of the steel, and also adversely affect the weldability. give. Therefore, the range of the addition amount is 0.001 to
Limited to 0.006%.
次にMo,Ni,Cu,Vを添加する理由について説明する。 Next, the reason for adding Mo, Ni, Cu, and V will be described.
基本となる成分に、さらにこれらの元素を添加する主
たる目的は、本発明鋼の優れた特徴を損なうことなく強
度、靭性など特性の向上をはかるためである。したがっ
てその添加量を自ずから制限されるべき性質のものであ
る。The main purpose of adding these elements to the basic components is to improve properties such as strength and toughness without impairing the excellent characteristics of the steel of the present invention. Therefore, the amount of addition should be naturally restricted.
Moは母材の強度、靭性をともに向上させる。しかし添
加量は多過ぎると母材、溶接部の靭性および溶接性の劣
化を招き好ましくないため上限を0.30％とした。下限は
実質的な効果が得られるための最小量とすべきで0.05％
である。これは次のNi,Cuについても同様である。Mo improves both strength and toughness of the base material. However, if the added amount is too large, the toughness and weldability of the base metal and the welded portion are deteriorated, which is not preferable. Therefore, the upper limit is set to 0.30%. The lower limit should be 0.05% for a substantial effect to be obtained
It is. This is the same for the following Ni and Cu.
Niは溶接性、HAZ靭性に悪影響を及ぼすことなく母材
の強度、靭性を向上させるが、過剰な添加は溶接性に好
ましくないため上限を0.5％とした。Ni improves the strength and toughness of the base material without adversely affecting the weldability and the HAZ toughness, but the upper limit is set to 0.5% because excessive addition is not preferable for the weldability.
CuはNiとほぼ同様の効果とともに耐食性、耐水素誘起
割れ性などにも効果があるが、過剰な添加は熱間圧延時
にCu−クラックが発生し製造困難となる。このため上限
を0.5％とした。Although Cu has almost the same effect as Ni, it also has an effect on corrosion resistance, resistance to hydrogen-induced cracking, and the like, but excessive addition causes Cu-cracks during hot rolling and makes production difficult. Therefore, the upper limit is set to 0.5%.
ＶはNbと同様析出硬化に寄与するものであるが、Nbに
比べて母材強度の強化代は小さいため0.01％未満では効
果が少なく、上限は0.10％まで許容できる。またＶはHA
Z硬さをほとんど変化させないためNbとの複合添加が望
ましい。V contributes to precipitation hardening similarly to Nb. However, since the margin for strengthening the base material is smaller than that of Nb, the effect is small at less than 0.01%, and the upper limit is allowable up to 0.10%. V is HA
In order to hardly change the Z hardness, composite addition with Nb is desirable.
鋼の成分を上記のように限定しても、製造法が適切で
なければ析出硬化を利用した母材強度の確保およびHAZ
硬さの低減を達成することはできない。このため製造条
件についても限定する必要がある。Even if the composition of steel is limited as described above, if the manufacturing method is not appropriate, securing base metal strength using precipitation hardening and HAZ
No reduction in hardness can be achieved. Therefore, it is necessary to limit the manufacturing conditions.
まず、この鋼は工業的には連続鋳造法で製造すること
が生産性およびコストの点で好ましい。スラブの再加熱
温度は1250℃以下とする必要がある。なぜなら、これ以
上の温度で再加熱すると必要以上にオーステナイト粒が
粗大化して、圧延後の組織にも影響するためである。下
限は、Nbの析出硬化を最大限に利用するため、一旦溶体
化する必要上、1100℃以上に限定した。First, it is industrially preferable to manufacture this steel by a continuous casting method in terms of productivity and cost. The reheating temperature of the slab must be 1250 ° C or less. This is because reheating at a temperature higher than this causes the austenite grains to become coarser than necessary, which also affects the structure after rolling. The lower limit is limited to 1100 ° C. or higher because it is necessary to once form a solution in order to maximize the precipitation hardening of Nb.
一旦溶体化させることにより、後工程を本発明のよう
にすることによって、Nbの析出物を微細に分散させるこ
とができ、析出硬化現象を発現させることができる。Once the solution is formed, the Nb precipitates can be finely dispersed and the precipitation hardening phenomenon can be exhibited by performing the subsequent process as in the present invention.
なお本発明においては、スラブの再加熱は必ずしも実
施する必要はなく、ホットチャージ圧延やダイレクト圧
延を行っても全く問題はない。In the present invention, it is not always necessary to reheat the slab, and there is no problem even if hot charge rolling or direct rolling is performed.
次にスラブ再加熱後の圧延・冷却条件の限定理由につ
いて述べる。Next, the reasons for limiting the rolling and cooling conditions after slab reheating will be described.
圧延終了温度が780℃未満では、MnS系介在物が残存し
た場合に延伸しやすいこと、圧延中にフェライトを加工
する危険性が生ずることなどから780℃以上でなければ
ならない。しかしあまり高温で圧延を終了した場合、圧
延により細粒化したオーステナイト粒が細び成長し、鋼
の焼入れ性が上昇するためその上限を880℃とした。ま
た圧延終了後ただちに加速冷却する理由は、従来法にし
たがい空冷した場合、空冷中にNbの析出物が粗大化して
しまい、空冷のままの強度はもとより、これを再加熱し
て焼入れ・焼戻しを行ってもその加熱時にNbが固溶しな
いため析出物を微細化できず高強度が得られない。When the rolling end temperature is lower than 780 ° C., the temperature must be 780 ° C. or higher because MnS-based inclusions are likely to be stretched when remaining, and there is a risk of processing ferrite during rolling. However, when the rolling was completed at an excessively high temperature, the austenite grains refined by rolling shrink and grow, and the hardenability of the steel increased, so the upper limit was set to 880 ° C. The reason for accelerated cooling immediately after the end of rolling is that if air cooling is performed according to the conventional method, the precipitates of Nb become coarse during air cooling. Even when the heating is performed, Nb does not form a solid solution at the time of heating, so that the precipitate cannot be refined and high strength cannot be obtained.
すなわち圧延後の加速冷却は組織の微細化をはかると
ともに析出物の粗大化を防止するためには不可欠のもの
であり、これを加速冷却完了後400〜550℃から空冷する
ことによって、焼戻し処理と同等の効果が得られ、析出
物が微細に分散すると同時に均一な微細組織となり高張
力、高靭性を確保することができる。In other words, accelerated cooling after rolling is indispensable to prevent the coarsening of precipitates as well as to refine the microstructure, and after completion of accelerated cooling, air-cooling from 400 to 550 ° C to perform tempering and The same effect is obtained, and the precipitate is finely dispersed, and at the same time, a uniform microstructure is obtained, so that high tensile strength and high toughness can be secured.
本発明は厚板ミルに適用することが最も好ましいが、
ホットコイル、形鋼などにも適用可能である。また、こ
の方法で製造した厚鋼板は圧力容器、海洋構造物、ライ
ンパイプなど厳しい環境下で使用される溶接鋼構造物に
用いることができる。The present invention is most preferably applied to a plate mill,
It is also applicable to hot coils, shaped steels, etc. Further, the steel plate manufactured by this method can be used for a welded steel structure used in a severe environment such as a pressure vessel, an offshore structure, and a line pipe.
（実 施 例） 表１は本発明を実施するにあたって使用に供した鋼の
化学成分および各々の鋼に対する製造条件（板厚は全て
25mm）、母材特性、HAZ最高硬さ、超音波探傷法により
測定したNACE環境下におけるHIC割れ面積率（CAR）とを
示したものである。(Examples) Table 1 shows the chemical components of the steels used in the practice of the present invention and the manufacturing conditions for each steel (all the thicknesses were used).
25mm), base metal properties, HAZ maximum hardness, and HIC cracking area ratio (CAR) measured in an NACE environment by ultrasonic flaw detection.
比較鋼において鋼19はＣ量が低過ぎ、また鋼21はNbが
添加されていないために強度が不足している。一方、鋼
20はＢを含有し、鋼22ではＣ量が多過ぎるためにHAZ最
高硬さを低く抑えることができていない。さらに鋼23は
Ｓ量が高く、Caが添加されていないためHICが発生して
いる。In the comparative steel, steel 19 has an excessively low C content, and steel 21 has insufficient strength because Nb is not added. Meanwhile, steel
20 contains B, and steel 22 does not have a low HAZ maximum hardness because the amount of C is too large. Further, steel 23 has a high S content, and HIC is generated because Ca is not added.
これに対して本発明法で製造した鋼板（本発明鋼）は
母材強度とHAZ最高硬さとをバランスよく達成できてい
る。その結果本発明鋼は、４点曲げのSSC試験を実降伏
応力に相当する曲げ応力を付加して行ったが、割れは全
く認められなかった。またNACE環境下におけるHIC試験
結果も良好な結果が得られた。On the other hand, the steel sheet manufactured by the method of the present invention (the steel of the present invention) achieves a good balance between base metal strength and HAZ maximum hardness. As a result, the steel of the present invention was subjected to a four-point bending SSC test by applying a bending stress corresponding to the actual yield stress, but no crack was observed. In addition, good results were obtained for the HIC test under the NACE environment.
（発明の効果） 本発明により、母材の高張力化とHAZ硬さの低減とを
同時に達成する鋼を大量かつ安価に製造することが可能
になった。その結果、硫化水素雰囲気にさらされるLPG
・ガス貯蔵用球形タンクなどの溶接鋼構造物の安全性を
大きく向上させることができた。 (Effects of the Invention) According to the present invention, it has become possible to mass-produce steel inexpensively, which achieves both high tensile strength of the base material and reduction of HAZ hardness at the same time. As a result, LPG exposed to hydrogen sulfide atmosphere
・ The safety of welded steel structures such as gas storage spherical tanks was greatly improved.
フロントページの続き (72)発明者 為広 博 千葉県君津市君津１ 新日本製鐵株式会 社君津製鐵所内 (56)参考文献 特開 昭63−38518（ＪＰ，Ａ) 特開 昭63−38519（ＪＰ，Ａ) 特開 昭63−38520（ＪＰ，Ａ) (58)調査した分野(Int.Cl.6，ＤＢ名) C21D 8/02 C22C 38/00 301Continuation of the front page (72) Inventor Hiroshi Tamehiro 1 Kimitsu, Kimitsu-shi, Chiba Prefecture Nippon Steel Corporation Kimitsu Works (56) References JP-A-63-38518 (JP, A) JP-A-63-63 38519 (JP, A) JP-A-63-38520 (JP, A) (58) Fields investigated (Int. Cl. 6 , DB name) C21D 8/02 C22C 38/00 301
Claims (2)
によってスラブとし、再加熱なしの直送圧延ないしはス
ラブ冷却後これを1100〜1250℃の温度で再加熱してNbを
溶体化し、780〜880℃の温度で圧延を終了してただちに
冷却速度５〜40℃/secで加速冷却し、400〜550℃以上の
温度まで水冷、その後空冷することを特徴とする耐HIC
性および耐SSC性に優れた50kgf/mm2級高張力鋼板の製造
法。[Claim 1] By weight%, C: 0.02 to 0.06%, Si: 0.6% or less, Mn: 1.0 to 1.4%, P: 0.010% or less, S: 0.001% or less, Al: 0.001 to 0.060%, Nb: 0.005 to 0.04%, Ti: 0.005 to 0.030%, Ca: 0.001 to 0.006%, N: 0.005% or less, The remainder is made of steel consisting of iron and unavoidable impurities, made into a slab by continuous casting, and directly rolled without reheating or After cooling the slab, it is reheated at a temperature of 1100 to 1250 ° C to solidify Nb, rolling is completed at a temperature of 780 to 880 ° C, and immediately accelerated cooling at a cooling rate of 5 to 40 ° C / sec, 400 to 550 HIC resistant, characterized by water cooling to a temperature of over ℃ and then air cooling
Manufacturing method of 50kgf / mm class 2 high-strength steel sheet with excellent heat resistance and SSC resistance.
可避的不純物からなる鋼である請求項１記載の耐HIC性
および耐SSC性に優れた50kgf/mm2級高張力鋼板の製造
法。2. The composition further contains one or more of Mo: 0.05 to 0.30%, Ni: 0.05 to 0.5%, Cu: 0.05 to 0.5%, V: 0.01 to 0.10% by weight, and the balance 2. The method for producing a 50 kgf / mm class 2 high-strength steel sheet having excellent HIC resistance and SSC resistance according to claim 1, wherein the steel comprises iron and unavoidable impurities.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1081635A JP2781000B2 (en) | 1989-04-03 | 1989-04-03 | Method for producing high-strength steel sheet excellent in HIC resistance and SSC resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1081635A JP2781000B2 (en) | 1989-04-03 | 1989-04-03 | Method for producing high-strength steel sheet excellent in HIC resistance and SSC resistance |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH02263918A JPH02263918A (en) | 1990-10-26 |
| JP2781000B2 true JP2781000B2 (en) | 1998-07-30 |
Family
ID=13751799
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1081635A Expired - Lifetime JP2781000B2 (en) | 1989-04-03 | 1989-04-03 | Method for producing high-strength steel sheet excellent in HIC resistance and SSC resistance |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2781000B2 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2967889B2 (en) * | 1991-11-12 | 1999-10-25 | 住友金属工業株式会社 | Method for producing steel with excellent fatigue crack growth characteristics in wet hydrogen sulfide environment |
| JPH0681034A (en) * | 1992-08-31 | 1994-03-22 | Sumitomo Metal Ind Ltd | Production of hot rolled steel strip for steel pipe excellent in hic resistance |
| WO2005075694A1 (en) † | 2004-02-04 | 2005-08-18 | Sumitomo Metal Industries,Ltd. | Steel product for line pipe excellent in resistance to hic and line pipe produced by using the steel product |
| RU2481415C2 (en) * | 2007-11-07 | 2013-05-10 | ДжФЕ СТИЛ КОРПОРЕЙШН | Steel sheet and steel pipe for pipelines |
| JP5900303B2 (en) * | 2011-12-09 | 2016-04-06 | Ｊｆｅスチール株式会社 | High-strength steel sheet for sour-resistant pipes with excellent material uniformity in the steel sheet and its manufacturing method |
| WO2014024234A1 (en) * | 2012-08-10 | 2014-02-13 | Nippon Steel & Sumitomo Metal Corporation | Steel plate for high strength steel pipe and high strength steel pipe |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6338519A (en) * | 1986-08-01 | 1988-02-19 | Sumitomo Metal Ind Ltd | Production of steel plate having excellent hydrogen induced cracking resistance |
| JPH0774383B2 (en) * | 1986-08-01 | 1995-08-09 | 住友金属工業株式会社 | Method for producing steel sheet with excellent resistance to hydrogen-induced cracking |
| JPS6338520A (en) * | 1986-08-01 | 1988-02-19 | Sumitomo Metal Ind Ltd | Production of steel plate having excellent hydrogen induced cracking resistance |
| JP2705946B2 (en) * | 1988-06-27 | 1998-01-28 | 新日本製鐵株式会社 | Manufacturing method of high strength steel sheet with excellent SSC resistance |
-
1989
- 1989-04-03 JP JP1081635A patent/JP2781000B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH02263918A (en) | 1990-10-26 |
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