JP3153071B2 - High-strength steel rod excellent in delayed fracture resistance and method of manufacturing the same - Google Patents
High-strength steel rod excellent in delayed fracture resistance and method of manufacturing the sameInfo
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- JP3153071B2 JP3153071B2 JP11194194A JP11194194A JP3153071B2 JP 3153071 B2 JP3153071 B2 JP 3153071B2 JP 11194194 A JP11194194 A JP 11194194A JP 11194194 A JP11194194 A JP 11194194A JP 3153071 B2 JP3153071 B2 JP 3153071B2
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- delayed fracture
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- steel rod
- fracture resistance
- strength
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Description
【0001】[0001]
【産業上の利用分野】本発明は耐遅れ破壊特性に優れた
高強度鋼棒およびその製造方法に関するものである。具
体的にはJIS G 3109 D種 1号 SBPD
130/145相当のPC鋼棒の耐遅れ破壊特性の改
善に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength steel rod excellent in delayed fracture resistance and a method for producing the same. Specifically, JIS G 3109 D class 1 No. SBPD
It relates to improvement of delayed fracture resistance of PC steel rod equivalent to 130/145.
【0002】[0002]
【従来の技術】PCパイルにはパイルのひび割れ防止、
曲げ強さ確保のため、PC鋼棒が補強材として用いられ
る。PCパイルの製造工程においてはまず、PC鋼棒に
よって鉄筋籠を形成し、このPC鋼棒に引張強さの70
%の引張応力を負荷し、この籠を型枠内に配置し、コン
クリート原料を型枠内に投入し、遠心成形することによ
って製造される。ここにおいて、引張応力を負荷された
PC鋼棒はコンクリートに圧縮応力を与えることによっ
て、コンクリートのひび割れを防ぐ作用を持つ。PC鋼
棒は強度が145kgf/mm2 以上と高いうえに、コ
ンクリート中で強度の70%の張力を負荷された状態で
使用されるため、遅れ破壊が発生する可能性が高い。こ
のため、耐遅れ破壊特性の優れた鋼棒が必要となる。2. Description of the Related Art Prevention of pile cracks in PC piles,
PC steel bars are used as reinforcements to ensure bending strength. In the manufacturing process of the PC pile, first, a reinforcing rod cage is formed by using a PC steel rod, and the PC steel rod has a tensile strength of 70%.
% Tensile stress is applied, the basket is placed in a mold, the concrete raw material is put in the mold, and the basket is manufactured by centrifugal molding. Here, the PC steel bar to which the tensile stress is applied has an action of preventing the concrete from cracking by applying a compressive stress to the concrete. Since the PC steel bar has a high strength of 145 kgf / mm 2 or more and is used in a state where a tension of 70% of the strength is applied in the concrete, delayed fracture is highly likely to occur. For this reason, a steel rod having excellent delayed fracture resistance is required.
【0003】遅れ破壊は粒界破壊が支配的であるため、
旧オーステナイト粒を微細化する対策(特開平5−17
1356号公報)や、焼戻し温度を高くする対策(特開
平5−117811号公報)等が取られている。また、
遅れ破壊の原因となる水素の侵入を抑制するため、合金
元素の添加により耐腐食特性を向上させることも試みら
れている(特開平2−240236号公報、特開平2−
240237号公報、特開平2−240244号公
報)。更に合金元素の添加による高温焼戻しが耐遅れ破
壊特性を向上させるという提案もある。[0003] In the delayed fracture, grain boundary fracture is dominant.
Countermeasures for refining old austenite grains (JP-A-5-17
No. 1356) and measures to increase the tempering temperature (Japanese Patent Laid-Open No. 5-117811). Also,
In order to suppress the intrusion of hydrogen that causes delayed fracture, attempts have been made to improve the corrosion resistance by adding an alloying element (JP-A-2-240236 and JP-A-2-240236).
240237, JP-A-2-240244). Further, there is a proposal that high-temperature tempering by adding an alloy element improves delayed fracture resistance.
【0004】[0004]
【発明が解決しようとする課題】しかしながら、上記い
ずれの方法も遅れ破壊の特徴である粒界破壊の抑制は不
十分で、耐遅れ破壊特性向上には完全とは言えない。そ
こで本発明は上記のような事情に着目してなされたもの
であって、その目的は粒界炭化物のサイズを制御するこ
とによって遅れ破壊感受性が低い高強度棒鋼を提供しよ
うとするものである。However, none of the above-mentioned methods sufficiently suppresses grain boundary fracture, which is a feature of delayed fracture, and cannot be said to be perfect for improving delayed fracture resistance. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a high-strength steel bar having low delayed fracture susceptibility by controlling the size of grain boundary carbide.
【0005】[0005]
【課題を解決するための手段】本発明者らは、高強度鋼
材の遅れ破壊現象をシミュレーションでき、しかも遅れ
破壊特性を破壊に要する水素量で評価できる遅れ破壊試
験法を開発した。この方法を用いた試験結果から、棒鋼
の熱処理における焼戻しの際の加熱速度と保持温度、保
持時間の制御により遅れ破壊に要する水素量を増加でき
る、つまり耐遅れ破壊特性を改善できるとの知見を得
て、本発明を完成するに至ったものである。Means for Solving the Problems The present inventors have developed a delayed fracture test method which can simulate the delayed fracture phenomenon of a high-strength steel material and can evaluate the delayed fracture characteristic with the amount of hydrogen required for fracture. From the test results using this method, it was found that the amount of hydrogen required for delayed fracture can be increased by controlling the heating rate, holding temperature, and holding time during tempering in heat treatment of steel bars, that is, delayed fracture resistance can be improved. As a result, the present invention has been completed.
【0006】その要旨とするところは、C:0.15〜
0.50%、Si:0.1〜2.0%、Mn:0.05
〜2.0%、P:0.015%以下、S:0.02%以
下、Al:0.005〜0.1%を含有し、さらに必要
に応じCr:0.1〜3.0%、Mo:0.05〜1.
2%、Ni:0.05〜2.0%、V:0.10〜0.
50%、Ti:0.005〜0.10%、Nb:0.0
05〜0.10%のうち1種または2種以上を含有し、
残部がFeおよび不可避的不純物よりなる鋼で、焼戻し
マルテンサイト組織からなり、JIS G 0551に
よる旧オーステナイト粒度番号が10以上であるととも
に旧オーステナイト粒界の炭化物のサイズが0.2μm
以下であり、且つ強度が145kgf/mm2 以上であ
ることを特徴とする耐遅れ破壊特性に優れた高強度鋼棒
であり、さらに上記成分の鋼を熱間圧延して焼き入れ後
直ちに350℃〜500℃の温度範囲に50℃/sec
以上の加熱速度で昇温し、10〜50秒保持して焼戻
し、JIS G 0551による旧オーステナイト粒度
番号が10以上であるとともに旧オーステナイト粒界の
炭化物のサイズが0.2μm以下であり、且つ強度が1
45kgf/mm 2 以上である焼戻しマルテンサイト組
織からなる鋼棒を得ることを特徴とする耐遅れ破壊特性
に優れた高強度鋼棒の製造方法である。[0006] The summary is that C: 0.15
0.50%, Si: 0.1 to 2.0%, Mn: 0.05
2.0%, P: 0.015% or less, S: 0.02% or less, Al: 0.005 to 0.1%, and Cr: 0.1 to 3.0% as required. , Mo: 0.05-1.
2%, Ni: 0.05-2.0%, V: 0.10-0.
50%, Ti: 0.005 to 0.10%, Nb: 0.0
Containing one or more of 0.05 to 0.10%,
The balance is steel consisting of Fe and unavoidable impurities, has a tempered martensite structure, has a prior austenite grain size number of 10 or more according to JIS G 0551, and has a carbide size of 0.2 μm in the prior austenite grain boundary.
A high-strength steel rod excellent in delayed fracture resistance, characterized by having a strength of not less than 145 kgf / mm 2 , and a steel of the above-mentioned composition being hot-rolled and immediately heated to 350 ° C. 50 ° C / sec in a temperature range of ~ 500 ° C
The temperature was raised at the above heating rate, tempered by holding for 10 to 50 seconds, and the prior austenite grain size according to JIS G 0551.
Number 10 or more and the former austenite grain boundary
The size of the carbide is 0.2 μm or less and the strength is 1
Tempered martensite set with 45 kgf / mm 2 or more
This is a method for producing a high-strength steel rod excellent in delayed fracture resistance, characterized by obtaining a steel rod made of a woven material .
【0007】[0007]
【作用】この遅れ破壊試験方法は図1の形状の環状ノッ
チをもつPC鋼棒からなる供試材に定電流陰極チャージ
によって水素をチャージした後、大気中で図2で示され
るカンチレバー式の試験機によって引張強度の70%の
定荷重引張応力を負荷し、破断に要する時間を測定する
ものである。他方、これと同一形状の供試材に同一条件
で陰極チャージを行い、この供試材にチャージされた水
素量をガスクロマトグラフ法により測定する。このと
き、100℃/hourの昇温速度で加熱し測定を行う
が、水素の放出プロファイルには図3のように2つのピ
ークが現れる。このうちの低温側のピークは室温で拡散
し得る水素量を示すため、これを拡散性水素量と定義す
る。This delayed fracture test method is based on the cantilever type test shown in FIG. 2 after charging hydrogen to a test material consisting of a PC steel rod having an annular notch in the shape of FIG. A constant load tensile stress of 70% of the tensile strength is applied by a machine, and the time required for breaking is measured. On the other hand, a cathode material is charged under the same conditions to a specimen having the same shape, and the amount of hydrogen charged to the specimen is measured by gas chromatography. At this time, the measurement is performed by heating at a heating rate of 100 ° C./hour, and two peaks appear in the hydrogen release profile as shown in FIG. Since the peak on the low temperature side shows the amount of hydrogen that can diffuse at room temperature, this is defined as the amount of diffusible hydrogen.
【0008】こうして求めた破断時間とそのときの拡散
性水素量をグラフ化すると図4の様になる。この図から
負荷後100時間たっても破断しない水素量Hcを求
め、これを限界拡散性水素量と定義し、この大小で鋼材
の耐遅れ破壊特性を判断する。この遅れ破壊試験方法に
よってPC鋼棒での遅れ破壊クラックの発生と伝播現象
を調査した結果、次のことが判明した。すなわち、鋼を
通常の熱間圧延をした後、水冷することによってマルテ
ンサイト組織にした後、50℃/sec以上、好ましく
は100℃/sec以上の加熱速度で昇温し、350℃
〜500℃の温度範囲に10秒〜50秒、好ましくは1
0〜20秒の時間保持して焼戻すことにより、旧オース
テナイト粒界上に析出する炭化物が成長するに十分な時
間がないため、普通の焼戻しで粒界炭化物サイズは0.
4μm程度であるのに対して、0.2μm以下、前記の
好ましい条件下では0.1μm以下という微少な粒界炭
化物をもつ焼戻しマルテンサイト組織を得る。このよう
な微細な粒界炭化物を特徴とする組織を持つ鋼では、亀
裂が旧オーステナイト粒界に沿って伝播することが困難
であり、したがって粒界破壊するに際し多量の拡散性水
素を必要とする、すなわち、耐遅れ破壊特性が大幅に改
善できることを見出したのである。FIG. 4 shows a graph of the rupture time thus obtained and the amount of diffusible hydrogen at that time. From this figure, the amount of hydrogen Hc that does not break even after 100 hours from the loading is determined, and this is defined as the critical diffusible hydrogen amount, and the delayed fracture resistance of the steel material is determined based on the magnitude of the critical amount of hydrogen. As a result of investigating the occurrence and propagation of delayed fracture cracks in PC steel rods using this delayed fracture test method, the following was found. That is, the steel is subjected to normal hot rolling, and then water-cooled to form a martensite structure, and then heated at a heating rate of 50 ° C / sec or more, preferably 100 ° C / sec or more, to 350 ° C.
10 to 50 seconds, preferably 1 to 500 ° C.
Tempering while holding for a time of 0 to 20 seconds does not have enough time for the carbide to precipitate on the prior austenite grain boundaries, so that the grain size of the grain boundary carbides is 0.1 mm by ordinary tempering.
A tempered martensitic structure having fine grain boundary carbides of about 4 μm or less and 0.2 μm or less and 0.1 μm or less under the above preferable conditions is obtained. In steels with a structure characterized by such fine grain boundary carbides, it is difficult for the crack to propagate along the old austenite grain boundaries, and thus requires a large amount of diffusible hydrogen for grain boundary fracture. That is, they have found that the delayed fracture resistance can be greatly improved.
【0009】これらの実験及び検討の結果本発明を完成
したものであって、本発明に従う高強度鋼棒の合金成分
の範囲は次の理由で決定される。Cは、焼入れ、焼戻し
により高強度を得るためには0.15%以上必要である
が、0.5%を超えると靱性を劣化させるとともに耐遅
れ破壊特性も劣化させる元素であるために0.15%以
上0.50%以下とした。Siは鋼の脱酸および強度を
高めるのに必要な元素であり、0.1%以上添加する。
2.0%を超えると脆化の原因となるので、0.1%以
上2.0%以下とした。Mnは鋼の脱酸および焼入れ性
の確保のため0.05%以上必要であり、2.0%を超
えるとオーステナイト域加熱時に粒界に偏析し粒界を脆
化させるとともに耐遅れ破壊特性を劣化させる元素であ
るために0.05%以上2.0%以下とした。As a result of these experiments and studies, the present invention has been completed, and the range of the alloy composition of the high-strength steel rod according to the present invention is determined for the following reasons. C is required to be 0.15% or more in order to obtain high strength by quenching and tempering, but if it exceeds 0.5%, it is an element that deteriorates toughness and delayed fracture resistance. 15% or more and 0.50% or less. Si is an element necessary for increasing deoxidation and strength of steel, and is added in an amount of 0.1% or more.
If it exceeds 2.0%, it will cause embrittlement, so it was made 0.1% or more and 2.0% or less. Mn is required to be 0.05% or more in order to ensure the deoxidation and hardenability of steel. If it exceeds 2.0%, Mn segregates at the grain boundary during heating in the austenite region, embrittles the grain boundary, and has a delayed fracture resistance. Since it is an element that deteriorates, the content is set to 0.05% or more and 2.0% or less.
【0010】Pは焼入れ性元素としては有効であるが、
凝固時にミクロ偏析し、さらにオーステナイト域加熱時
に粒界に偏析し粒界を脆化させるとともに耐遅れ破壊特
性を劣化させる元素であるために0.015%以下とし
た。Sは不可避的不純物であるが、オーステナイト域加
熱時に粒界に偏析し粒界を脆化させるとともに耐遅れ破
壊特性を劣化させる元素であるために0.02%以下と
した。Alは鋼の脱酸に有効な元素であるために0.0
05%以上必要であるが、0.1%を超えると靱性の劣
化を招くために0.005%以上0.1%以下とした。P is effective as a hardenable element,
Since the element segregates microscopically during solidification and segregates at the grain boundary during heating in the austenite region, embrittles the grain boundary and deteriorates delayed fracture resistance, the content is 0.015% or less. Although S is an unavoidable impurity, it is segregated at the grain boundary during heating in the austenite region, embrittles the grain boundary, and deteriorates the delayed fracture resistance, so that the content of S is set to 0.02% or less. Al is an effective element for deoxidizing steel, so
It is required to be at least 05%, but if it exceeds 0.1%, toughness is deteriorated.
【0011】また、耐遅れ破壊特性に及ぼす合金元素、
焼戻し温度の影響を調べたところ、従来の高強度棒鋼に
比べて、Cr、Mo、Ni、V、Ti、Nbの添加が有
効であることを見出した。従って、必要に応じこれらの
元素の内、1種または2種以上を含有させる。[0011] Further, an alloying element affecting the delayed fracture resistance,
Examination of the effect of the tempering temperature revealed that the addition of Cr, Mo, Ni, V, Ti, and Nb was more effective than conventional high-strength steel bars. Therefore, one or more of these elements may be contained as necessary.
【0012】Crは鋼の焼入れ性を得るためには0.1
%以上必要であるが、多すぎると靱性の劣化、冷間加工
性の劣化を招く元素であるために3.0%以下とした。
Moは鋼の焼入れ性を得るために、また焼戻し軟化抵抗
を有し400℃以上の焼戻し温度で安定して145kg
f/mm2 以上の引張荷重を得るのに0.05%以上必
要な元素であり、1.2%を超えるとその効果は飽和し
コストの上昇を招くために0.05%以上1.2%以下
とした。Niは靱性を向上させるとともに耐遅れ破壊特
性を向上させるために0.05%以上必要であるが、
2.0%を超えるとその効果は飽和しむしろコスト上昇
を招くために0.05%以上2.0%以下とした。[0012] In order to obtain the hardenability of steel, Cr is 0.1%.
% Is necessary, but if it is too large, it is an element that causes deterioration of toughness and cold workability, so that the content was made 3.0% or less.
Mo has a tempering softening resistance to obtain the hardenability of steel, and has a stable temperature of 145 kg at a tempering temperature of 400 ° C. or more.
It is an element necessary for 0.05% or more to obtain a tensile load of f / mm 2 or more. If it exceeds 1.2%, its effect is saturated and the cost is increased. % Or less. Ni is required to be 0.05% or more to improve toughness and delayed fracture resistance.
If it exceeds 2.0%, the effect is not saturated but rather increases the cost.
【0013】V、Ti、Nbは、結晶粒の微細化に寄与
し、かつ水素との親和性に富み鋼中での水素の拡散・集
積を抑制することにより耐遅れ破壊特性向上に有効な元
素であるため、それぞれV:0.10%以上、Ti:
0.005%以上、Nb:0.005%以上必要であ
る。ただし多すぎるとその効果は飽和しむしろ靱性を劣
化させる元素であるためにそれぞれV:0.50%以
下、Ti:0.10%以下、Nb:0.10%以下とし
た。V, Ti, and Nb are elements that contribute to the refinement of crystal grains and have a high affinity for hydrogen and are effective in improving delayed fracture resistance by suppressing the diffusion and accumulation of hydrogen in steel. Therefore, V: 0.10% or more and Ti:
0.005% or more, Nb: 0.005% or more is required. However, if the content is too large, the effect saturates and the element is rather deteriorated in toughness. Therefore, V: 0.50% or less, Ti: 0.10% or less, and Nb: 0.10% or less, respectively.
【0014】旧オーステナイト粒度は、JIS G 0
551による粒度番号が10以上の微細粒では限界拡散
性水素量が多く、遅れ破壊特性が向上する。粒度番号が
10未満になると限界拡散性水素量は少なく、遅れ破壊
特性が悪化するため、粒度番号を10以上とした。次に
本発明で目的とする高強度PC鋼棒の遅れ破壊特性の向
上に対して最も重要な点である粒界炭化物のサイズの限
定理由について述べる。図5に焼戻しマルテンサイト組
織からなるPC鋼棒の限界拡散性水素量に及ぼす粒界炭
化物サイズの影響について解析した一例を示す。粒界炭
化物サイズが0.2μm以上では限界拡散性水素量の向
上効果が少ない、即ち遅れ破壊特性向上効果が少ないた
め、粒界炭化物サイズを0.2μm以下に限定した。The prior austenite grain size is JIS G 0
Fine particles having a particle size number of 10 or more according to 551 have a large critical diffusible hydrogen content, and the delayed fracture characteristics are improved. When the particle size number is less than 10, the critical diffusible hydrogen amount is small and the delayed fracture characteristics deteriorate, so the particle size number is set to 10 or more. Next, the reason for limiting the size of the grain boundary carbide, which is the most important point for the improvement of the delayed fracture characteristics of the high-strength PC steel rod intended in the present invention, will be described. FIG. 5 shows an example in which the effect of the grain boundary carbide size on the critical diffusible hydrogen content of a PC steel rod having a tempered martensite structure is analyzed. If the grain boundary carbide size is 0.2 μm or more, the effect of improving the critical diffusible hydrogen amount is small, that is, the effect of improving the delayed fracture characteristics is small, so the grain boundary carbide size is limited to 0.2 μm or less.
【0015】本発明の高強度PC鋼棒の製造方法では、
通常の熱間圧延を行った後直ちに焼入れてマルテンサイ
ト組織にした後、所定の加熱速度、温度、保持時間で焼
戻しを行うものであるが、次にこの焼戻し条件の限定理
由に付いて述べる。 加熱速度;加熱速度が50℃/sec未満では、昇温の
過程で粒界炭化物が析出、粗大化するため安定して微細
な粒界炭化物を得ることが困難であるため加熱速度の下
限を50℃/secとした。 加熱温度;350℃未満の温度では粒界脆化が顕著にな
り、遅れ破壊特性が悪化する。500℃を超える温度で
は強度が低下し、また安定して微細な粒界炭化物を得る
ことが困難なため、加熱温度域を350℃以上500℃
以下とした。 保持時間;50秒を超える時間保持すると、炭化物が粗
大化する。一方、10秒未満の短時間では均一な焼戻し
マルテンサイト組織を得ることが困難である。従って1
0秒以上50秒以下に限定した。In the method for producing a high-strength PC steel rod according to the present invention,
Immediately after ordinary hot rolling, the steel is quenched to form a martensite structure, and then tempered at a predetermined heating rate, temperature, and holding time. Next, reasons for limiting the tempering conditions will be described. Heating rate: When the heating rate is less than 50 ° C./sec, the lower limit of the heating rate is set to 50 because the grain boundary carbides precipitate and become coarse in the course of raising the temperature, and it is difficult to stably obtain fine grain boundary carbides. ° C / sec. At a heating temperature of less than 350 ° C., grain boundary embrittlement becomes remarkable and delayed fracture characteristics deteriorate. If the temperature exceeds 500 ° C., the strength is reduced, and it is difficult to stably obtain fine grain boundary carbides.
It was as follows. Holding time: If the holding time exceeds 50 seconds, the carbides become coarse. On the other hand, in a short time of less than 10 seconds, it is difficult to obtain a uniform tempered martensite structure. Therefore 1
It was limited to 0 to 50 seconds.
【0016】[0016]
【実施例】供試鋼の化学成分を表1に、熱処理条件、降
伏点、引張強度、伸び、並びに既述の遅れ破壊試験によ
り求めた限界拡散性水素量を表2に示す。(1)〜(1
9)は本発明の高張力鋼棒用鋼の成分、熱処理条件に従
ったものであり、(20)、(22)、(23)、(2
5)〜(43)は比較鋼である。直径7.4mmに熱間
圧延後直ちに水冷し、その後高周波加熱炉によって焼戻
しを行った。熱処理条件は、JIS G 3109 D
種 1号 SBPD 130/145相当の引張強度と
なるように行った。EXAMPLES The chemical composition of the test steel is shown in Table 1, and the heat treatment conditions, yield point, tensile strength, elongation, and critical diffusible hydrogen content obtained by the delayed fracture test described above are shown in Table 2. (1) to (1)
9) is in accordance with the components and heat treatment conditions of the steel for high-strength steel bars of the present invention, and (20) , (22), (23), (2)
5) to (43) are comparative steels. Immediately after hot rolling to a diameter of 7.4 mm, water cooling was performed, and thereafter, tempering was performed in a high-frequency heating furnace. The heat treatment conditions are JIS G 3109 D
The test was performed so that the tensile strength was equivalent to that of seed No. 1 SBPD 130/145.
【0017】[0017]
【表1】 [Table 1]
【0018】[0018]
【表2】 [Table 2]
【0019】この表より、本発明の組成および焼戻し温
度、焼戻し速度の範囲にある(1)〜(19)は、比較
材である(20)、(22)、(23)、(25)〜
(43)に比べて限界水素量が高く、遅れ破壊しにくい
こと、あるいは比較材は添加元素が少なくその効果が見
られないことが明らかである。According to this table, (1) to (19) in the range of the composition, tempering temperature and tempering speed of the present invention are comparative materials (20) , (22), (23) and (25) .
It is clear that the critical hydrogen content is higher than that of (43) and that delayed fracture is less likely to occur, and that the comparative material has little added element and does not show its effect.
【0020】[0020]
【発明の効果】本発明により粒界炭化物のサイズを制御
することによって、JIS G 3109 D種 1号
SBPD 130/145相当の引張強度を有し、耐
遅れ破壊特性の優れたPC鋼棒を製造できる。According to the present invention, by controlling the size of the grain boundary carbide, a PC steel rod having a tensile strength equivalent to JIS G 3109 D type 1 SBPD 130/145 and excellent in delayed fracture resistance is manufactured. it can.
【図1】鋼材の遅れ破壊試験に用いた試験片平面図FIG. 1 is a plan view of a test piece used for a delayed fracture test of a steel material.
【図2】遅れ破壊試験装置の説明図FIG. 2 is an explanatory diagram of a delayed fracture test apparatus.
【図3】水素量分析の水素放出プロファイルFig. 3 Hydrogen release profile of hydrogen content analysis
【図4】限界拡散性水素量の説明図FIG. 4 is an explanatory diagram of a critical diffusible hydrogen amount.
【図5】粒界炭化物サイズが限界拡散性水素量に及ぼす
効果を示すグラフFIG. 5 is a graph showing the effect of grain boundary carbide size on critical diffusible hydrogen content.
1 試験片 2 バランスウェイト 3 支点 1 test piece 2 balance weight 3 fulcrum
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 昭62−267420(JP,A) 特開 昭57−198211(JP,A) 特開 昭47−22813(JP,A) 特公 平1−35066(JP,B2) (58)調査した分野(Int.Cl.7,DB名) C22C 1/00 - 38/60 C21D 8/00 - 8/10 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-267420 (JP, A) JP-A-57-198211 (JP, A) JP-A-47-22813 (JP, A) 35066 (JP, B2) (58) Field surveyed (Int. Cl. 7 , DB name) C22C 1/00-38/60 C21D 8/00-8/10
Claims (4)
で、焼戻しマルテンサイト組織からなり、JIS G
0551による旧オーステナイト粒度番号が10以上で
あるとともに旧オーステナイト粒界の炭化物のサイズが
0.2μm以下であり、且つ強度が145kgf/mm
2 以上であることを特徴とする耐遅れ破壊特性に優れた
高強度鋼棒。C: 0.15 to 0.50% Si: 0.1 to 2.0% Mn: 0.05 to 2.0% P: 0.015% or less S: 0.02% by weight % Or less Al: 0.005 to 0.1%, with the balance being Fe and unavoidable impurities, having a tempered martensitic structure, JIS G
The former austenite grain size number according to 0551 is 10 or more, the size of carbide at the former austenite grain boundary is 0.2 μm or less, and the strength is 145 kgf / mm.
A high-strength steel rod with excellent delayed fracture resistance, characterized by being 2 or more.
で Cr:0.1〜3.0% Mo:0.05〜1.2% Ni:0.05〜2.0% V :0.10〜0.50% Ti:0.005〜0.10% Nb:0.005〜0.10% のうち1種または2種以上を含有することを特徴とする
請求項1記載の耐遅れ破壊特性に優れた高強度鋼棒。2. In addition to the steel component of claim 1, further comprises a weight%
Cr: 0.1 to 3.0% Mo: 0.05 to 1.2% Ni: 0.05 to 2.0% V: 0.10 to 0.50% Ti: 0.005 to 0.10 % Nb: 0.005 to 0.10%, and at least one of them is contained. The high-strength steel rod having excellent delayed fracture resistance according to claim 1.
を、通常の熱間圧延直後に水冷することによってマルテ
ンサイト組織にした後、直ちに350℃〜500℃の温
度範囲に50℃/sec以上の加熱速度で昇温し、10
〜50秒保持して焼戻し、JIS G 0551による
旧オーステナイト粒度番号が10以上であるとともに旧
オーステナイト粒界の炭化物のサイズが0.2μm以下
であり、且つ強度が145kgf/mm 2 以上である焼
戻しマルテンサイト組織からなる鋼棒を得ることを特徴
とする耐遅れ破壊特性に優れた高強度鋼棒の製造方法。3. C: 0.15 to 0.50% by weight% Si: 0.1 to 2.0% Mn: 0.05 to 2.0% P: 0.015% or less S: 0.02 % Or less Al: 0.005 to 0.1%, with the balance being Fe and unavoidable impurities, water-cooled immediately after normal hot rolling to form a martensitic structure, and then immediately 350 ° C to The temperature is raised to a temperature range of 500 ° C. at a heating rate of 50 ° C./sec or more,
Tempering by holding for ~ 50 seconds , according to JIS G 0551
Old austenite particle size number is 10 or more and old
The size of carbide at austenite grain boundary is 0.2μm or less
With a strength of 145 kgf / mm 2 or more
A method for producing a high-strength steel rod having excellent delayed fracture resistance, characterized by obtaining a steel rod having a returned martensite structure .
で Cr:0.1〜3.0% Mo:0.05〜1.2% Ni:0.05〜2.0% V :0.10〜0.50% Ti:0.005〜0.10% Nb:0.005〜0.10% のうち1種または2種以上を含有することを特徴とする
請求項3記載の耐遅れ破壊特性に優れた高強度鋼棒の製
造方法。4. In addition to the steel component according to claim 3, further by weight%
Cr: 0.1 to 3.0% Mo: 0.05 to 1.2% Ni: 0.05 to 2.0% V: 0.10 to 0.50% Ti: 0.005 to 0.10 The method for producing a high-strength steel rod excellent in delayed fracture resistance according to claim 3, wherein one or more of Nb: 0.005 to 0.10% are contained.
Priority Applications (1)
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JP11194194A JP3153071B2 (en) | 1994-04-28 | 1994-04-28 | High-strength steel rod excellent in delayed fracture resistance and method of manufacturing the same |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP11194194A JP3153071B2 (en) | 1994-04-28 | 1994-04-28 | High-strength steel rod excellent in delayed fracture resistance and method of manufacturing the same |
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Publication Number | Publication Date |
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JPH07300651A JPH07300651A (en) | 1995-11-14 |
JP3153071B2 true JP3153071B2 (en) | 2001-04-03 |
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ID=14573988
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JP11194194A Expired - Lifetime JP3153071B2 (en) | 1994-04-28 | 1994-04-28 | High-strength steel rod excellent in delayed fracture resistance and method of manufacturing the same |
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JP (1) | JP3153071B2 (en) |
Families Citing this family (7)
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JP4485424B2 (en) * | 2005-07-22 | 2010-06-23 | 新日本製鐵株式会社 | Manufacturing method of high-strength bolts with excellent delayed fracture resistance |
JP5364859B1 (en) * | 2012-05-31 | 2013-12-11 | 株式会社神戸製鋼所 | High-strength spring steel wire with excellent coiling and hydrogen embrittlement resistance and method for producing the same |
KR101867689B1 (en) * | 2016-09-01 | 2018-06-15 | 주식회사 포스코 | Steel wire rod having excellent hydrogen embrittlement resistance for high strength spring, and method for manufacturing the same |
JP7223997B2 (en) * | 2017-08-18 | 2023-02-17 | 国立大学法人大阪大学 | Steel with high hardness and excellent toughness |
KR102314433B1 (en) * | 2019-12-17 | 2021-10-19 | 주식회사 포스코 | Wire rod for high strength cold head quality steel with excellent resistance to hydrogen embrittlement, and method for manufacturing thereof |
KR102448756B1 (en) * | 2020-12-14 | 2022-09-30 | 주식회사 포스코 | High-strength wire rod with excellent resistance of hydrogen delayed fracture, heat treatment parts using the same, and methods for manufacturing thereof |
KR102463005B1 (en) * | 2020-12-14 | 2022-11-03 | 주식회사 포스코 | High-strength wire rod with excellent hydrogen brittleness resistance, heat treatment parts using the same, and methods for manufacturing thereof |
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- 1994-04-28 JP JP11194194A patent/JP3153071B2/en not_active Expired - Lifetime
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