JP2010121191A - High-strength thick steel plate having superior delayed fracture resistance and weldability, and method for manufacturing the same - Google Patents

High-strength thick steel plate having superior delayed fracture resistance and weldability, and method for manufacturing the same Download PDF

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JP2010121191A
JP2010121191A JP2008297803A JP2008297803A JP2010121191A JP 2010121191 A JP2010121191 A JP 2010121191A JP 2008297803 A JP2008297803 A JP 2008297803A JP 2008297803 A JP2008297803 A JP 2008297803A JP 2010121191 A JP2010121191 A JP 2010121191A
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Tatsuya Kumagai
達也 熊谷
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Nippon Steel Corp
新日本製鐵株式会社
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<P>PROBLEM TO BE SOLVED: To provide a high-strength thick steel plate having superior delayed fracture resistance and weldability, and to provide a method for manufacturing the same. <P>SOLUTION: The high-strength thick steel plate having superior delayed fracture resistance and weldability has a component composition including, by mass%, 0.20-0.26% C, 0.03-0.5% Si, 0.1% or more but less than 0.8% Mn, 0.020% or less P, 0.010% or less S, 0.5-2.0% Cr, 0.1-0.5% Mo, more than 0.10% and equal to or less than 0.30% V, 0.01-0.15% Al, 0.0003-0.0030% B, 0.006% or less N while satisfying Pcm so as to be 0.39% or less; has a martensite structure which occupies 90% or more by a fraction; has a yield strength of 1,300 MPa or higher; and has a tensile strength of 1,400-1,650 MPa. The method for manufacturing the same is also disclosed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

この発明は、建設機械や産業機械の構造部材に用いられる耐遅れ破壊特性および溶接性に優れる降伏強度1300MPa以上で、かつ引張強度1400MPa以上の高強度で、板厚4.5mm以上、25mm以下である高強度厚鋼板およびその製造方法に関する。   The present invention has a yield strength of 1300 MPa or more and excellent tensile strength of 1400 MPa or more, and a plate thickness of 4.5 mm or more and 25 mm or less, which is excellent in delayed fracture resistance and weldability used for structural members of construction machinery and industrial machinery. The present invention relates to a certain high-strength thick steel plate and a manufacturing method thereof.
近年、世界的な建設需要背景に、クレーンやコンクリートポンプ車などの建設機械の生産が伸び続けており、同時にこれら建設機械の大型化が進んでいる。機械の大型化に伴う重量増を抑制するため、構造部材の軽量化ニーズがより高まってきており、降伏強度900MPaないしは1100MPa級の高張力鋼へのシフトが進んでいる。最近ではさらに高強度である、降伏強度1300MPa以上(引張強度1400MPa以上)の構造部材用厚鋼板への要望が高まっている。   In recent years, against the backdrop of global construction demand, production of construction machines such as cranes and concrete pump cars has continued to grow, and at the same time, the size of these construction machines has been increasing. In order to suppress an increase in weight associated with an increase in size of a machine, there is an increasing need for weight reduction of a structural member, and a shift to a high strength steel having a yield strength of 900 MPa or 1100 MPa is progressing. Recently, there is an increasing demand for a thick steel plate for structural members having a higher strength, yield strength of 1300 MPa or more (tensile strength of 1400 MPa or more).
一般に引張強度が1200MPaを超えると水素による遅れ割れが生じる可能性があるとされるので、降伏強度1300MPa級鋼板に対しては、耐遅れ破壊特性が高いことがまず要求される。また、高強度になるほど溶接性では不利となるが、これについても従来の1100MPa級高張力鋼に比べて大きく低下しないことが要求される。   In general, when the tensile strength exceeds 1200 MPa, delayed cracking due to hydrogen may occur. Therefore, the yield strength 1300 MPa grade steel sheet is first required to have high delayed fracture resistance. In addition, the higher the strength, the more disadvantageous the weldability, but this is also required not to be significantly reduced as compared with the conventional 1100 MPa class high strength steel.
降伏強度1300MPa級の構造部材用厚鋼板に関する技術開示については、例えば特許文献1において、引張強度が1370〜1960N/mm級でかつ耐水素脆化特性も優れた鋼板の製造方法が開示されている。しかしながら、特許文献1の技術は1.8mmの冷延板に関するものであり、70℃/sec以上の高い冷速を前提としており、また溶接性についてはなんら考慮されていない。 Regarding the technical disclosure regarding the thick steel plate for structural members having a yield strength of 1300 MPa, for example, Patent Document 1 discloses a method for producing a steel plate having a tensile strength of 1370 to 1960 N / mm 2 and excellent hydrogen embrittlement resistance. Yes. However, the technique of Patent Document 1 relates to a 1.8 mm cold-rolled plate, and is premised on a high cooling speed of 70 ° C./sec or higher, and no consideration is given to weldability.
高強度鋼の耐遅れ破壊特性を向上させる技術としては、従来から結晶粒径を細粒化させる技術が知られている。特許文献2や特許文献3がその例である。しかしこれらの例では、耐遅れ破壊特性を向上させるために、旧オーステナイト結晶粒径を5μm以下あるいは7μm以下とすることを条件としており、厚鋼板をこのようなレベルにまで微細化させることは通常の製造プロセスでは容易ではない。特許文献2や特許文献3において示されているのは、いずれも焼入れ加熱時の急速加熱により旧オーステナイト結晶粒径を微細化させる技術であるが、厚鋼板を急速加熱するためには特殊な加熱設備が必要となるため、実現は難しい。また、結晶粒微細化にともなって焼入性が低下するため、強度を確保するためには合金元素が余計に必要となることから、溶接性や経済性からも過度の結晶粒微細化は好ましくない。   As a technique for improving the delayed fracture resistance of high-strength steel, a technique for reducing the crystal grain size is conventionally known. Examples thereof are Patent Document 2 and Patent Document 3. However, in these examples, in order to improve the delayed fracture resistance, the prior austenite crystal grain size is set to 5 μm or less or 7 μm or less, and it is normal to make a thick steel plate finer to such a level. The manufacturing process is not easy. Both Patent Document 2 and Patent Document 3 show techniques for refining the prior austenite crystal grain size by rapid heating during quenching heating, but special heating is required to rapidly heat thick steel plates. Because equipment is required, it is difficult to realize. In addition, since hardenability decreases as the crystal grain is refined, an extra alloy element is required to ensure strength. Therefore, excessive grain refinement is preferable from the viewpoint of weldability and economy. Absent.
耐摩耗性の要求される用途には、降伏強度1300MPa級に相当する高強度の鋼材が広く使用されており、耐遅れ破壊特性が考慮された鋼材の例もある。例えば、特許文献4は、急速再加熱による焼入れ熱処理で微細なマルテンサイト組織を得て遅れ破壊特性を向上させるとする、引張強度1450MPa〜1600MPaの耐摩耗鋼に関するものである。しかしながら、特許文献4においては鋼材の降伏強度についての記載がない。耐摩耗性に対しては硬さが重要な因子であって、引張強度は耐摩耗性に大きく影響するが、降伏強度はあまり影響しないため、通常耐摩耗鋼では降伏強度は考慮されない。そのため、建設機械や産業機械の構造部材としては適切でないと考えられる。さらに急速再加熱は通常の厚板の熱処理設備では大きな制約となり、厚鋼板への適用は難しい。   High-strength steel materials corresponding to a yield strength of 1300 MPa are widely used for applications requiring wear resistance, and there are examples of steel materials that take into account delayed fracture resistance. For example, Patent Document 4 relates to a wear-resistant steel having a tensile strength of 1450 MPa to 1600 MPa, in which a fine martensite structure is obtained by quenching heat treatment by rapid reheating to improve delayed fracture characteristics. However, in patent document 4, there is no description about the yield strength of steel materials. Hardness is an important factor for wear resistance, and tensile strength has a great influence on wear resistance, but yield strength does not have much influence, so yield strength is not usually considered in wear resistant steel. Therefore, it is thought that it is not suitable as a structural member for construction machinery or industrial machinery. Furthermore, rapid reheating is a major limitation in ordinary thick plate heat treatment equipment and is difficult to apply to thick steel plates.
ボルトにも降伏強度1300MPa級に相当する高強度の鋼が広く使用されており、水素トラップサイトによって耐遅れ破壊特性を考慮させる例が多く提示されている。例えば、特許文献5は、降伏強度130kgf/mm以上、引張強度140kgf/mm以上の、特許文献6は、引張強度1350MPa以上のそれぞれボルト用鋼である。これらはいずれもV、Mo、Crを添加して高温での焼戻し熱処理を行うことで、水素のトラップサイトとなる比較的大きな炭化物を析出させ、耐遅れ破壊特性を向上させているものである。しかしながら、ボルト用鋼では通常溶接性は考慮されず、特許文献5の鋼ではC量が0.35%以上、特許文献6の鋼ではC量が0.30%以上であるため、いずれも溶接性は高くないと考えられる。 High-strength steel corresponding to a yield strength of 1300 MPa class is also widely used for bolts, and many examples have been proposed in which delayed fracture resistance is taken into account by hydrogen trap sites. For example, Patent Document 5 is a steel for bolts having a yield strength of 130 kgf / mm 2 or more and a tensile strength of 140 kgf / mm 2 or more, and Patent Document 6 is a steel for bolts having a tensile strength of 1350 MPa or more. All of them are subjected to tempering heat treatment at a high temperature by adding V, Mo and Cr, thereby precipitating relatively large carbides serving as hydrogen trap sites and improving delayed fracture resistance. However, in steel for bolts, weldability is not normally considered, and the steel of Patent Document 5 has a C content of 0.35% or more, and the steel of Patent Document 6 has a C content of 0.30% or more. The nature is not considered high.
このように、降伏強度1300MPa以上でかつ引張強度1400MPa以上であって、さらに耐遅れ破壊特性や溶接性などの使用性能を具備した構造部材用高強度厚鋼板鋼材を経済的に得るためには、従来の技術では十分ではなかった。
特開平7−90488号公報 特開平11−80903号公報 特開2007−302974号公報 特開平11−229075号公報 特開平6−158170号広報 特開2003−27186号広報
Thus, in order to economically obtain a high-strength thick steel sheet steel for structural members having a yield strength of 1300 MPa or more and a tensile strength of 1400 MPa or more and further having use performance such as delayed fracture resistance and weldability, Conventional technology was not enough.
JP-A-7-90488 Japanese Patent Laid-Open No. 11-80903 JP 2007-302974 A Japanese Patent Laid-Open No. 11-229075 JP-A-6-158170 Japanese Laid-Open Patent Publication No. 2003-27186
本発明の目的は、建設機械や産業機械の構造部材に用いられる耐遅れ破壊特性および溶接性に優れる降伏強度1300MPa以上でかつ引張強度1400MPa以上の構造部材用高強度厚鋼板およびその製造方法を提供することにある。   An object of the present invention is to provide a high-strength thick steel sheet for a structural member having a yield strength of 1300 MPa or higher and a tensile strength of 1400 MPa or higher, which is excellent in delayed fracture resistance and weldability, used for a structural member of a construction machine or an industrial machine, and a manufacturing method thereof. There is to do.
降伏強度1300MPa以上の高強度を得るための最も経済的な手段は、一定温度からの焼入れ熱処理により鋼材組織をマルテンサイトとすることである。マルテンサイト組織を得るためには、鋼の焼入性と冷却速度が適切でなければならない。建設機械や産業機械の構造部材として利用される厚鋼板の板厚は25mm以下がほとんどである。板厚25mmの場合、水冷による焼入れ熱処理時の板厚中心部の冷却速度は通常20℃/sec以上程度であることから、冷却速度20℃/secでもマルテンサイト組織となるのに十分な焼入性を有する鋼材組成が必要となる。   The most economical means for obtaining a high strength with a yield strength of 1300 MPa or more is to make the steel structure martensite by quenching heat treatment from a certain temperature. In order to obtain a martensitic structure, the hardenability and cooling rate of the steel must be appropriate. The thickness of thick steel plates used as structural members for construction machines and industrial machines is almost 25 mm or less. In the case of a plate thickness of 25 mm, the cooling rate at the center of the plate thickness during quenching heat treatment by water cooling is usually about 20 ° C./sec or higher, so that quenching sufficient to form a martensite structure even at a cooling rate of 20 ° C./sec. The steel composition which has the property is required.
焼入性を高め、強度を高めるには合金元素を多く添加すればよいが、合金元素が増加すると溶接性が低下する。発明者は、板厚25mmで、降伏強度1300MPa以上でかつ引張強度1400MPa以上の種々の鋼板について、JIS Z 3158に規定のy型溶接割れ試験を実施し、溶接割れ感受性指標Pcmと、予熱温度との関係を調査した。その結果を図1に示す。溶接施工上の負荷を軽減するためには、できるだけ予熱温度が低いことが望ましい。ここでは、板厚25mmでの割れ停止予熱温度、すなわちルート割れ率が0となる予熱温度が175℃以下であることを溶接性における目標とした。図1から、予熱温度175℃で、ルート割れ率が0となるためのPcmは0.39%以下であり、これを合金添加量の上限のめやすとした。   In order to increase the hardenability and increase the strength, a large amount of alloy element may be added. However, when the alloy element increases, the weldability decreases. The inventor conducted a y-type weld crack test specified in JIS Z 3158 on various steel sheets having a plate thickness of 25 mm, a yield strength of 1300 MPa or more, and a tensile strength of 1400 MPa or more. The weld crack sensitivity index Pcm, the preheating temperature, The relationship was investigated. The result is shown in FIG. In order to reduce the welding load, it is desirable that the preheating temperature is as low as possible. Here, the crack stop preheating temperature at a plate thickness of 25 mm, that is, the preheating temperature at which the root crack rate becomes 0, was set to 175 ° C. or less as a target in weldability. From FIG. 1, the Pcm for the root crack rate to be 0 at a preheating temperature of 175 ° C. is 0.39% or less, and this is considered to be an approximate upper limit of the alloy addition amount.
耐遅れ破壊抑制を向上させる手段として、上述のようにボルト用鋼ではMo、Vなどの炭化物を水素のトラップサイトとして利用する方法が多く提示されている。トラップサイトにはある程度析出物が大きいほうが有利であるため、焼戻し温度は高めであり、強度確保には高いC量と多くの合金元素が必要となる。発明者は、合金量や製造条件を種々変化させて、強度や遅れ破壊特性を調査した結果、(1)Pcmを0.39%以下に抑制しながら1300MPa以上の降伏強度を得るためには、マルテンサイト組織鋼を400℃〜500℃の低温で焼戻し熱処理することがひとつの有効な手段であること、(2)この際C添加量は少なくとも0.20%以上が必要となるが、このようにCが比較的高い場合には、できるだけCrやMo等で焼入性を確保し、Mnは極力低減するほうが強度靭性バランスは向上すること、(3)VおよびCrは、400℃〜500℃の低い焼戻し温度でも炭化物ないしは炭窒化物を生成しやすいことを知見した。   As means for improving delayed fracture resistance, many methods for utilizing carbides such as Mo and V as hydrogen trap sites have been proposed for bolt steel as described above. Since it is advantageous for the trap site to have a large amount of precipitates, the tempering temperature is high, and a high amount of C and many alloy elements are required to ensure the strength. As a result of investigating the strength and delayed fracture characteristics by varying the amount of alloy and manufacturing conditions in various ways, (1) In order to obtain a yield strength of 1300 MPa or more while suppressing Pcm to 0.39% or less, It is one effective means to temper the martensitic steel at a low temperature of 400 ° C. to 500 ° C. (2) At this time, the amount of C added must be at least 0.20%. When C is relatively high, the hardenability is ensured with Cr, Mo, etc. as much as possible, and the balance of strength and toughness is improved by reducing Mn as much as possible. (3) V and Cr are 400 ° C to 500 ° C. It has been found that carbides or carbonitrides are easily formed even at a low tempering temperature.
耐遅れ破壊特性の評価は、遅れ破壊試験で破断しない水素量の上限値である「限界拡散性水素量」で評価した。この方法は、鉄と鋼Vol.83(1997)、p454に記載の方法である。具体的には、図2に示す形状の切り欠き付き試験片に、丸棒電解水素チャージにより種々のレベルの拡散性水素量を試料に含有させた後、試料表面にめっき処理を施して水素の逸散を防止する。これに大気中で所定の荷重を負荷して保持し、遅れ破壊が発生するまでの時間を測定する。遅れ破壊試験における負荷応力は、それぞれ鋼材の引張強度の0.8倍とした。図3は、拡散性水素量と遅れ破壊に至るまでの破断時間の関係の一例である。試料中に含まれる拡散性水素量が少なくなるほど遅れ破壊に至るまでの時間が長くなり、拡散性水素量がある値以下では遅れ破壊が発生しなくなる。試験後すみやかに試験片を回収して、100℃/hrの昇温条件でガスクロマトグラフで測定した拡散性水素量の積分値「拡散性水素量」とし、破断しなくなる限界の水素量を「限界拡散性水素量Hc」と定義する。   The delayed fracture resistance was evaluated by the “limit diffusible hydrogen content” which is the upper limit of the hydrogen content that does not break in the delayed fracture test. This method is disclosed in Iron and Steel Vol. 83 (1997), p454. Specifically, the sample with notches having the shape shown in FIG. 2 was charged with various levels of diffusible hydrogen by round bar electrolytic hydrogen charging, and then the surface of the sample was subjected to plating treatment to produce hydrogen. Prevent dissipation. A predetermined load is applied and held in the atmosphere, and the time until delayed fracture occurs is measured. The load stress in the delayed fracture test was 0.8 times the tensile strength of each steel material. FIG. 3 is an example of the relationship between the amount of diffusible hydrogen and the fracture time until delayed fracture. The smaller the amount of diffusible hydrogen contained in the sample, the longer the time until delayed fracture occurs. When the amount of diffusible hydrogen is less than a certain value, delayed fracture does not occur. Immediately after the test, the test piece is collected, and the integral value of the amount of diffusible hydrogen measured with a gas chromatograph under a temperature rising condition of 100 ° C./hr is set to “diffusible hydrogen amount”. It is defined as “diffusible hydrogen amount Hc”.
一方、環境から鋼材に侵入する水素量も鋼材の冶金的因子によって変化する。環境からの侵入水素を評価するため、腐食促進試験を行った。この試験は、5mass%NaCl溶液を用いて、図4に示すサイクルで30日間乾湿繰り返しを行う試験である。試験後、鋼材中に侵入した水素量を同じ昇温条件によるガスクロマトグラフで測定し、これを「環境から侵入する拡散性水素量HE」と定義した。
「限界拡散性水素量Hc」が「環境から侵入する拡散性水素量HE」よりも相対的に十分高いと、遅れ破壊感受性が低いと考えられる。Hc/HEが3よりも大きい場合に、遅れ破壊感受性が低く、耐遅れ破壊特性が良好であると評価した。
また、引張強度が1650MPaを超えると曲げ加工性が大きく低下するので、これを引張強度の上限とする。
これらの知見により、降伏強度1300MPa以上、かつ引張強度1400MPa以上で、耐遅れ破壊特性、曲げ加工性、および溶接性に優れる板厚4.5mm〜25mmの厚鋼板を得ることができる。
On the other hand, the amount of hydrogen that enters the steel from the environment also varies depending on the metallurgical factors of the steel. In order to evaluate intrusion hydrogen from the environment, a corrosion acceleration test was conducted. This test is a test in which drying and wetting is repeated for 30 days in the cycle shown in FIG. 4 using a 5 mass% NaCl solution. After the test, the amount of hydrogen that had entered the steel material was measured by a gas chromatograph under the same temperature rise conditions, and this was defined as “the amount of diffusible hydrogen intruding from the environment HE”.
If the “limit diffusible hydrogen amount Hc” is relatively sufficiently higher than the “diffusible hydrogen amount HE entering from the environment”, the delayed fracture susceptibility is considered to be low. When Hc / HE was larger than 3, it was evaluated that delayed fracture susceptibility was low and delayed fracture resistance was good.
Further, if the tensile strength exceeds 1650 MPa, the bending workability is greatly reduced, so this is the upper limit of the tensile strength.
Based on these findings, a thick steel plate having a yield strength of 1300 MPa or more and a tensile strength of 1400 MPa or more and excellent in delayed fracture resistance, bending workability, and weldability can be obtained.
本発明の要旨とするところは下記のとおりである。
(1)質量%で、C:0.20%以上、0.26%以下、Si:0.03%以上、0.5%以下、Mn:0.1%以上、0.8%未満、P:0.020%以下、S:0.010%以下、Cr:0.5%以上、2.0%以下、Mo:0.1%以上、0.5%以下、V:0.10%超、0.30%以下、Al:0.01%以上、0.15%以下、B:0.0003%以上、0.0030%以下、N:0.006%以下を含み、その他Feおよび不可避的不純物からなり、かつ下記Pcmが0.39%以下であることを満たす成分組成を有し、マルテンサイト組織分率が90%以上であり、降伏強度が1300MPa以上であり、引張強度が1400MPa以上、1650MPa以下であることを特徴とする、耐遅れ破壊特性および溶接性に優れる高強度厚鋼板。 Pcm=[C]+[Si]/30+[Mn]/20+[Cu]/20+[Ni]/60+[Cr]/20+[Mo]/15+[V]/10+5[B] ここで、[C]、[Si]、[Mn]、[Cu]、[Ni]、[Cr]、[Mo]、[V]、[B]はそれぞれ、C、Si、Mn、Cu、Ni、Cr、Mo、V、Bの質量%である。
The gist of the present invention is as follows.
(1) By mass%, C: 0.20% or more, 0.26% or less, Si: 0.03% or more, 0.5% or less, Mn: 0.1% or more, less than 0.8%, P : 0.020% or less, S: 0.010% or less, Cr: 0.5% or more, 2.0% or less, Mo: 0.1% or more, 0.5% or less, V: more than 0.10% 0.30% or less, Al: 0.01% or more, 0.15% or less, B: 0.0003% or more, 0.0030% or less, N: 0.006% or less, other Fe and unavoidable It has a component composition that consists of impurities and satisfies the following Pcm of 0.39% or less, the martensite structure fraction is 90% or more, the yield strength is 1300 MPa or more, the tensile strength is 1400 MPa or more, Excellent delayed fracture resistance and weldability, characterized by being 1650 MPa or less Strength steel plate. Pcm = [C] + [Si] / 30 + [Mn] / 20 + [Cu] / 20 + [Ni] / 60 + [Cr] / 20 + [Mo] / 15 + [V] / 10 + 5 [B] where [C] , [Si], [Mn], [Cu], [Ni], [Cr], [Mo], [V], and [B] are C, Si, Mn, Cu, Ni, Cr, Mo, and V, respectively. , B mass%.
(2)質量%で、さらに、Cu:0.1%以上、0.5%以下、Ni:0.1%以上、2.0%以下、Nb:0.003%以上、0.10%以下、Ti:0.005%以上、0.05%以下のうちの1種または2種を含有することを特徴とする、(1)に記載の、耐遅れ破壊特性および溶接性に優れる厚鋼板。 (2) By mass%, Cu: 0.1% or more, 0.5% or less, Ni: 0.1% or more, 2.0% or less, Nb: 0.003% or more, 0.10% or less Ti: A thick steel plate excellent in delayed fracture resistance and weldability according to (1), characterized by containing one or two of 0.005% or more and 0.05% or less.
(3)(1)または(2)に記載の成分組成を有する鋼片または鋳片を1100℃以上に加熱し、熱間圧延を行って板厚4.5mm以上、25mm以下の鋼板とし、直ちに600℃から300℃までの板厚中心部における平均冷却速度が20℃/sec以上となる冷却条件で200℃以下まで加速冷却を行うか、またはAc3変態点+20℃以上の温度に再加熱した後に、600℃から300℃までの板厚中心部における平均冷却速度が20℃/sec以上となる冷却条件で200℃以下まで加速冷却を行い、さらにその後400℃以上、500℃以下の温度範囲で焼戻し熱処理を行うことを特徴とする、耐遅れ破壊特性および溶接性に優れる高強度厚鋼板の製造方法。 (3) A steel slab or cast slab having the composition described in (1) or (2) is heated to 1100 ° C. or higher and hot rolled to obtain a steel plate having a thickness of 4.5 mm or more and 25 mm or less. After accelerated cooling to 200 ° C. or lower under cooling conditions where the average cooling rate at the center of the plate thickness from 600 ° C. to 300 ° C. is 20 ° C./sec or higher, or after reheating to a temperature of Ac 3 transformation point + 20 ° C. or higher , Accelerated cooling to 200 ° C. or lower under cooling conditions where the average cooling rate at the center of the plate thickness from 600 ° C. to 300 ° C. is 20 ° C./sec or higher, and then tempering in a temperature range of 400 ° C. or higher and 500 ° C. or lower. A method for producing a high-strength thick steel plate excellent in delayed fracture resistance and weldability, characterized by performing heat treatment.
本発明によれば、建設機械や産業機械の構造部材に用いられる、耐遅れ破壊特性および溶接性に優れる降伏強度1300MPa以上でかつ引張強度1400MPa以上の厚鋼板を経済的に提供することができる。   According to the present invention, it is possible to economically provide a thick steel plate having a yield strength of 1300 MPa or more and a tensile strength of 1400 MPa or more, which is excellent in delayed fracture resistance and weldability, which is used for structural members of construction machines and industrial machines.
以下、本発明について詳細に説明する。
まず、本発明の鋼成分の限定理由を述べる。
Cは、マルテンサイト組織の強度に大きく影響する重要な元素である。C含有量は、本発明において板厚4.5mm〜25mmまでの範囲で、マルテンサイト組織分率が90%以上であるときに、1300MPa以上の降伏強度と、1400MPa以上の引張強度を得るために必要な量として、0.20%以上を添加する。また、過剰のC添加により、溶接性が低下することや、引張強度が1650MPaを超えることがあるので、添加量は0.26%以下とする。
Hereinafter, the present invention will be described in detail.
First, the reasons for limiting the steel components of the present invention will be described.
C is an important element that greatly affects the strength of the martensite structure. In order to obtain a yield strength of 1300 MPa or more and a tensile strength of 1400 MPa or more when the C content is in the range from 4.5 mm to 25 mm in the present invention and the martensite structure fraction is 90% or more. As a necessary amount, 0.20% or more is added. Moreover, since weldability may fall by excess C addition, and tensile strength may exceed 1650 Mpa, an addition amount shall be 0.26% or less.
Siは、脱酸材および強化元素として作用し、0.03%以上の添加でその効果が認められるが、多く添加すると靭性を阻害することがあるため、上限を0.5%とする。   Si acts as a deoxidizing material and a strengthening element, and its effect is recognized when added in an amount of 0.03% or more. However, if added in a large amount, the toughness may be inhibited, so the upper limit is made 0.5%.
Mnは、焼入性を高めるのに有効な元素であるが、本発明鋼のようにCが0.20%以上と比較的高いマルテンサイト組織鋼を400℃〜500℃で焼戻す場合には、むしろMnを低減したほうが強度靭性バランスを向上させることができる。したがって、Mnは焼入れ性確保のために0.1%以上を添加するが、添加の上限を0.8%未満、望ましくは0.5%以下とする。   Mn is an element effective for enhancing hardenability, but when martensitic steel having a relatively high C of 0.20% or more is tempered at 400 ° C. to 500 ° C. as in the steel of the present invention. Rather, the balance of strength and toughness can be improved by reducing Mn. Therefore, Mn is added in an amount of 0.1% or more for ensuring hardenability, but the upper limit of addition is less than 0.8%, preferably 0.5% or less.
Pは、不可避的不純物として、高強度鋼の溶接性を低下させる有害な元素である。したがって、含有量を0.020%以下に抑制する。   P is a harmful element that deteriorates the weldability of high-strength steel as an inevitable impurity. Therefore, the content is suppressed to 0.020% or less.
Sは、やはり不可避的不純物として、耐遅れ破壊特性を低下させる有害な元素である。したがって、含有量を0.010%以下に抑制する。   S is also an inevitable impurity and is a harmful element that lowers the delayed fracture resistance. Therefore, the content is suppressed to 0.010% or less.
Crは、焼入性を向上させ、400℃〜500℃での焼戻しを行う場合には析出強化や、水素のトラップサイト生成に有効であるので、0.5%以上添加する。しかしながら、過剰に添加すると靭性を低下させることがあるため、添加は2.0%以下とする。   Cr improves hardenability and is effective for precipitation strengthening and hydrogen trap site generation when tempering at 400 ° C. to 500 ° C. is performed, so 0.5% or more is added. However, if added excessively, the toughness may be lowered, so the addition is made 2.0% or less.
Moは、焼入性を向上させ、400℃〜500℃での焼戻しによって析出強化効果もあることから、0.1%以上添加する。しかしながら、多量に添加すると溶接性を低下させることがあるので、添加は0.5%以下とする。   Mo improves hardenability and also has a precipitation strengthening effect by tempering at 400 ° C. to 500 ° C., so 0.1% or more is added. However, if a large amount is added, weldability may be lowered, so the addition is made 0.5% or less.
Alは、脱酸剤あるいは、焼入性向上に必要なフリーBを確保するためにNを固定する目的で添加するが、過剰な添加は靭性を低下させる場合がある。このため、Alの添加量は0.01%以上、0.15%以下とする。   Al is added for the purpose of fixing N in order to secure a deoxidizer or free B necessary for improving hardenability, but excessive addition may reduce toughness. For this reason, the addition amount of Al shall be 0.01% or more and 0.15% or less.
Vは焼入性を向上させ、400℃〜500℃での焼戻しを行う場合には析出強化効果があり、さらに炭化物あるいは窒化物は、水素のトラップサイトとして有効であるので、本発明においては0.10%超の添加を必須とする。しかしながら、多量に添加すると溶接性を低下させるため、添加は0.30%以下とする。   V improves the hardenability and has a precipitation strengthening effect when tempering at 400 ° C. to 500 ° C. Further, since carbide or nitride is effective as a hydrogen trap site, it is 0 in the present invention. • Addition of more than 10% is essential. However, if added in a large amount, the weldability is lowered, so the addition is made 0.30% or less.
Bは、焼入性を高めるために有効な必須元素である。その効果を発揮するには0.0003%以上必要であるが、0.0030%を超えて添加すると溶接性や靭性を低下させることがあるので、Bの含有量は0.0003%以上、0.0030%以下とする。   B is an essential element effective for enhancing the hardenability. In order to exert the effect, 0.0003% or more is necessary, but if added over 0.0030%, the weldability and toughness may be lowered, so the B content is 0.0003% or more, 0 0030% or less.
Nは、過剰に含有されると靱性を低下させるとともに、BNを形成してBの焼入性向上効果を阻害するので、含有量を0.006%以下に抑制する。   If N is contained excessively, it lowers toughness and inhibits the effect of improving the hardenability of B by forming BN, so the content is suppressed to 0.006% or less.
以上は本発明における鋼の基本成分であるが、さらに本発明では上記成分の他に、Cu、Ni、Nb、Tiのうち一種または二種以上添加することができる。
Cuは、強化のため添加してもよいが、その効果は限定的であり、高価な元素でもあるため添加する場合には0.1%以上、0.5%以下の添加量とする。
The above are the basic components of steel in the present invention, but in the present invention, one or more of Cu, Ni, Nb and Ti can be added in addition to the above components.
Cu may be added for strengthening, but its effect is limited, and since it is an expensive element, the addition amount is 0.1% or more and 0.5% or less.
Niは焼入性を向上させ、靭性を向上させる効果があり、これらの目的のためには0.1%以上を添加する。しかし、Niは高価な元素であるので、添加する場合でも上限を2.0%とする。   Ni has the effect of improving hardenability and improving toughness, and for these purposes, 0.1% or more is added. However, since Ni is an expensive element, even when it is added, the upper limit is made 2.0%.
Nbは、圧延中に微細炭化物鋼を生成して未再結晶温度域を広げて制御圧延効果を高める効果や、ピニングにより焼入れ加熱時のオーステナイト粗大化を抑制する効果があるので、靭性向上に有効である。この目的のために添加するときには0.003%以上を添加する。しかし過剰に添加すると溶接性を阻害することがあるため、添加量は0.10%以下とする。   Nb is effective in improving toughness because it produces fine carbide steel during rolling and expands the non-recrystallization temperature range to increase the controlled rolling effect and suppresses austenite coarsening during quenching heating by pinning. It is. When added for this purpose, 0.003% or more is added. However, if added excessively, weldability may be hindered, so the added amount is made 0.10% or less.
Tiは、特に熱間圧延終了後直ちに加速冷却を行う際に、焼入性向上に必要なフリーBを確保するためにNを固定する目的で添加するが、過剰な添加は溶接性や靭性を低下させる場合がある。このため、Tiを添加する場合、その添加量は0.005%以上、0.05%以下とする。   Ti is added for the purpose of fixing N in order to secure the free B necessary for improving the hardenability, particularly when accelerated cooling is performed immediately after the end of hot rolling. However, excessive addition reduces weldability and toughness. May decrease. For this reason, when adding Ti, the addition amount shall be 0.005% or more and 0.05% or less.
以上の成分範囲の限定に加え、上述したように本発明では、溶接性を確保するため、下記Pcmが0.39%以下となるように成分組成を限定する。
Pcm=[C]+[Si]/30+[Mn]/20+[Cu]/20+[Ni]/60+[Cr]/20+[Mo]/15+[V]/10+5[B]であり、ここで、[C]、[Si]、[Mn]、[Cu]、[Ni]、[Cr]、[Mo]、[V]、[B]はそれぞれ、C、Si、Mn、Cu、Ni、Cr、Mo、V、Bの質量%である。
In addition to the above component range limitation, as described above, in the present invention, in order to ensure weldability, the component composition is limited so that the following Pcm is 0.39% or less.
Pcm = [C] + [Si] / 30 + [Mn] / 20 + [Cu] / 20 + [Ni] / 60 + [Cr] / 20 + [Mo] / 15 + [V] / 10 + 5 [B], where [C], [Si], [Mn], [Cu], [Ni], [Cr], [Mo], [V], and [B] are C, Si, Mn, Cu, Ni, Cr, It is the mass% of Mo, V, and B.
次に製造方法について述べる。
まず、上記の鋼成分組成の鋼片または鋳片を加熱して熱間圧延を行う。加熱温度はNbやVが十分固溶するように、1100℃以上とする。
Next, a manufacturing method will be described.
First, hot rolling is performed by heating a steel slab or slab having the above steel composition. The heating temperature is set to 1100 ° C. or higher so that Nb and V are sufficiently dissolved.
熱間圧延を行って板厚4.5mm以上、25mm以下の鋼板とし、熱間圧延終了後直ちに600℃から300℃までの板厚中心部における平均冷却速度が20℃/sec以上となる冷却条件で200℃以下まで加速冷却を行うか、あるいは熱間圧延終了後いったん冷却した後にAc3変態点+20℃以上の温度に再加熱した後に、600℃から300℃までの板厚中心部における平均冷却速度が20℃/sec以上となる冷却条件で200℃以下まで加速冷却を行う。再加熱焼入れの場合の焼入れ加熱温度は当然Ac3温度より高くなくてはならないが、加熱温度をAc3温度の直上とすると、組織が混粒になり焼入性や靭性が不十分となる場合があるので、焼入れ加熱温度はAc3+20℃以上とする。加速冷却は、いずれも板厚4.5mmから25mmまでの鋼板において組織分率で90%以上のマルテンサイト組織を得ることが目的である。   A steel sheet having a thickness of 4.5 mm or more and 25 mm or less by performing hot rolling, and a cooling condition in which the average cooling rate at the center of the thickness from 600 ° C. to 300 ° C. immediately after the hot rolling is 20 ° C./sec or more. Accelerated cooling to 200 ° C. or lower after cooling, or after cooling once after the hot rolling, and then reheating to a temperature of Ac3 transformation point + 20 ° C. or higher, then the average cooling rate at the center of the plate thickness from 600 ° C. to 300 ° C. Accelerated cooling is performed to 200 ° C. or lower under a cooling condition of 20 ° C./sec or higher. In the case of reheating and quenching, the quenching heating temperature must naturally be higher than the Ac3 temperature. However, if the heating temperature is just above the Ac3 temperature, the structure becomes mixed and the hardenability and toughness may be insufficient. Therefore, quenching heating temperature shall be Ac3 + 20 degreeC or more. The purpose of accelerated cooling is to obtain a martensite structure having a structure fraction of 90% or more in a steel sheet having a thickness of 4.5 mm to 25 mm.
加速冷却後の鋼板に400℃以上、500℃以下の温度範囲で焼戻し熱処理を行うことにより、マルテンサイト組織の焼戻し効果と、Cr、Mo、Vなどの炭化物または炭窒化物の析出強化効果により強度靭性バランスを向上さるとともに、特に水素トラップサイトとして有効なVとCrの炭化物または炭窒化物を生成させる。焼戻し熱処理の時間は30分程度以上であればよい。   By performing tempering heat treatment on the steel sheet after accelerated cooling at a temperature range of 400 ° C. or higher and 500 ° C. or lower, the strength is improved by the tempering effect of martensite structure and the precipitation strengthening effect of carbides such as Cr, Mo, V, or carbonitrides. It improves the toughness balance and produces V and Cr carbides or carbonitrides that are particularly effective as hydrogen trap sites. The time for the tempering heat treatment may be about 30 minutes or more.
表1に示す成分組成を有するA〜AFの鋼を溶製して得られた鋼片を、表2に示す1〜16の本発明例と17〜42の比較例それぞれの製造条件により、板厚4.5〜25mmの鋼板を製造した。   The steel pieces obtained by melting the steels A to A F having the composition shown in Table 1 are obtained according to the production conditions of the present invention examples 1 to 16 and the comparative examples 17 to 42 shown in Table 2, respectively. Steel plates having a thickness of 4.5 to 25 mm were manufactured.
これらの鋼板について、降伏強度、引張強度、マルテンサイト組織分率、溶接割れ性、耐遅れ破壊特性、靭性を評価した。
降伏強度と引張強度は、JIS Z 2201に規定の1A号引張試験片を採取して、JIS Z 2241に規定の引張試験により測定した。
溶接割れ性は、JIS Z 3158に規定のy型溶接割れ試験での評価を行った。溶接条件はCO2溶接で入熱15kJ/cmであり、評価に供した鋼板の板厚はすべて25mmである。試験の結果、予熱温度175℃でルート割れ率が0となれば合格と評価した。また、板厚が25mm未満の実施例2、4、8、13の鋼板については、溶接性は同一成分の実施例1、3、7、12と同じと考えられることから、y型溶接割れ試験は省略した。
These steel plates were evaluated for yield strength, tensile strength, martensite structure fraction, weld cracking property, delayed fracture resistance, and toughness.
Yield strength and tensile strength were measured by taking a No. 1A tensile test piece specified in JIS Z 2201 and performing a tensile test specified in JIS Z 2241.
The weld cracking property was evaluated by a y-type weld cracking test specified in JIS Z 3158. The welding conditions were CO2 welding with a heat input of 15 kJ / cm, and the plate thicknesses of the steel plates used for the evaluation were all 25 mm. As a result of the test, if the root cracking rate was 0 at a preheating temperature of 175 ° C., it was evaluated as acceptable. In addition, for the steel plates of Examples 2, 4, 8, and 13 having a plate thickness of less than 25 mm, the weldability is considered to be the same as that of Examples 1, 3, 7, and 12 of the same component. Omitted.
耐遅れ破壊特性の評価は、それぞれの鋼板の「限界拡散性水素量Hc」および「環境から侵入する拡散性水素量HE」を測定し、Hc/HEが3より大きい場合に、耐遅れ破壊特性が良好であると評価した。   Delayed fracture resistance is evaluated by measuring the “limit diffusible hydrogen amount Hc” and “diffusible hydrogen amount HE entering from the environment” of each steel sheet. When Hc / HE is greater than 3, delayed fracture resistance Was evaluated as being good.
靱性はJIS Z 2201 4号シャルピー試験片を板厚中心部から圧延方向に直角に採取し、−20℃における衝撃試験の吸収エネルギー値を、3本の試験片の平均値で評価し、27Jを目標値とした。なお、板厚が4.5mmの鋼板については3mmサブサイズのシャルピー試験片とし、1cmあたりの吸収エネルギー値が27J以上であることを目標値とした。 As for toughness, a JIS Z 2201 No. 4 Charpy test piece was sampled perpendicularly to the rolling direction from the center of the plate thickness, and the absorbed energy value of the impact test at −20 ° C. was evaluated by the average value of the three test pieces. The target value was used. In addition, about the steel plate whose plate | board thickness is 4.5 mm, it was set as the target value that it was set as the Charpy test piece of 3 mm subsize, and the absorbed energy value per 1 cm < 2 > was 27J or more.
なお、表1中で下線を付した化学成分、Pcm値の数値は、その値が本発明外であることを示し、表2中で下線を付した数値は、製造条件が本発明外であること、あるいは特性が不十分なものを示している。   The underlined chemical composition and Pcm values in Table 1 indicate that the values are outside the scope of the present invention, and the underlined numbers in Table 2 indicate that the manufacturing conditions are outside the scope of the present invention. This indicates that the characteristics are insufficient.
表2の本発明例1〜16においては、すべて前記の降伏強度、引張強度、マルテンサイト組織分率、溶接割れ性、耐遅れ破壊特性、靭性の目標値を満足している。これに対し、表中下線で示す化学成分が本発明により限定された範囲を逸脱している比較例17〜36においては、製造法は本発明法であるにもかかわらず、降伏強度、引張強度、マルテンサイト組織分率、溶接割れ性、耐遅れ破壊特性、靭性のうちひとつ以上で目標値に満たない。鋼成分組成は本発明範囲内であるが、Pcm値が本発明範囲を逸脱している比較例37は、溶接割れ性が不合格である。鋼成分組成、Pcm値がいずれも本発明範囲内であっても、加熱温度の低い比較例38は、降伏強度が不十分であり、焼入れ加熱温度がAc3+20℃よりも低い比較例39も、降伏強度が不十分となり、600℃から300℃までの冷却速度の小さい比較例40は90%以上のマルテンサイト組織分率が得られないため降伏強度および引張強度が低く、焼戻しをしない比較例41は、降伏強度が低く、焼戻し温度が500℃を超えている比較例42は、降伏強度が低い。   In Invention Examples 1 to 16 in Table 2, all of the above-described target values of yield strength, tensile strength, martensite structure fraction, weld cracking property, delayed fracture resistance, and toughness are satisfied. On the other hand, in Comparative Examples 17 to 36 in which the chemical components indicated by the underline in the table deviate from the range limited by the present invention, the yield strength and tensile strength were determined even though the production method was the method of the present invention. , One or more of martensite structure fraction, weld cracking property, delayed fracture resistance, and toughness is less than the target value. Although the steel component composition is within the range of the present invention, Comparative Example 37 in which the Pcm value deviates from the range of the present invention has a poor weld cracking property. Even if the steel component composition and the Pcm value are both within the range of the present invention, the comparative example 38 having a low heating temperature has insufficient yield strength, and the comparative example 39 having a quenching heating temperature lower than Ac3 + 20 ° C is also a yield. In Comparative Example 40, the strength is insufficient and the cooling rate from 600 ° C. to 300 ° C. is small, and a martensite structure fraction of 90% or more cannot be obtained. In Comparative Example 42, the yield strength is low and the tempering temperature exceeds 500 ° C., the yield strength is low.
Pcmとy型溶接割れ試験における割れ停止予熱温度との関係を示すグラフである。It is a graph which shows the relationship between Pcm and the crack stop preheating temperature in a y-type weld crack test. 耐水素脆化特性評価用切欠き試験片の説明図である。It is explanatory drawing of the notch test piece for hydrogen embrittlement resistance evaluation. 拡散性水素量と遅れ破壊に至るまでの破断時間の関係の一例を示すグラフである。It is a graph which shows an example of the relationship between the amount of diffusible hydrogen, and the fracture | rupture time until it leads to delayed fracture. 腐食促進試験の、乾湿および温度の繰り返し条件を示すグラフである。It is a graph which shows the repetition conditions of wet and dry and temperature of a corrosion acceleration test.

Claims (3)

  1. 質量%で、
    C:0.20%以上、0.26%以下、
    Si:0.03%以上、0.5%以下、
    Mn:0.1%以上、0.8%未満、
    P:0.020%以下、
    S:0.010%以下、
    Cr:0.5%以上、2.0%以下、
    Mo:0.1%以上、0.5%以下、
    V:0.10%超、0.30%以下、
    Al:0.01%以上、0.15%以下、
    B:0.0003%以上、0.0030%以下、
    N:0.006%以下
    を含み、その他Feおよび不可避的不純物からなり、かつ下記Pcmが0.39%以下であることを満たす成分組成を有し、マルテンサイト組織分率が90%以上であり、降伏強度が1300MPa以上であり、引張強度が1400MPa以上、1650MPa以下であることを特徴とする耐遅れ破壊特性および溶接性に優れる高強度厚鋼板。
    Pcm=[C]+[Si]/30+[Mn]/20+[Cu]/20+[Ni]/60+[Cr]/20+[Mo]/15+[V]/10+5[B]
    ここで、[C]、[Si]、[Mn]、[Cu]、[Ni]、[Cr]、[Mo]、[V]、[B]はそれぞれ、C、Si、Mn、Cu、Ni、Cr、Mo、V、Bの質量%である。
    % By mass
    C: 0.20% or more, 0.26% or less,
    Si: 0.03% or more, 0.5% or less,
    Mn: 0.1% or more, less than 0.8%,
    P: 0.020% or less,
    S: 0.010% or less,
    Cr: 0.5% or more, 2.0% or less,
    Mo: 0.1% or more, 0.5% or less,
    V: more than 0.10%, 0.30% or less,
    Al: 0.01% or more, 0.15% or less,
    B: 0.0003% or more, 0.0030% or less,
    N: 0.006% or less, composed of other Fe and unavoidable impurities, satisfying the following Pcm of 0.39% or less, martensite structure fraction is 90% or more A high strength thick steel plate excellent in delayed fracture resistance and weldability, characterized in that the yield strength is 1300 MPa or more and the tensile strength is 1400 MPa or more and 1650 MPa or less.
    Pcm = [C] + [Si] / 30 + [Mn] / 20 + [Cu] / 20 + [Ni] / 60 + [Cr] / 20 + [Mo] / 15 + [V] / 10 + 5 [B]
    Here, [C], [Si], [Mn], [Cu], [Ni], [Cr], [Mo], [V], and [B] are C, Si, Mn, Cu, and Ni, respectively. , Cr, Mo, V, B mass%.
  2. 質量%で、さらに、
    Cu:0.1%以上、0.5%以下、
    Ni:0.1%以上、2.0%以下、
    Nb:0.003%以上、0.10%以下、
    Ti:0.005%以上、0.05%以下
    のうちの1種または2種を含有することを特徴とする請求項1に記載の耐遅れ破壊特性および溶接性に優れる厚鋼板。
    In mass%,
    Cu: 0.1% or more, 0.5% or less,
    Ni: 0.1% or more, 2.0% or less,
    Nb: 0.003% or more, 0.10% or less,
    The thick steel plate excellent in delayed fracture resistance and weldability according to claim 1, characterized in that it contains one or two of Ti: 0.005% or more and 0.05% or less.
  3. 請求項1または請求項2に記載の成分組成を有する鋼片または鋳片を1100℃以上に加熱し、熱間圧延を行って板厚4.5mm以上、25mm以下の厚鋼板とし、直ちに600℃から300℃までの板厚中心部における平均冷却速度が20℃/sec以上となる冷却条件で200℃以下まで加速冷却を行うか、または該厚鋼板をAc3変態点+20℃以上の温度に再加熱した後に、600℃から300℃までの板厚中心部における平均冷却速度が20℃/sec以上となる冷却条件で200℃以下まで加速冷却を行い、さらにその後400℃以上、500℃以下の温度範囲で焼戻し熱処理を行うことを特徴とする、耐遅れ破壊特性および溶接性に優れる高強度厚鋼板の製造方法。
    The steel slab or slab having the component composition according to claim 1 or 2 is heated to 1100 ° C or higher and hot rolled to obtain a steel plate having a thickness of 4.5 mm or more and 25 mm or less, and immediately 600 ° C. Accelerated cooling to 200 ° C. or lower under cooling conditions in which the average cooling rate at the center of the plate thickness from 20 to 300 ° C. is 20 ° C./sec or higher, or reheat the thick steel plate to a temperature of Ac 3 transformation point + 20 ° C. or higher. After that, accelerated cooling is performed to 200 ° C. or lower under cooling conditions in which the average cooling rate at the center of the plate thickness from 600 ° C. to 300 ° C. is 20 ° C./sec or higher, and then the temperature range is 400 ° C. or higher and 500 ° C. or lower. A method for producing a high-strength thick steel plate excellent in delayed fracture resistance and weldability, characterized by performing tempering heat treatment at
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WO2012133910A1 (en) * 2011-03-29 2012-10-04 Jfeスチール株式会社 Abrasion-resistant steel sheet exhibiting excellent resistance to stress corrosion cracking, and method for producing same
US20130040165A1 (en) * 2011-08-10 2013-02-14 Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) High-strength steel sheet excellent in seam weldability
CN104204254A (en) * 2012-03-26 2014-12-10 株式会社神户制钢所 Boron-added high strength bolt steel having excellent delayed fracture resistance and high strength bolt
WO2015194572A1 (en) * 2014-06-16 2015-12-23 株式会社神戸製鋼所 Ultra-high-strength steel sheet having excellent collision characteristics
CN107988553A (en) * 2017-11-28 2018-05-04 钢铁研究总院 A kind of high tenacity high speed axles steel and its heat treatment method
US9982331B2 (en) 2012-09-19 2018-05-29 Jfe Steel Corporation Abrasion resistant steel plate having excellent low-temperature toughness and excellent corrosive wear resistance
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WO2012133910A1 (en) * 2011-03-29 2012-10-04 Jfeスチール株式会社 Abrasion-resistant steel sheet exhibiting excellent resistance to stress corrosion cracking, and method for producing same
US9879334B2 (en) 2011-03-29 2018-01-30 Jfe Steel Corporation Abrasion resistant steel plate or steel sheet excellent in resistance to stress corrosion cracking and method for manufacturing the same
US10030291B2 (en) * 2011-08-10 2018-07-24 Kobe Steel, Ltd. High-strength steel sheet excellent in seam weldability
US20130040165A1 (en) * 2011-08-10 2013-02-14 Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) High-strength steel sheet excellent in seam weldability
CN104204254A (en) * 2012-03-26 2014-12-10 株式会社神户制钢所 Boron-added high strength bolt steel having excellent delayed fracture resistance and high strength bolt
CN104204254B (en) * 2012-03-26 2016-06-22 株式会社神户制钢所 What delayed fracture resistance was excellent adds boron high-strength bolt steel and high-strength bolt
US9845519B2 (en) 2012-03-26 2017-12-19 Kobe Steel, Ltd. Boron-added high strength steel for bolt and high strength bolt having excellent delayed fracture resistance
US9982331B2 (en) 2012-09-19 2018-05-29 Jfe Steel Corporation Abrasion resistant steel plate having excellent low-temperature toughness and excellent corrosive wear resistance
WO2015194572A1 (en) * 2014-06-16 2015-12-23 株式会社神戸製鋼所 Ultra-high-strength steel sheet having excellent collision characteristics
JP2016003352A (en) * 2014-06-16 2016-01-12 株式会社神戸製鋼所 Ultrahigh-strength steel plate with excellent collision resistance
CN108603258A (en) * 2016-05-31 2018-09-28 新日铁住金株式会社 The high-strength steel sheet of excellent in low temperature toughness
CN107988553A (en) * 2017-11-28 2018-05-04 钢铁研究总院 A kind of high tenacity high speed axles steel and its heat treatment method

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