JP2015188920A - Manufacturing method of extremely thick steel plate - Google Patents
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 43
- 239000010959 steel Substances 0.000 title claims abstract description 43
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- 238000009749 continuous casting Methods 0.000 claims abstract description 18
- 239000000463 material Substances 0.000 claims abstract description 9
- 238000005242 forging Methods 0.000 claims description 53
- 229910052759 nickel Inorganic materials 0.000 claims description 2
- 238000005266 casting Methods 0.000 abstract description 7
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- 239000002994 raw material Substances 0.000 abstract description 6
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- 239000002184 metal Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
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- 238000009864 tensile test Methods 0.000 description 2
- 239000000956 alloy Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
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- 229910052748 manganese Inorganic materials 0.000 description 1
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本発明は、連続鋳造スラブを素材として用いた圧下比３未満の極厚鋼板について、強度、靭性および伸びに優れるとともに、表面性状も良好な極厚鋼板の製造方法である。 The present invention is a method for producing an extra-thick steel plate that is excellent in strength, toughness, and elongation, and also has good surface properties, for an extra-thick steel plate having a reduction ratio of less than 3 using a continuous cast slab as a raw material.
なお、本発明における極厚鋼板とは、製品板厚１００ｍｍ以上の厚鋼板をいう。 In addition, the very thick steel plate in the present invention refers to a thick steel plate having a product plate thickness of 100 mm or more.
極厚鋼板は、大形鋼塊を分塊圧延して製造した分塊スラブまたは溶鋼を連続鋳造して製造した連続鋳造スラブを素材として用いて厚板圧延することによって製造される。このうち、前者は押湯部の濃厚偏析部や鋼塊底部の負偏析部を切り捨てなければならないため歩留まりが低く、また、分塊圧延に伴うコストと時間が掛かるという問題があった。一方、後者の連続鋳造スラブによる方法はかかる問題はないものの、連続鋳造スラブの厚さに起因して鋳造後製品に至るまでの圧下率を大きくできず、そのため連続鋳造スラブ内に存在するセンターポロシティや偏析帯の圧下が行われ難いという問題があった。したがって、連続鋳造スラブを素材として製造された極厚鋼板については、内質不良となるものが多い。また、こうした事情から、従来、極厚鋼板の製造にあたっては、製品中心部の延性や靱性を要求される場合には圧下比（スラブ厚み／製品厚み）の下限を設け、それを下回るような場合には、分塊スラブを用いることとしていた。 The extra-thick steel plate is manufactured by rolling a thick slab produced by subjecting a large steel ingot to a thick rolling or a continuous cast slab produced by continuously casting a molten steel as a raw material. Among them, the former has a problem that the yield is low because the thick segregation part of the feeder part and the negative segregation part of the steel ingot bottom part must be discarded, and the cost and time associated with the ingot rolling are high. On the other hand, although the latter method using the continuous casting slab does not have such a problem, the reduction ratio until reaching the product after casting cannot be increased due to the thickness of the continuous casting slab. There is a problem that it is difficult to reduce the segregation zone. Therefore, there are many cases in which extremely thick steel plates manufactured using a continuously cast slab as a raw material have poor internal quality. In addition, due to such circumstances, in the past, when manufacturing ultra-thick steel sheets, when the ductility and toughness of the product center are required, a lower limit of the reduction ratio (slab thickness / product thickness) is provided, which is below that In order to do this, we decided to use a block slab.
しかし、分塊スラブを素材として用いる場合には、前述の理由によって製造コストが極めて高くなる。そのため、従来から連続鋳造スラブを素材として用いながら製造工程中にセンターポロシティを圧着させ、中心部における延性、靱性の高い極厚鋼板を得ようとする試みがなされていた。例えば、特許文献１では、鍛造金敷とスラブとの接触長（Ｂ）と、鍛造時のスラブ厚（Ｈ）について、Ｂ／Ｈ比が０．７〜１．０としてクロス鍛造を行うことにより、圧下比３未満での内質特性の優れた極厚鋼板が製造できることが開示されている。また、特許文献２では、全圧下率に対する鍛造圧下率との関係を特定することにより、内質特性の優れた極厚鋼板の製造方法が開示されている。
However, when a slab is used as a raw material, the manufacturing cost is extremely high for the reasons described above. For this reason, conventionally, attempts have been made to obtain a very thick steel plate having high ductility and toughness at the center by pressing the center porosity during the manufacturing process while using a continuous cast slab as a raw material. For example, in
一方で、強度や靭性を確保する目的で、連続鋳造スラブに合金元素としてＮｉを添加すると、加熱時に粒界に沿って酸化物が発生し、この酸化物が圧延後の表面割れにつながり、製品の表面疵になるという問題がある。このような表面疵については、特許文献１、２のいずれでも検討されていない。したがって、従来技術では、強度や靭性を確保しつつ、表面性状に優れた圧下比３未満の極厚鋼板を製造することは難しい。
On the other hand, when Ni is added as an alloying element to a continuously cast slab for the purpose of ensuring strength and toughness, an oxide is generated along the grain boundary during heating, and this oxide leads to surface cracks after rolling, resulting in a product. There is a problem of becoming a surface defect. Such surface flaws are not studied in any of
本発明は、上記実情に鑑みてなされたものであって、連続鋳造スラブを素材として用いた圧下比３未満の極厚鋼板について、強度、靭性および伸びに優れるとともに、表面性状も良好な極厚鋼板の製造方法を提供することを目的とする。 The present invention has been made in view of the above circumstances, and for an extremely thick steel plate having a reduction ratio of less than 3 using a continuous cast slab as a material, the thickness is excellent in strength, toughness and elongation, and also has excellent surface properties. It aims at providing the manufacturing method of a steel plate.
本発明者らは鋭意検討した結果、強度および靭性の確保を目的としてＮｉを添加しても、表面疵が発生せず、さらに伸びを確保できる極厚鋼板を得られるという知見を得た。本発明は、この知見に基づきなされたものであり、その要旨は以下の通りである。
［１］１．０〜４．０質量％のＮｉを含む鋼の連続鋳造スラブを、１２７０℃以上で５時間以上加熱保持した後、下金敷が上金敷より長い上下非対称の鍛造金敷により、前記連続鋳造スラブの両端部を幅方向から鍛造圧下し、次いで、前記上下非対称の鍛造金敷により、厚さ方向の鍛造圧下率を１パスあたり１０％以上とし、１パス目における鍛造方向長さを６００±５０ｍｍの範囲で前記連続鋳造スラブを厚さ方向から鍛造圧下し、その後、前記鍛造圧下により得られた鍛造材を厚板圧延することを特徴とする極厚鋼板の製造方法。
［２］前記連続鋳造スラブを厚さ方向から鍛造圧下する際に、２パス目以降の前記鍛造方向長さを、３００ｍｍ±５０ｍｍの範囲とすることを特徴とする［１］に記載の極厚鋼板の製造方法。
As a result of intensive studies, the present inventors have found that even when Ni is added for the purpose of securing strength and toughness, surface flaws do not occur, and an extra-thick steel plate that can secure elongation can be obtained. This invention is made | formed based on this knowledge, The summary is as follows.
[1] A continuous cast slab of steel containing 1.0 to 4.0 mass% Ni is heated and held at 1270 ° C. or higher for 5 hours or more, and then the lower anvil is longer than the upper anvil and the above-mentioned asymmetric forged anvil is used. Both ends of the continuous cast slab are forged and reduced from the width direction, and then the forging reduction rate in the thickness direction is set to 10% or more per pass by the asymmetric forging anvil, and the forging direction length in the first pass is 600. A method for producing an extra-thick steel plate, comprising subjecting the continuous cast slab to forging reduction in a thickness direction within a range of ± 50 mm, and then rolling the forging material obtained by the forging reduction.
[2] When the continuous cast slab is forged and reduced from the thickness direction, the length in the forging direction after the second pass is in the range of 300 mm ± 50 mm. A method of manufacturing a steel sheet.
本発明によれば、強度、靭性および伸びに優れるとともに、表面性状も良好な極厚鋼板を得ることができる。 According to the present invention, it is possible to obtain an ultra-thick steel plate that is excellent in strength, toughness, and elongation, and also has good surface properties.
以下、本発明の実施の形態を説明する。 Embodiments of the present invention will be described below.
本発明は、１．０〜４．０質量％のＮｉを含む連続鋳造スラブを、１２７０℃以上で５時間以上加熱保持した後、上下非対称の鍛造金敷により、前記連続鋳造スラブの端部を幅方向から鍛造圧下し、次いで、前記上下非対称の鍛造金敷により、スラブ厚さ方向の鍛造圧下率を１パスあたり１０％以上で、鍛造圧下の１パス目は前記連続鋳造スラブの端部と前記鍛造金型の上金敷との接触長を６００±５０ｍｍの範囲で前記連続鋳造スラブの端部を厚さ方向から鍛造圧下し、その後、前記鍛造圧下により得られる鍛造材を厚板圧延することを特徴とする。 In the present invention, a continuous cast slab containing 1.0 to 4.0% by mass of Ni is heated and held at 1270 ° C. or more for 5 hours or more, and then the end of the continuous cast slab is widened by an asymmetric forged anvil. Forging reduction is performed from the direction, and the forging reduction rate in the slab thickness direction is 10% or more per pass by the asymmetric forging anvil, and the first pass of forging reduction is the end of the continuous casting slab and the forging. The end of the continuous cast slab is forged and reduced from the thickness direction in a range of 600 ± 50 mm in contact length with the upper metal mold, and then the forged material obtained by the forging reduction is subjected to thick plate rolling. And
以下に、限定理由を説明する。 The reason for limitation will be described below.
１．０〜４．０質量％のＮｉを含む鋼の連続鋳造スラブ
鋼に１．０〜４．０質量％のＮｉを含有することにより、焼入れ性を向上し、板厚中心部（１／２位置）での靭性を確保することができる。
By containing 1.0 to 4.0% by mass of Ni in a continuously cast slab steel of steel containing 1.0 to 4.0% by mass of Ni, the hardenability is improved, and the thickness center portion (1 / Toughness at 2 position) can be secured.
なお、Ｎｉ以外の成分組成については特に限定されない。例えば、Ｃ：０．１０〜０．２０質量％、Ｓｉ：０．１５〜０．３５質量％、Ｍｎ：０．９５〜１．３０質量％、Ｐ：０．０２５質量％以下、Ｓ：０．０１０質量％以下、Ａｌ：０．０２〜０．０８質量％、Ｃｒ：０．５０〜１．５０質量％、Ｍｏ：０．４０〜０．６０質量％、Ｖ：０．０３〜０．０８質量％、Ｂ：０．０００５〜０．００１２質量％、を含有し、残部がＦｅおよび不可避的不純物からなる鋼、あるいは、上記成分組成に、さらに０．２５質量％以下のＣｕ、０．０５０質量％以下のＮｂ、０．０２５質量％以下のＴｉの１種以上を含む鋼を用いることができる。 The component composition other than Ni is not particularly limited. For example, C: 0.10 to 0.20 mass%, Si: 0.15 to 0.35 mass%, Mn: 0.95 to 1.30 mass%, P: 0.025 mass% or less, S: 0 0.010 mass% or less, Al: 0.02-0.08 mass%, Cr: 0.50-1.50 mass%, Mo: 0.40-0.60 mass%, V: 0.03-0. Steel containing 0.08 mass% and B: 0.0005-0.0012 mass% with the balance being Fe and unavoidable impurities, or the above component composition, and further 0.25 mass% or less of Cu, 0.0. A steel containing one or more of 050 mass% or less of Nb and 0.025 mass% or less of Ti can be used.
本発明では、鍛造圧下前に１２７０℃以上で５時間以上加熱保持することにより、合金元素に起因する表面疵の発生を防止することができる。強度および靭性向上を目的として、連続鋳造スラブに１．０質量％以上のＮｉを含有する鋼では、製造途中で表面疵が生じやすい。これは、連続鋳造スラブに１．０質量％以上のＮｉが含まれる鋼が加熱されると、粒界に沿ってＮｉ系酸化物が発生し、この酸化物が、表面からの深さ１〜５ｍｍに存在し、圧延後の表面割れにつながるためと考えられる。そこで、本発明においては、Ｎｉを含有した鋼の連続鋳造スラブを鍛造圧下前に、大気中（酸化雰囲気下）で、高温に加熱し、高温で５時間以上保持することにより、表層全面に酸化物を含むスケールを生成させる。このスケールを圧延前に除去することにより、圧延後の表面割れが生じず、結果として表面疵の発生を防止することができる。高温での加熱および高温保持後に、後述の鍛造圧下を行うことにより、粒界に沿った表層の疵を浅くすることができ、製品研磨による疵削除を可能とする。その結果、表面性状に優れた極厚鋼板を得ることができる。好ましくは、１２００℃以上、３時間以上である。 In the present invention, generation of surface flaws due to alloy elements can be prevented by heating and holding at 1270 ° C. or more for 5 hours or more before forging pressure reduction. For the purpose of improving strength and toughness, steel containing 1.0% by mass or more of Ni in a continuously cast slab is likely to cause surface defects during production. This is because when a steel containing 1.0 mass% or more of Ni is heated in a continuous cast slab, a Ni-based oxide is generated along the grain boundary, and this oxide has a depth of 1 to It is considered that it exists at 5 mm and leads to surface cracks after rolling. Therefore, in the present invention, the continuous casting slab of steel containing Ni is heated to a high temperature in the atmosphere (under an oxidizing atmosphere) before forging pressure, and is maintained at a high temperature for 5 hours or more to oxidize the entire surface layer. Generate a scale containing objects. By removing this scale before rolling, surface cracks after rolling do not occur, and as a result, generation of surface flaws can be prevented. By performing forging reduction described later after heating at high temperature and holding the high temperature, the surface wrinkles along the grain boundaries can be made shallower, and the wrinkles can be removed by product polishing. As a result, it is possible to obtain a very thick steel plate having excellent surface properties. Preferably, it is 1200 ° C. or more and 3 hours or more.
下金敷が上金敷より長い上下非対称の鍛造金敷により、前記連続鋳造スラブの両端部を幅方向から鍛造圧下
前述したように、鍛造圧下前にＮｉを含有する鋼の連続鋳造スラブを高温で加熱保持することにより、スケールが生成する。このスケールは、厚み方向の鍛造圧下の前に行われる連続鋳造スラブの幅方向からの鍛造圧下により、容易に破壊、剥離される（図１参照）。なお、この際、スプレー水を噴射してスケールを吹き飛ばしても良い。したがって、圧延前に、表面疵に起因する酸化物などのスケールを除去することができる。その結果、表面疵の発生を防止することができる。
なお、鍛造金敷の長さについては、３００ｍｍ以上であればよい。
Forging down the both ends of the continuous casting slab from the width direction by using an asymmetric forging anvil where the lower anvil is longer than the upper anvil. As described above, the continuous casting slab of steel containing Ni is heated and held at a high temperature before forging reduction. By doing so, a scale is generated. This scale is easily broken and peeled off by forging pressure from the width direction of the continuously cast slab, which is performed before forging pressure in the thickness direction (see FIG. 1). At this time, the scale may be blown off by spraying spray water. Therefore, before rolling, scales such as oxides caused by surface defects can be removed. As a result, generation of surface flaws can be prevented.
In addition, about the length of a forge anvil, what is necessary is just 300 mm or more.
前記上下非対称の鍛造金敷により、厚さ方向の鍛造圧下率を１パスあたり１０％以上とし、１パス目における鍛造方向長さを６００±５０ｍｍの範囲で前記連続鋳造スラブを厚さ方向から鍛造圧下
上下非対称の鍛造金敷を用いた被鍛造物の内質改善効果は、上下対称に圧下した場合に生じるスラブ厚中心位置の引張応力を、意図的にスラブ厚方向へずらし、中心位置の静水圧が大きくなる事を利用したＦＭ（Ｆｒｅｅ ｆｒｏｍ Ｍａｎｎｅｓｍａｎｎ ｅｆｆｅｃｔ）鍛造法として、一般的に知られている。本発明においては、上下非対称の鍛造金敷を用いて、スラブ厚さ方向の鍛造圧下率を１パスあたり１０％以上で鍛造圧下を行うことにより、スラブ厚方向の内質改善作用を高め、センターポロシティの完全消滅を達成することができる。その結果、内質特性が改善し、得られる極厚鋼板について、所望の伸びが得られる。
鍛造圧下の１パス目について、連続鋳造スラブの端部と鍛造金型の上金敷との接触長さである鍛造方向長さを６００±５０ｍｍの範囲とすることにより、端部の内質特性が改善する。図２（ａ）に示すように、鍛造方向長さＸが、６００±５０ｍｍの範囲であればよい。連続鋳造スラブの端部の内質特性が改善する理由は、以下のように考えられる。
With the asymmetric forged anvil, the forging reduction rate in the thickness direction is 10% or more per pass, and the continuous casting slab is reduced from the thickness direction in the forging direction length in the range of 600 ± 50 mm in the first pass. The effect of improving the inner quality of the forged object using an asymmetric forged anvil is that the tensile stress at the center position of the slab thickness that is generated when it is rolled down symmetrically is intentionally shifted in the slab thickness direction, and the hydrostatic pressure at the center position is reduced. It is generally known as an FM (Free from Mannesmann effect) forging method utilizing the increase in size. In the present invention, the forging reduction in the slab thickness direction is performed at a forging reduction rate of 10% or more per pass using an asymmetric forging anvil, thereby improving the inner quality improvement effect in the slab thickness direction. Can be completely eliminated. As a result, the internal properties are improved, and a desired elongation can be obtained for the obtained extra-thick steel plate.
For the first pass under forging pressure, by setting the length in the forging direction, which is the contact length between the end of the continuous casting slab and the upper metal plate of the forging die, in the range of 600 ± 50 mm, the internal quality characteristics of the end can be improved. Improve. As shown to Fig.2 (a), the forge direction length X should just be the range of 600 +/- 50mm. The reason why the internal quality characteristics of the end portion of the continuously cast slab are improved is considered as follows.
連続鋳造スラブの端部は、鍛造の際に自由端となるので、板厚中心部（１／２ｔ位置、ｔ：板厚）に塑性歪が集中しない。このため、連続鋳造スラブの内部よりも大きな接触長とすることにより、被鍛造材に対する上面および下面からの拘束を大きくして、塑性歪を板厚中心部（１／２ｔ位置）に集中させることにより、板厚中心部（１／２ｔ位置）のセンターポロシティがなくなる。 Since the end of the continuously cast slab becomes a free end during forging, plastic strain does not concentrate at the center of the plate thickness (1 / 2t position, t: plate thickness). For this reason, by making the contact length larger than the inside of the continuous casting slab, the restraint from the upper surface and the lower surface on the material to be forged is increased, and the plastic strain is concentrated at the thickness center portion (1 / 2t position). As a result, the center porosity at the center of the plate thickness (1 / 2t position) is eliminated.
また、鍛造圧下の２パス目以降は、図２の（ｂ）に示すように、鍛造方向長さＸが、３００ｍｍ±５０ｍｍの範囲であることが好ましい。３００ｍｍ±５０ｍｍの範囲にすることにより、スラブ厚と同等の長さ以上となり、板厚中心にも歪を加えることができる。 Also, after the second pass under forging pressure, as shown in FIG. 2B, the forging direction length X is preferably in the range of 300 mm ± 50 mm. By setting it in the range of 300 mm ± 50 mm, the length becomes equal to or longer than the slab thickness, and distortion can be applied to the center of the plate thickness.
鍛造圧下により得られた鍛造材を厚板圧延する
次に、鍛造圧下により得られた鍛造材を厚板圧延する。厚板圧延の条件としては特に限定されず、常法に従って、目的とする板厚まで圧延すればよい。
Next, the forging material obtained by forging reduction is thick-rolled. Next, the forging material obtained by forging reduction is thick-rolled. The conditions for thick plate rolling are not particularly limited, and may be rolled to a target plate thickness according to a conventional method.
以上により、圧下比が３未満であっても、強度、靭性および伸びに優れるとともに表面性状にも優れた極厚鋼板を得ることができる。 As described above, even if the rolling ratio is less than 3, it is possible to obtain an extra-thick steel plate that is excellent in strength, toughness, and elongation, and also excellent in surface properties.
厚さ３１０ｍｍの連続鋳造スラブを、昇温速度３０℃／ｈで１２７０℃に加熱し、３００分保持した後、鍛造圧下し、得られた２５０ｍｍの厚さの鍛造材を、圧下量１００ｍｍ、圧下率４０％で１５０ｍｍの板厚に厚板圧延することにより、板厚１５０ｍｍの極厚鋼板を得た。連続鋳造スラブの組成を表１に、鍛造圧下条件を表２にそれぞれ示す。 A continuously cast slab having a thickness of 310 mm was heated to 1270 ° C. at a heating rate of 30 ° C./h, held for 300 minutes, and then forged and the resulting forged material having a thickness of 250 mm was reduced by a reduction amount of 100 mm. An extra-thick steel plate having a plate thickness of 150 mm was obtained by rolling the plate to a plate thickness of 150 mm at a rate of 40%. Table 1 shows the composition of the continuously cast slab, and Table 2 shows the forging reduction conditions.
得られた極厚鋼板全てについて、板厚中心部（１／２ｔ位置）について、引張試験、靭性評価および表面性状評価を行った。
引張試験については、板厚中心部（１／２ｔ位置）から採取したサンプルについて、５６０℃×８ｈの試験片熱処理後、板厚中心位置に対しＣ方向（板厚方向と圧延方向の双方に直角な方向）の引張試験（ＪＩＳ Ｚ２２４１）を行い、強度および伸びを評価した。引張強度（ＴＳ）：７７０ＭＰａ以上、降伏強度（ＹＳ）：６９０ＭＰａ以上、伸び（Ｅｌ）：１６％以上を合格とした。
About all the obtained very thick steel plates, the tension test, toughness evaluation, and surface property evaluation were performed about the plate | board thickness center part (1 / 2t position).
For the tensile test, a sample taken from the center of the plate thickness (1/2 t position) was subjected to heat treatment of the specimen at 560 ° C. × 8 h, and then C direction (perpendicular to both the plate thickness direction and the rolling direction) with respect to the plate thickness center position. ), A tensile test (JIS Z2241) was conducted to evaluate strength and elongation. Tensile strength (TS): 770 MPa or more, yield strength (YS): 690 MPa or more, and elongation (El): 16% or more were accepted.
靭性については、板厚中心部（１／２ｔ位置）から採取した試験片（ＪＩＳ Ｚ２２４２）を用いたシャルピー衝撃試験によって得られる、−４０℃における吸収エネルギー（ｖＥ−４０）で評価した。また、内質評価としてＪＩＳ Ｇ ０８０１に準拠した超音波探傷試験も行った。−４０℃でのシャルピー衝撃試験値ｖＥ−４０：３４Ｊ以上、内質評価：軽きず以下（軽きず：２５％＜きずエコー高さ≦５０％）を合格とした。 The toughness obtained by Charpy impact test using test pieces taken from the center of plate thickness (1 / 2t position) a (JIS Z2242), was evaluated by absorbed energy at -40 ℃ (v E -40). In addition, an ultrasonic flaw detection test based on JIS G 0801 was also performed as an internal quality evaluation. Charpy impact test value at −40 ° C. v E −40 : 34 J or more, internal quality evaluation: light flaws or less (light flaws: 25% <flaw echo height ≦ 50%) was accepted.
また、表面性状については、グラインダー手入れを実施したあと、鋼板の表面を目視で観察し、疵がなかったものを合格とした。 Moreover, about surface property, after implementing grinder care, the surface of the steel plate was observed visually and the thing without a wrinkle was set as the pass.
得られた評価結果を表３に示す。 The obtained evaluation results are shown in Table 3.
表３の結果から、本発明例（Ｎｏ．１、４）はいずれも、強度、伸び、靭性、表面性状に優れている。一方、比較例（Ｎｏ．２）は、１パス目鍛造長さが短かったためにポロシティが残存して伸び低値が発生した。比較例（Ｎｏ．３）は、鍛造を行わなかったために初期のポロシティが残存して伸び低値が発生し、内質評価も不合格であった。また、表面疵も残存し、表面性状も不合格となった。比較例（Ｎｏ．５）は、Ｎｉ添加量が少なかったため、靭性低値により不合格となった。 From the results of Table 3, all of the inventive examples (No. 1, 4) are excellent in strength, elongation, toughness, and surface properties. On the other hand, in the comparative example (No. 2), since the forging length in the first pass was short, the porosity remained and a low elongation value occurred. In the comparative example (No. 3), since no forging was performed, the initial porosity remained, a low elongation value was generated, and the internal quality evaluation was also unacceptable. Further, surface defects remained and the surface properties were also rejected. In Comparative Example (No. 5), since the amount of Ni added was small, it was rejected due to the low toughness value.
１ 連続鋳造スラブ
２ 鍛造金敷の上金敷
３ 鍛造金敷の下金敷
Ｘ 接触長さ
1
Claims (2)
下金敷が上金敷より長い上下非対称の鍛造金敷により、前記連続鋳造スラブの両端部を幅方向から鍛造圧下し、
次いで、前記上下非対称の鍛造金敷により、厚さ方向の鍛造圧下率を１パスあたり１０％以上とし、１パス目における鍛造方向長さを６００±５０ｍｍの範囲で前記連続鋳造スラブを厚さ方向から鍛造圧下し、
その後、前記鍛造圧下により得られた鍛造材を厚板圧延することを特徴とする極厚鋼板の製造方法。 After continuously holding a continuous cast slab of steel containing 1.0 to 4.0 mass% Ni at 1270 ° C. or more for 5 hours or more,
Forging down the both ends of the continuous cast slab from the width direction by using an asymmetric forged anvil with a lower anvil that is longer than the upper anvil,
Next, with the asymmetric forged anvil, the forging reduction rate in the thickness direction is 10% or more per pass, and the continuous casting slab is removed from the thickness direction in the forging direction length in the first pass in the range of 600 ± 50 mm. Forging down,
Then, the forging material obtained by the said forging reduction is thick-rolled, The manufacturing method of the extra-thick steel plate characterized by the above-mentioned.
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| JP2006263730A (en) * | 2005-03-22 | 2006-10-05 | Jfe Steel Kk | Method for manufacturing extra-heavy steel plate very excellent in internal-quality characteristics |
| JP2009248112A (en) * | 2008-04-03 | 2009-10-29 | Sumitomo Metal Ind Ltd | Method for producing billet |
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