JP3709108B2 - Steel plate with small deformation or variation in processing during welding or curved surface processing and manufacturing method thereof - Google Patents
Steel plate with small deformation or variation in processing during welding or curved surface processing and manufacturing method thereof Download PDFInfo
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Description
【0001】
【発明の属する技術分野】
本発明は、溶接時や曲面加工時に生じる変形または加工のばらつきを極力低減することのできる鋼板、およびその様な鋼板を製造するための有用な方法に関するものである。
【0002】
【従来の技術】
造船、建築、橋梁等の素材としての鋼板は、溶接や曲面加工が施されるが、こうした溶接や曲面加工が行われる設備では、人手を省いたり生産効率の向上を図るという観点から、自動化や合理化が進められている。こうした設備において、溶接や曲面加工を行なう際には、予め予想若しくは設定した変形量または加工量と実際の変形量または加工量に差異が生じると、人による手直しが必要となって生産性が著しく悪化し、自動化・合理化という所期の目的を達成することができなくなる。
【0003】
例えば、鋼板を溶接した際には、溶接入熱によって板面内で縦収縮や横収縮、或いは面外への角変形等の変形が発生する。また、船の先後端部やタンク等で見られる曲面は、プレス等の機械的手段や熱的手段(例えば、線状加熱)によって加工されるが、こうした場合にも加工量が予想を外れることがある。
【0004】
鋼板の溶接時の変形量や曲面加工時における加工量δは、鋼板特性βと溶接・加工条件γとからδ=(β,γ)なる関係で決定されるとされている。そして、鋼板特性についてはJIS等の夫々の鋼板の規格や仕様により規定されている。しかしながら、従来では同一の規格の鋼板を同一の条件で溶接或は曲面加工しても、変形量若しくは加工量が異なって(即ち、ばらつきが生じて)、手入れが必要となるという問題があった。
【0005】
【発明が解決しようとする課題】
本発明はこうした状況の下でなされたものであって、その目的は、溶接時や曲面加工時における変形または加工ばらつきを極力低減し、その後の手入れを不要にした鋼板、およびその様な鋼板を製造する為の有用な方法を提供することにある。
【0006】
【課題を解決するための手段】
上記目的を達成し得た本発明の鋼板とは、圧延方向の降伏応力σLと幅方向の降伏応力σCとが下記(1)式の関係を満足する点に要旨を有するものである。
2×|σL−σC|/(σL+σC)≦α ……(1)
但し、αは必要な加工精度によって予め決まる値であり、鋼板の厚みが40mm以下のときには0.03であり、鋼板の厚みが40mmを超えるときには0.05である。
【0009】
上記の様な本発明の鋼板を製造するに当たっては、圧延方向の降伏応力σLと幅方向の降伏応力σCとを比較してその値が小さい方向を矯正方向とし、この方向に沿ってローラレベラによって矯正することによって前記(1)式の関係を満足する様にすれば良い。
【0010】
またこの製造方法においては、下記(2)式の関係を満足する様にして矯正することが好ましい。
ε=|σL−σC|×b ……(2)
但し、εは矯正中に鋼板表面に導入される塑性歪みの絶対値、bは鋼種によ
って決まる値を夫々示す。
【0011】
【発明の実施の形態】
鋼板特性の中で降伏応力については、一般に夫々の鋼板の規格或は鋼板仕様に応じて、圧延された延べ板の板幅方向または板長さ方向のいずれか一方から採取したテストピース(試験片)による引張試験によって測定されて保証値とされる(例えば、炭素鋼や低合金鋼では、JIS G 0303「鋼材の検査通則」)。
【0012】
一般的に、鋼板のL方向、即ち圧延された延べ板の圧延方向から採取されたテストピースと、上記C方向から採取されたテストピースでは、引張試験による降伏応力に差異があることが知られている。尚、L方向から採取されたテストピ−スとは、その軸芯方向(長手方向)がL方向となる様に採取されたテストピースであり、C方向から採取されたテストピ−スとは、その軸芯方向がC方向となる様に採取されたテストピースのことである。
【0013】
しかしながら、従来では、鋼板のL方向とC方向の降伏応力の関係については明らかにされているとはいえず、またそれらが溶接時や曲面加工時の変形量または加工量に及ぼす影響についても全く不明であった。
【0014】
本発明者らは、(1)鋼板のL方向とC方向の降伏応力の関係や、(2)それらが溶接や曲面加工時の変形や加工に及ぼす影響等について、様々な角度から検討した。その結果、次の様な事実が明らかになった。尚、溶接時の場合を「変形」、曲面加工時の場合を「加工」と呼ぶのが一般的であるが、以下の説明では説明の便宜上、曲面加工時の加工量をも「変形量」と呼ぶことがある。また、本発明における変形とは、前述した縦収縮や横収縮(後記実施例2参照)、或は面外への角度変形をも含む趣旨である。
【0015】
まず、採取された方向によって(L方向またはC方向)、テストピースでの引張試験結果の異なる鋼板を用いて曲面加工を行った場合に、曲げ方向をL方向としたときとC方向としたときとでは、変形量(加工量)に差異が生じることが分かった。こうした状態を図面によって説明する。
【0016】
図1は、線状加熱による曲面加工を行なった場合の変形量を測定する状態を示す概略説明図である。図1に示す様に、長さ1mの鋼板1を用いその中央部で幅方向にそって線状加熱を行って曲面加工を行ない[図1(a):曲げ方向は長さ方向]、採取された方向によって(L方向またはC方向)テストピースでの引張試験結果の異なる鋼板における変形量[図1(b)]を測定した。
【0017】
その結果(曲げ方向と変形量の関係)を、図2に示す。尚、図2における曲げ方向とは前述の如く長さ方向を意味し、例えば「曲げ方向がC方向」とは鋼板の長さ方向がC方向(従って、線状加熱方向はL方向)であることを意味する。
【0018】
図2から明らかな様に、曲げ方向をC方向となる様にして曲面加工したときの方が、曲げ方向をL方向となる様にして曲面加工したときよりも変形量が大きくなっていることが分かる。この様な方向による差異は、溶接時の縦収縮、横収縮、角変形等についても生じることも分かった。
【0019】
また、C方向から採取されたテストピースでの引張試験結果が同じ鋼板であっても、L方向から採取されたテストピースでの引張試験結果には鋼板毎に差異が認められ、且つ溶接方向や線状加熱による曲げ方向をL方向とした場合の変形量に差異が見られることも分かった。
【0020】
図3は、C方向から採取されたテストピースの引張試験において降伏応力(C方向降伏応力)が410N/mm2である鋼板について、L方向から採取したテストピースの引張試験における降伏応力(L方向降伏応力)と、曲げ方向がL方向とした場合の変形量との関係を示したグラフである。この結果から明らかな様に、C方向降伏応力が一定の鋼板であっても、L方向降伏応力に差異が認められ、且つ曲げ方向をL方向とした場合の変形量に差異が見られることが分かる。
【0021】
以上の事実から、溶接時や曲面加工時において問題となる変形ばらつき(または加工ばらつき)は、鋼板におけるL方向とC方向での降伏応力の差異が原因で生じることが明らかとなった。そこで本発明者らは、鋼板におけるL方向とC方向での降伏応力の差異をできるだけなくして均一化すれば、変形ばらつきの発生が防止できるとの着想の下で更に鋭意研究した。その結果、圧延方向(L方向)の降伏応力σLと幅方向(C方向)の降伏応力σCとが下記(1)式の関係を満足する様にすれば、上記目的が見事に達成されることを見出し、本発明を完成した。
2×|σL−σC|/(σL+σC)≦α ……(1)
但し、αは必要な加工精度によって予め決まる値。
【0022】
尚、上記(1)式において、(σL−σC)の項を絶対値で表したのは、L方向の降伏応力σLがC方向の降伏応力σCよりも必ずしも大きな値となるとは限らず、その逆の場合も有り得るので(前記図3参照)、降伏応力の差として|σL−σC|を採用したものである。
【0023】
上記(1)式におけるαは、溶接や曲面加工の実績から予め決定することも可能であるが、目標とする変形量をF、許容される変形または加工量からのずれ量をdとしたとき、これらの比(d/F)でαを表わすこともできる。この様にαを設定した場合には、変形ばらつきが全てσLとσCの差に起因するとして評価できるので、変形ばらつきがより高精度に評価されて確実に必要な精度が得られることになる。即ち、変形ばらつきの要因には、σLとσC以外に加熱条件のばらつき等もあるが、それら他の要因による変形ばらつきを仮にσLとσCの差に起因するとしてσLとσCの差を厳密に決めることによって、仮に加熱条件等にばらつきがあったとしても、変形量を許容されるばらつきの範囲内に抑えることが可能となる。
【0024】
例えば、船体に使用される厚みが40mm以下の鋼板においては、目標とされる変形量(または加工量)が100mmであるとして、この加工量から許容されるずれ量が3mmであり、こうしたずれ量は厚みが40mm以下の鋼板一般に当てはまるものであるので、このときにはα=0.03と予め設定しておけば、殆どの溶接・曲面加工において十分な精度が確実に得られることになる。
【0025】
一方、板厚が増大すると、溶接時や曲面加工時の入熱が大きくなるので、圧延方向の降伏応力σLとそれと板面内で直交する方向の降伏応力σCの差の影響がなくなるので、板厚が40mmを超える鋼板で必要となるαの値は、薄板の場合と比べて大きく設定でき、例えばα=0.05とすれば殆どの溶接・曲面加工において十分な精度が確実に得られることになる。
【0026】
次に、本発明の製造方法について説明する。まず、前記L方向とC方向で採取されたテストピースでの引張試験で得られる降伏応力の差異は、熱間圧延時の温度と圧下量の微妙な差異によって生じるものと思われる。しかしながら、現状では、熱間圧延における温度や圧下量によって圧延後におけるL方向若しくはC方向の降伏応力を同時に制御する技術は皆無であり、従来の圧延法においては前記(1)式を満足する鋼板を得ることはできなかった。
【0027】
本発明者らが、上記の様な鋼板を実現する方法について検討した結果、ローラレベラでの冷間矯正を活用すれば、上記(1)式を満足する鋼板が製造できたのである。本発明方法における製造原理は、次の通りである。
【0028】
鋼板を冷間で矯正した際には、主に矯正方向に塑性歪みが導入される。その矯正方向に導入された塑性歪みにより、鋼板は加工硬化し、且つその上昇度合いは板面内での矯正方向によっても異なる。本発明者らは、こうした効果が、加工例として線状加熱による曲面加工への影響について調査した。その結果を図4に示す。
【0029】
即ち、図4は、曲げ方向による変形量の違いに対して矯正が与える影響を示したグラフであるが、矯正前(矯正無し)の鋼板ではL方向とC方向では変形量に差異が見られるが、矯正後(矯正有り)の鋼板ではその差がほぼ無くなっていることが分かる。
【0030】
本発明方法は、こうした性質を利用したものであり、具体的には、圧延方向の降伏応力σLと幅方向の降伏応力σCを比較してその値が小さい方向を矯正方向とし、この方向に沿ってローラレベラによって矯正して、σLとσCの差を制御することによっ溶接時や曲面加工時の変形のばらつきを解消するものである。
【0031】
また、上記方法の矯正を行なうに当たっては、σLとσCの差に応じてその差を解消するだけの塑性歪みを導入すれば良い。具体的には、下記(2)式の関係を満足する様にして矯正すれば、σLとσCの差を確実に制御でき、その結果として変形ばらつきを防止することが可能となる。その際の矯正条件と導入される表面歪みの関係は、種々の文献(例えば、「矯正加工」、日本塑性加工学会編)に記載されている方法によって容易に算定できる。
ε=|σL−σC|×b ……(2)
但し、εは矯正中に鋼板表面に導入される塑性歪みの絶対値、bは鋼種によ
って決まる値を夫々示す。
【0032】
例えば、係数bは鋼種に応じて引張試験等により測定される鋼板の加工硬化係数Hを基に求めることができる[下記(3)式]。
b=m×1/H ……(3)
ここで、係数mは種々の鋼板での矯正前後におけるσLおよびσCと加工硬化係数の測定結果から予め決めておけば良い。
【0033】
例えば、低炭素鋼の場合、鋼種に応じて降伏応力の単位をkgf/mm2とすると、b=0.01〜0.025程度の値となる。
【0034】
尚、本発明で対象とする鋼板の種類については、特に限定するものではなく、例えば炭素鋼、低合金鋼、ボイラ用鋼、圧力容器用鋼、等各種の鋼板が挙げられる。
【0035】
以下、本発明を実施例によって更に詳細に説明するが、下記実施例は本発明を限定する性質のものではなく、前・後記の趣旨に特徴して設計変更することはいずれも本発明の技術的範囲に含まれるものである。
【0036】
【実施例】
実施例1
本発明で規定する要件[前記(1)式]を満足する鋼板(本発明材)と満足しない鋼板(比較材)を準備し、これらの鋼板に対して同一の条件で線状加熱による曲面加工した場合の目標加工量からの変形ばらつき度合いを調査した。このときの、「対象材と加工要領」は下記の通りであり、各鋼板における前記(1)式の左辺[2×|σL−σC|/(σL+σC)]の値は下記表1に示す通りである。尚、このときの線状加熱位置の状態を図5[図5(a)は平面図、図5(b)はA−B線矢視断面図]に示す。
【0037】
【0038】
【表1】
【0039】
その結果を(曲がり量の目標値からのずれ量)、下記表2に示すが、比較材では許容量を超える目標加工量からの変形ばらつきが発生しているのに対し、本発明材では全てが許容範囲内に入っていることが分かる。
【0040】
【表2】
【0041】
実施例2
C方向の降伏応力が同一の鋼板について、本発明による冷間矯正した鋼板(本発明材)と施さない鋼板(比較材)を準備し、これらの鋼板に対して溶接線を板長手方向(L方向)として板継ぎ溶接を行ない、設定した板収縮量からの収縮ばらつき度合いを調査した。このときの、「対象材と溶接要領」は下記の通りであり、矯正前の各鋼板における前記(1)式の左辺[2×|σL−σC|/(σL+σC)]の値は下記表3に示す通りである。尚、このときの溶接位置の状態を図6に示す。
【0042】
〈対象材と溶接要領〉
鋼板の種類 :500N/mm2級鋼板
鋼板サイズ :板厚16mm、板幅2500mm、板長さ2500mm
溶接位置 :図6
溶接条件 :サブマージ溶接(電流460A,電圧32V,溶接速度0.43m/分、3パス
必要加工精度:設定収縮量=5mm、許容収縮ばらつき=0.5mm
【0043】
【表3】
【0044】
表3のNo.1〜3の鋼板のうち、本発明例については、L方向を矯正方向として下記表4に示す条件にて冷間矯正を適用し、比較材では矯正なしで溶接を実施した。
【0045】
【表4】
【0046】
その結果を(収縮量の設定値からのずれ量)、下記表5に示すが、比較材では許容量を超える設定収縮量からの収縮ばらつきが発生しているのに対し、本発明材では全て許容範囲内に入っていることが分かる。
【0047】
【表5】
【0048】
【発明の効果】
本発明は以上の様に構成されており、溶接時や曲面加工時における変形または加工ばらつきを極力低減し、その後の手入れを不要にした鋼板が実現できた。
【図面の簡単な説明】
【図1】線状加熱による曲面加工を行なった場合の変形量を測定する状態を示す概略説明図である。
【図2】鋼板の曲げ方向と変形量の関係を示すグラフである。
【図3】C方向降伏応力が410N/mm2である鋼板について、L方向降伏応力と、曲げ方向がL方向とした場合の変形量との関係を示したグラフである。
【図4】曲げ方向による変形量の違いに対して矯正が与える影響を示したグラフである。
【図5】実施例1における線状加熱位置の状態を示す説明図である。
【図6】実施例2における溶接位置の状態を示す説明図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a steel plate capable of reducing deformation or processing variation that occurs during welding or curved surface processing as much as possible, and a useful method for manufacturing such a steel plate.
[0002]
[Prior art]
Steel plates as materials for shipbuilding, construction, bridges, etc. are subjected to welding and curved surface processing, but in equipment where such welding and curved surface processing are performed, from the viewpoint of saving labor and improving production efficiency, Streamlining is underway. In such equipment, when welding or curved surface processing is performed, if there is a difference between the deformation amount or processing amount that is predicted or set in advance and the actual deformation amount or processing amount, human modifications are required and productivity is significantly increased. It becomes worse and the intended purpose of automation and rationalization cannot be achieved.
[0003]
For example, when a steel sheet is welded, deformation such as longitudinal shrinkage, lateral shrinkage, or out-of-plane angular deformation occurs due to welding heat input. In addition, the curved surface seen at the front and rear ends of the ship and tanks is processed by mechanical means such as a press or thermal means (for example, linear heating). There is.
[0004]
It is said that the deformation amount during welding of a steel plate and the processing amount δ during curved surface processing are determined by a relationship of δ = (β, γ) from the steel plate characteristic β and the welding / processing condition γ. And about the steel plate characteristic, it is prescribed | regulated by the specification and specification of each steel plate, such as JIS. However, there has been a problem that, even if the same standard steel plate is welded or curved surface processed under the same conditions, the amount of deformation or the amount of processing is different (that is, variation occurs) and maintenance is required. .
[0005]
[Problems to be solved by the invention]
The present invention has been made under such circumstances, and the object thereof is to provide a steel plate that reduces deformation or processing variation as much as possible during welding or curved surface processing and eliminates the need for subsequent maintenance, and such a steel plate. It is to provide a useful method for manufacturing.
[0006]
[Means for Solving the Problems]
The steel sheet of the present invention that has achieved the above object has a gist in that the yield stress σL in the rolling direction and the yield stress σC in the width direction satisfy the relationship of the following expression (1).
2 × | σL−σC | / (σL + σC) ≦ α (1)
However, α is a value determined in advance by the required processing accuracy, and is 0.03 when the thickness of the steel plate is 40 mm or less, and 0.05 when the thickness of the steel plate exceeds 40 mm.
[0009]
In producing the steel sheet of the present invention as described above, the yield stress σL in the rolling direction and the yield stress σC in the width direction are compared, and the direction in which the value is small is defined as the correction direction, and correction is performed along this direction by the roller leveler. By doing so, the relationship of the formula (1) may be satisfied.
[0010]
Moreover, in this manufacturing method, it is preferable to correct | amend so that the relationship of following (2) Formula may be satisfied.
ε = | σL−σC | × b (2)
However, (epsilon) shows the absolute value of the plastic distortion introduce | transduced on the steel plate surface during correction | amendment, b shows the value decided by steel grade, respectively.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Among the steel sheet characteristics, the yield stress is generally determined by test pieces (test specimens) taken from either the sheet width direction or the sheet length direction of the rolled plate according to the standard or sheet specifications of each sheet. ) And a guaranteed value (for example, in the case of carbon steel and low alloy steel, JIS G 0303 “General Inspection Rules for Steel”).
[0012]
Generally, it is known that there is a difference in yield stress between a test piece taken from the L direction of a steel plate, that is, a rolling direction of a rolled plate and a test piece taken from the C direction. ing. The test piece sampled from the L direction is a test piece sampled so that its axial direction (longitudinal direction) is the L direction, and the test piece sampled from the C direction is It is a test piece collected so that the axial direction is the C direction.
[0013]
However, conventionally, it cannot be said that the relationship between the yield stress in the L direction and the C direction of the steel sheet has been clarified, and the influence on the deformation amount or processing amount at the time of welding or curved surface processing is not at all. It was unknown.
[0014]
The present inventors examined (1) the relationship between the yield stress in the L direction and the C direction of the steel sheet, and (2) the influence of these on deformation and processing during welding and curved surface processing from various angles. As a result, the following facts became clear. In general, the case of welding is referred to as “deformation”, and the case of curved surface processing is referred to as “processing”. However, in the following description, the processing amount during curved surface processing is also referred to as “deformation amount” for convenience of explanation. Sometimes called. Moreover, the deformation | transformation in this invention is the meaning including the vertical deformation | transformation and lateral contraction (refer Example 2 mentioned later) mentioned above, or the angular deformation to an out-of-plane.
[0015]
First, when curved surface processing is performed using steel plates with different tensile test results on the test piece depending on the sampled direction (L direction or C direction), when the bending direction is the L direction and the C direction It was found that there was a difference in the amount of deformation (processing amount). Such a state will be described with reference to the drawings.
[0016]
FIG. 1 is a schematic explanatory view showing a state in which the amount of deformation is measured when curved surface processing is performed by linear heating. As shown in FIG. 1, a
[0017]
The result (relationship between bending direction and deformation amount) is shown in FIG. Note that the bending direction in FIG. 2 means the length direction as described above. For example, “the bending direction is the C direction” means that the length direction of the steel sheet is the C direction (therefore, the linear heating direction is the L direction). Means that.
[0018]
As is clear from FIG. 2, the amount of deformation is larger when the curved surface is processed with the bending direction being the C direction than when the curved surface is processed with the bending direction being the L direction. I understand. It was also found that such a difference due to the direction also occurs with respect to longitudinal shrinkage, lateral shrinkage, angular deformation, and the like during welding.
[0019]
Moreover, even if the tensile test result with the test piece taken from the C direction is the same steel plate, the tensile test result with the test piece taken from the L direction shows a difference for each steel plate, and the welding direction and It was also found that there is a difference in the amount of deformation when the bending direction by linear heating is the L direction.
[0020]
FIG. 3 shows the yield stress (L direction) in the tensile test of a test piece taken from the L direction for a steel sheet whose yield stress (C direction yield stress) is 410 N / mm 2 in the tensile test of the test piece taken from the C direction. It is the graph which showed the relationship between the amount of deformation | transformation when a bending direction is made into the L direction. As is clear from this result, even if the steel plate has a constant C-direction yield stress, a difference is observed in the L-direction yield stress, and there is a difference in the amount of deformation when the bending direction is the L-direction. I understand.
[0021]
From the above facts, it became clear that deformation variation (or processing variation), which is a problem during welding or curved surface processing, is caused by a difference in yield stress between the L direction and the C direction in the steel sheet. Accordingly, the present inventors have further studied earnestly under the idea that the occurrence of variation in deformation can be prevented if the difference in yield stress between the L direction and the C direction in the steel sheet is minimized and made uniform. As a result, if the yield stress σL in the rolling direction (L direction) and the yield stress σC in the width direction (C direction) satisfy the relationship of the following equation (1), the above object can be achieved brilliantly. The present invention has been completed.
2 × | σL−σC | / (σL + σC) ≦ α (1)
However, α is a value determined in advance depending on the required processing accuracy.
[0022]
In the above equation (1), the term (σL−σC) is expressed as an absolute value because the yield stress σL in the L direction is not necessarily larger than the yield stress σC in the C direction. Since the reverse case is also possible (see FIG. 3), | σL−σC | is adopted as the difference in yield stress.
[0023]
Α in the above equation (1) can be determined in advance from the results of welding and curved surface processing, but when the target deformation amount is F and the allowable deformation or deviation from the processing amount is d. .Alpha. Can also be expressed by these ratios (d / F). When α is set in this way, it can be evaluated that all deformation variations are caused by the difference between σL and σC, so that the deformation variations are evaluated with higher accuracy and the necessary accuracy can be reliably obtained. That is, there are variations in the heating conditions in addition to σL and σC, but the difference between σL and σC is strictly determined assuming that the deformation variation due to these other factors is caused by the difference between σL and σC. As a result, even if there are variations in the heating conditions and the like, it is possible to suppress the deformation amount within an allowable variation range.
[0024]
For example, in a steel sheet having a thickness of 40 mm or less used for a hull, assuming that the target deformation amount (or processing amount) is 100 mm, the allowable deviation amount from this processing amount is 3 mm. Is generally applicable to steel plates having a thickness of 40 mm or less, and if α = 0.03 is set in advance at this time, sufficient accuracy can be reliably obtained in most welding / curved surface processing.
[0025]
On the other hand, as the plate thickness increases, the heat input during welding and curved surface processing increases, so the influence of the difference between the yield stress σL in the rolling direction and the yield stress σC in the direction orthogonal to the plate direction is eliminated. The value of α required for steel plates with a thickness exceeding 40 mm can be set larger than that for thin plates. For example, if α = 0.05, sufficient accuracy can be reliably obtained in most welding and curved surface processing. become.
[0026]
Next, the manufacturing method of this invention is demonstrated. First, it is considered that the difference in yield stress obtained by a tensile test using test pieces taken in the L direction and the C direction is caused by a subtle difference in temperature and reduction during hot rolling. However, at present, there is no technique for simultaneously controlling the yield stress in the L direction or the C direction after rolling by the temperature and reduction amount in hot rolling, and the conventional rolling method is a steel sheet that satisfies the formula (1). Could not get.
[0027]
As a result of studying the method for realizing the steel plate as described above, the present inventors have been able to produce a steel plate that satisfies the above formula (1) by utilizing the cold correction with the roller leveler. The manufacturing principle in the method of the present invention is as follows.
[0028]
When the steel sheet is straightened cold, plastic strain is mainly introduced in the straightening direction. Due to the plastic strain introduced in the correction direction, the steel sheet is work-hardened, and the degree of rise varies depending on the correction direction in the plate surface. The present inventors investigated the influence of such effects on curved surface processing by linear heating as a processing example. The result is shown in FIG.
[0029]
That is, FIG. 4 is a graph showing the effect of correction on the difference in deformation amount depending on the bending direction, but there is a difference in the deformation amount between the L direction and the C direction in the steel plate before correction (without correction). However, it can be seen that the difference is almost eliminated in the steel sheet after correction (with correction).
[0030]
The method of the present invention utilizes these properties. Specifically, the yield stress σL in the rolling direction and the yield stress σC in the width direction are compared, and the direction with the smaller value is taken as the correction direction, and along this direction. By correcting the difference between σL and σC using a roller leveler, variations in deformation during welding or curved surface processing are eliminated.
[0031]
Further, when correcting the above method, it is only necessary to introduce a plastic strain sufficient to eliminate the difference according to the difference between σL and σC. Specifically, if correction is performed so as to satisfy the relationship of the following equation (2), the difference between σL and σC can be controlled reliably, and as a result, variation in deformation can be prevented. The relationship between the correction conditions and the introduced surface strain can be easily calculated by methods described in various documents (for example, “correction processing”, edited by the Japan Society for Technology of Plasticity).
ε = | σL−σC | × b (2)
However, (epsilon) shows the absolute value of the plastic distortion introduce | transduced on the steel plate surface during correction | amendment, b shows the value decided by steel grade, respectively.
[0032]
For example, the coefficient b can be obtained based on the work hardening coefficient H of the steel sheet measured by a tensile test or the like according to the steel type [the following formula (3)].
b = m × 1 / H (3)
Here, the coefficient m may be determined in advance from the measurement results of σL and σC and work hardening coefficient before and after correction on various steel plates.
[0033]
For example, in the case of low carbon steel, if the unit of yield stress is kgf / mm 2 according to the steel type, the value is about b = 0.01 to 0.025.
[0034]
In addition, it does not specifically limit about the kind of steel plate made into object by this invention, For example, various steel plates, such as carbon steel, low alloy steel, steel for boilers, steel for pressure vessels, are mentioned.
[0035]
Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are not of a nature that limits the present invention, and any design changes characterized by the gist of the preceding and following descriptions are technical techniques of the present invention. It is included in the scope.
[0036]
【Example】
Example 1
Prepare a steel sheet that satisfies the requirement [formula (1)] defined in the present invention (the material of the present invention) and a steel sheet that does not satisfy the material (comparative material), and perform curved surface processing by linear heating on these steel sheets under the same conditions. The degree of deformation variation from the target machining amount was investigated. At this time, “target material and processing procedure” are as follows, and the value of the left side [2 × | σL−σC | / (σL + σC)] of the equation (1) in each steel plate is as shown in Table 1 below. It is. The state of the linear heating position at this time is shown in FIG. 5 [FIG. 5 (a) is a plan view, and FIG. 5 (b) is a cross-sectional view taken along line AB].
[0037]
[0038]
[Table 1]
[0039]
The result (deviation amount from the target value of the bending amount) is shown in Table 2 below. In the comparative material, the variation in deformation from the target processing amount exceeding the allowable amount occurs, whereas in the present invention material all Is within the allowable range.
[0040]
[Table 2]
[0041]
Example 2
For steel sheets having the same yield stress in the C direction, cold-corrected steel sheets according to the present invention (materials of the present invention) and non-coated steel sheets (comparative materials) are prepared. Direction), and joint shrinkage variation from the set plate shrinkage was investigated. The “target material and welding procedure” at this time are as follows, and the value of the left side [2 × | σL−σC | / (σL + σC)] of the equation (1) in each steel plate before correction is shown in Table 3 below. As shown in The state of the welding position at this time is shown in FIG.
[0042]
<Target material and welding procedure>
Type of steel plate: 500 N / mm Grade 2 steel plate Size: Plate thickness 16 mm, plate width 2500 mm, plate length 2500 mm
Welding position: Fig. 6
Welding conditions: Submerged welding (current 460 A, voltage 32 V, welding speed 0.43 m / min, 3 pass required processing accuracy: set shrinkage amount = 5 mm, allowable shrinkage variation = 0.5 mm
[0043]
[Table 3]
[0044]
No. in Table 3 Among the
[0045]
[Table 4]
[0046]
The results are shown in Table 5 below (the amount of deviation from the set value of the shrinkage amount). In contrast, in the comparative material, shrinkage variation from the set shrinkage amount exceeding the allowable amount occurs, whereas in the present invention material all It can be seen that it is within the allowable range.
[0047]
[Table 5]
[0048]
【The invention's effect】
The present invention is configured as described above, and it has been possible to realize a steel sheet in which deformation or processing variation during welding or curved surface processing is reduced as much as possible, and subsequent maintenance is unnecessary.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory view showing a state in which the amount of deformation is measured when curved surface processing is performed by linear heating.
FIG. 2 is a graph showing the relationship between the bending direction and deformation amount of a steel plate.
FIG. 3 is a graph showing the relationship between the L direction yield stress and the amount of deformation when the bending direction is the L direction for a steel sheet having a C direction yield stress of 410 N / mm 2 .
FIG. 4 is a graph showing the effect of correction on the difference in deformation amount depending on the bending direction.
5 is an explanatory diagram showing a state of a linear heating position in Example 1. FIG.
6 is an explanatory view showing a state of a welding position in Example 2. FIG.
Claims (3)
2×|σL−σC|/(σL+σC)≦α ……(1)
但し、αは必要な加工精度によって予め決まる値であり、鋼板の厚みが40mm以下のときには0.03であり、鋼板の厚みが40mmを超えるときには0.05である。A steel sheet having a small deformation or variation in processing at the time of welding or curved surface processing, wherein the yield stress σL in the rolling direction and the yield stress σC in the width direction satisfy the relationship of the following formula (1).
2 × | σL−σC | / (σL + σC) ≦ α (1)
However, α is a value determined in advance by the required processing accuracy, and is 0.03 when the thickness of the steel plate is 40 mm or less, and 0.05 when the thickness of the steel plate exceeds 40 mm.
ε=|σL−σC|×b ……(2)
但し、εは矯正中に鋼板表面に導入される塑性歪みの絶対値、bは鋼種によって決まる値を夫々示す。The manufacturing method according to claim 2, wherein correction is performed so as to satisfy the relationship of the following expression (2).
ε = | σL−σC | × b (2)
However, (epsilon) shows the absolute value of the plastic distortion introduce | transduced on the steel plate surface during correction | amendment, b shows the value decided by steel grade, respectively.
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