JP3774619B2 - Manufacturing method of thick steel plate with excellent secondary workability - Google Patents

Description

【００１０】
上下降伏点は伸び率０．２％以上の圧下を加えることによって解消することを確認した。次に、軽圧下後の圧延方向および板幅方向の耐力の平均値を原板の圧延方向および板幅方向の耐力の平均値で除した値を耐力比と定義し、耐力比に及ぼす軽圧下の影響を調べた。その結果を図２に示す。図２より明らかなように軽圧下を加えることによって、耐力が原板よりも低減することが明らかになった。その効果は厚鋼板の種類によって異なるが伸び率が０．２％未満では耐力として原板とあまり変わらないことが判明した。このことから伸び率の下限は０．２％とした。また、図２より明らかなように。伸び率が大きくなると耐力は原板以上になる。耐力が原板よりも小さくなる範囲は厚鋼板の種類によって異なるが伸び率が約１．２％までは耐力が小さいことが明らかになった。なお、耐力の観点からは伸び率の好ましい値は図２より約０．５％程度であることが分かる。以上のことから伸び率の上限は１．２％とした。また、種々の検討を行った結果、実機では、製造コスト面を考慮すると、少なくとも仕上圧延機で圧延された圧延板の冷却装置を有し、該冷却装置の下流側に、少なくとも１台の軽圧下圧延機を配備した厚鋼板圧延製造設備において、上述の伸び率を与えるのが最も有利であることを突き止め、これを本発明の限定範囲とした。
【００１１】
図３に圧延機の形状制御端であるワークロールベンダーを操作して端伸びから中伸び方向に変化させた際の形状変化挙動を示す。図３に示すように板厚が５ｍｍ未満の材料を圧延した場合、フラットな板形状が得られるベンダーの値は１点であり、その際圧延された材料を切断しても反りや曲がりが発生しないことを確認した。これに対し、板厚が５ｍｍ以上の材料を圧延した場合、フラットな板形状が得られるベンダーの値は複数存在し、その際圧延された材料を切断すると、反りや曲がりが発生したりしなかったりすることを確認した。以上のことから板厚５ｍｍ以上の厚鋼板では形状不感帯が存在し、見掛け上フラットな材料でも切断すると反りや曲がりが発生する、潜在的な平坦度不良製品があり得ることが判明した。また、幅方向に複数の歪みゲージを材料の表裏目に張り付け切断し、切断しても反りや曲がりが発生しない残留応力分布差を明らかにした結果、切断しても反りや曲がりが発生しない板幅方向の残留応力分布差は±２０ＭＰａ以下で有ることが明らかになった。この知見をもとに本発明がなされた。
【００１２】
上述の板幅方向の残留応力差が±２０ＭＰａ以下である板厚５ｍｍ以上の厚鋼板は、圧延機の後の圧延材の板形状を目視やセンサーをもってしても、形状不感帯のために製造することは困難である。これを実現するためには圧延機自体が圧延時の板幅方向の残留応力分布を推定することの可能な圧延機が不可欠である。以上の理由から、該軽圧下圧延機として、上下少なくともどちらか一方のロールアセンブリーが、軸方向に３分割以上に分割された分割バックアップロールによってワークロールを支持する機構であり、各分割バックアップロールには独立した荷重検出装置と圧下装置とが配置された板圧延機を用いることが最良であることを見出した。この知見をもとに本発明がなされた。
【００１３】
【実施例】
実施は図４に示す厚鋼板製造設備で行った。図４において、冷却装置２は、仕上圧延機１の下流側に位置し、圧延方向を３で示している。冷却装置２の下流側に、軽圧下圧延機４が配備されている。軽圧下圧延機４の前後にピンチロール５および６が配備されており、軽圧下圧延機４の後ろには幅方向板厚測定装置７が設置されている。
【００１４】
本発明の実施例では仕上圧延機１は、一対のワークロールを一対のバックアップロールで支持する機構の４段圧延機を用いた。冷却装置２では、仕上圧延機１の下流側に位置し、圧延が終了した後の厚鋼板を所定の温度まで冷却する。冷却装置２は、水を冷媒として使用する設備を用いた。仕上圧延機１と冷却装置２との間には、図示はしていないがローラレベラー等の装置が配備されている。冷却装置２の下流側には、軽圧下圧延機４が配備されている。この軽圧下圧延機４の詳細を図５に示す。
【００１５】
この軽圧下圧延機４は、電動モータによるパスライン調整機８（ロール交換した際のロール径の変化に対応してパスラインを調整する装置）および油圧圧下を用いた主圧下装置９（圧下位置は油圧シリンダーの位置を検出することによって測定）で上下する上下のインナーハウジング内に、図５（ｂ）に示すように、軸方向に１５分割した直径７５０ｍｍ、胴長３００ｍｍの分割バックアップロール１０、１１によって直径３００ｍｍ、胴長４５００ｍｍの上下のワークロール１２を支持する機構を有しており、各々の分割バックアップロール１０ａ〜１０ｇ、１１ａ〜１１ｈには、それぞれ独立に荷重検出装置と圧下機構および位置検出機構を備えている。図示はしていないが上下のワークロールは駆動モータによって圧延に必要なトルクを伝達されている。さらに、インナーハウジング内にワークロールチョックが設けられている。板厚測定装置７としてγ線による非接触板厚計が軽圧下知能圧延機から８ｍ下流に設置されている。
【００１６】
厚鋼板の板幅方向の残留応力分布差を±２０ＭＰａ以下にする具体的な方法に関しては、例えば発明者らが既に出願している特開平６−２６２２２８号公報に公示されている方法を用いた。
すなわち、第ｉ分割バックアップロールに作用する荷重をｑ_ｉ、その位置に対応する圧延材〜ワークロール間荷重をｐ_ｉとし、ワークロール軸心たわみの変形マトリクスをＫ^Ｗ _ｉｊ、バックアップロール系の変形マトリクスをＫ^Ｂ _ｉｊ、ロールクラウンの型式で表現したワークロールプロフィルをＣ^Ｗ _ｉ、分割バックアップロールプロフィルをＣ^Ｂ _ｉ、上ワークロール軸心たわみをｙ^Ｗ _ｉとすると、分割バックアップロールとワークロールの適合条件より、式（１）が得られる。
ｙ^Ｗ _ｉ＝Ｋ^Ｂ _ｉｊｑ_ｊ＋Ｃ^Ｗ _ｉ＋Ｃ^Ｂ _ｉ （１）
【００１７】
なお、本明細書の数式では、同添字の繰り返しがある場合にはアインシュタインの総和規約を用いて表現する。また、Ｋ^Ｂ _ｉｊは第ｊ分割バックアップロールに単位荷重が負荷された時の第ｉ分割バックアップロールの変位を表す影響係数マトリクスであるが、ここでは、ハウジングの変形およびワークロール〜分割バックアップロールの接触による両ロールの偏平変形を含めた変形マトリクスを表す。Ｋ^Ｂ _ｉｊ、Ｋ^Ｗ _ｉｊ、ｙ^Ｗ _ｉはすべてミルセンターからの相対位置のみを抽出する。
【００１８】
一方、上ワークロールたわみは、変形マトリクスＫ^Ｗ _ｉｊおよび圧延材〜ワークロール間に作用する圧延荷重分布ｐ_ｉを用いて、式（２）で表される。
ｙ^Ｗ _ｉ＝Ｋ^Ｗ _ｉｊ（ｐ_ｊ−ｑ_ｊ） （２）
式（１）、式（２）よりｙ^Ｗ _ｉを消去し、整理すると式（３）が得られる。
ｑ_ｉ＝［Ｋ^Ｂ＋Ｋ^Ｗ］^−１ _ｉｊ（Ｋ^Ｗ _ｊｋｐ_ｋ−Ｃ^Ｗ _ｊ−Ｃ^Ｂｊ） （３）
上式の右辺で、［Ｋ^Ｂ＋Ｋ^Ｗ］^−１ _ｉｊはＫ^Ｗ _ｉｊ＋Ｋ ^Ｂ _ｉｊ の逆マトリクスである。
【００１９】
ところで、圧延荷重ｐ_ｉは、一般に、入側板厚Ｈ、出側板厚ｈ、変形抵抗ｋ、摩擦係数μ、平均入側張力σ_ｂ、平均出側張力σ_ｆ、板形状を表現する伸びひずみ差Δεの関数であり、式（４）で与えられる。
ｐ_ｉ＝ｐ_ｉ（Ｈ、ｈ、ｋ、μ、σ_ｂ、σ_ｆ、Δε） （４）
ここで、ロールバイト中のｋ、μは板幅方向にほとんど一定であり計算および実験によって求めることができ、入側板厚Ｈと出側板厚ｈと平均入側張力σ_ｂと平均出側張力σ_ｆは所望とする圧延条件を入力することによって与えられる。
残留応力Δσ_ｉと伸びひずみ差Δεの関係は材料のヤング率Ｅを用いると式（５）で与えられる。
Δσ_ｉ＝Δε・Ｅ （５）
【００２０】
従って、式（５）より、目標とする伸びひずみ差Δεを求め、この値を式（４）に代入すれば、所望の残留応力差が得られるための圧延荷重ｐ_ｉが求められる。
この圧延荷重ｐ_ｉを式（３）に代入することによって、所望の形状が得られるための各分割バックアップロールの荷重ｑ_ｉが求められる。従って、各分割バックアップロールの荷重がｑ_ｉと一致するように各分割バックアップロールの荷重を見ながら各分割バックアップロールの変位を調整した。
【００２１】
圧延材として、材質は表１のＡと同じもので、板厚４０ｍｍ、板幅４０００ｍｍ、長さ６０ｍの厚鋼板（耐力約４５０ＭＰａ）を用いた。板形状は見掛け上フラットであった。この材料を伸び率０．５％で、残留応力分布差として±５ＭＰａ目標で圧延した。残留応力分布の評価方法として圧延前後の材料を２ｍに切断し切断前後の曲がりやうねりを調べた。また、耐力に関しては圧延前後の板から引っ張り試験片を作成し、引っ張り試験を行い比較した。圧延前後の材料で均一変形に関しては３点曲げを行い、リューダース帯の発生や表面の性状を調べた。また、加工性に関しては３点曲げを行う際の荷重で評価した。結果を表２に示す。表中で従来技術は圧延前の材料の特性を表す。表２から明らかなように本発明によって、曲げ加工やプレス加工や剪断加工などの二次加工性に優れた厚鋼板が得られた。
【００２２】
【表２】

【００２３】
【発明の効果】
本発明の製造方法によって得られる厚鋼板を用いることにより、曲げ加工やプレス加工時の加工力や摩耗およびその製造設備コストを低減でき、剪断加工などを行っても曲がりやうねりの発生しないため、矯正や仕上げ加工を省略し、製造コストを低減できる。また、本発明の製造方法によれば、上記した二次加工性の優れた厚鋼板を確実に得ることができることから、その工業上の寄与するところ大である。
【図面の簡単な説明】
【図１】 市販の厚鋼材を引っ張り試験した際の応力−伸び線図の一例である。
【図２】 耐力比に及ぼす軽圧下の影響を示す図である。
【図３】 ワークロールベンダーを操作して端伸びから中伸び方向に変化させた際の形状変化挙動を示す一例である。
【図４】 本発明の実施例に用いた厚鋼板製造設備の概略を示す図である。
【図５】 （ａ）は本発明の実施例に用いた軽圧下圧延機の概略を示す図、（ｂ）は軽圧下圧延機における分割バックアップロールの具体例を示す平面略図である。
【符号の説明】
１ 仕上圧延機
２ 冷却装置
３ 圧延板進行方向
４ 軽圧下圧延機
５ 軽圧下圧延機前面ピンチロール
６ 軽圧下圧延機後面ピンチロール
７ 幅方向板厚測定装置
８ パスライン調整機
９ 主圧下装置
１０、１１ バックアップロール
１０ａ〜１０ｇ、１１ａ〜１１ｈ 分割バックアップロール
１２ ワークロール[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a thick steel plate excellent in secondary workability such as bending, pressing or shearing with a plate thickness of 5 mm or more and a plate width of 2.5 m or more.
[0002]
[Prior art]
In recent years, quality requirements for steel materials called thick steel plates with a thickness of 5 mm or more and a width of 2.5 m or more are becoming stricter, and various rolling and straightening techniques have been developed to meet this requirement. In general, the above-described thick steel plate is a steel plate rolling facility, that is, a rolled plate that has undergone finish rolling in a thick plate rolling mill, is subjected to a cooling device and / or a cooling bed, and is subjected to adjustments such as shearing, heat treatment, shape correction, and painting. It is transported to the process, where it is shipped as a product. A processing maker uses this product to cut it to a desired size, and then performs secondary processing such as bending or pressing, and then welding to manufacture a final product.
When performing secondary processing at the manufacturer, even with the same material, the processing force is small, such as pressing and bending, and deformation is not concentrated locally. Products that have no undulations or bends are desired.
[0003]
In response to these requirements, secondary workability has been dealt with by changing the alloy components of the thick steel plate, but there has been a problem of increasing costs due to the addition of alloy components and changes in manufacturing conditions. In addition, when the product is swelled or bent when it is cut into a predetermined dimension, there is no means to cope with it, and it has been dealt with by correcting with a leveler or a press in order to guarantee flatness at the time of product shipment.
[0004]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a method for producing a thick steel plate that is excellent in secondary workability and has no undulation or bending when cut.
[0005]
[Means for Solving the Problems]
In order to solve the above problems,
Claim 1 of the present invention has a cooling device for a rolled sheet rolled at least by a finish rolling mill, and a steel plate rolling facility provided with at least one light rolling mill on the downstream side of the cooling device, When manufacturing a thick steel plate with a plate thickness of 5 mm or more and a plate width of 2.5 m or more,
As a rolling mill that performs light reduction rolling, at least one of the upper and lower roll assemblies has a mechanism for supporting a work roll by a divided backup roll divided into three or more in the axial direction. Using a plate rolling machine in which an independent load detection device and a reduction device are arranged,
While controlling the displacement of the backup roll based on q _i obtained by the following equations (3), (4) and (5) ,
A method for producing a thick steel sheet, wherein the rolled material is produced by cold light rolling at an elongation of 0.2% or more and 1.2% or less with the light rolling mill, wherein:
^{_{q i = [K B + K}} W] -1 ij (K W jk p k -C W j -C B j) (3)
p _i = p _i (H, h, k, μ, σ _b , σ _f , Δε) (4)
Δσ _i = Δε · E (5)
q _i : Load acting on the i-th divided backup roll
p _i : Load between rolled material and work roll corresponding to the position
K ^W _ij : Deformation matrix of work roll axis deflection
K ^B _ij : Deformation matrix of backup roll system
C W ^_i: work roll profile that was expressed in the type of roll crown
C ^B _i : Split backup roll profile
[K ^B + K ^W ] ⁻¹ _ij : Inverse matrix of K ^W _ij + K ^B _ij
H: Thickness on the entry side
h: Outboard thickness
k: Deformation resistance
μ: Friction coefficient
σ _b : average entry side tension
σ _f : Average delivery tension
Δε: Elongation strain difference
Δσ _i : Residual stress−20 ≦ Δσ _i ≦ 20 [MPa]
E: Young's modulus of the material,
According to claim 2 of the present invention, the thick steel plate is mass,
C: 0.08 to 0.46%,
Si: 0.15-0.35%,
Mn: 0.66 to 1.67%
P: 0.017% or less,
S: 0.007% or less,
And the inevitable impurity element, comprising the balance Fe , The method for producing a thick steel plate according to claim 1 ,
According to a third aspect of the present invention, the thick steel plate is mass,
Cu: 0.14% or less,
Ni: 0.08% or less,
Cr: 0.25% or less,
V: 0.23% or less,
The method for producing a thick steel plate according to claim 2, wherein any one or more of Ti: 0.08% or less of an alloy element is included.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be specifically described below. First, a specific description will be given of how the thick steel plate manufacturing method of the present invention was completed.
FIG. 1 is an example of a stress-elongation diagram when a commercial thick steel material is subjected to a tensile test. As shown in FIG. 1, a commercially available thick steel plate has an upper and lower yield point between about 0.05 to 0.2% in elongation. When processing such a material, it is necessary to apply a stress higher than the upper yield point, and therefore it is necessary to apply a corresponding press pressure or bending load. Therefore, a processing apparatus that performs such secondary processing requires a larger capacity, and the equipment cost increases. Further, when the load is high, there is a problem that the tool life of the processing apparatus is shortened due to wear or the like. Furthermore, if there is an upper and lower yield point, there is a problem that a Luders band is generated during deformation following the secondary processing, the surface properties are disturbed and fine irregularities are generated, and deformation is concentrated locally. . When such deformation occurs, there is a problem that the corrosion resistance of the portion deteriorates. In order to avoid this, it is necessary to increase the strain rate during processing. In other words, high-speed machining is required, and high-response control associated therewith is required. Therefore, this also increases the equipment cost and the manufacturing cost. The inventors have found that in order to solve the above problems by performing a bending test and a corrosion test on various thick steel plates, a countermeasure can be obtained by eliminating the upper and lower yield points of the material.
[0007]
Moreover, when processing a thick steel plate, a thick steel plate may be previously cut | disconnected to a desired dimension. Such a cutting process is performed on a thick steel plate having a width of 2.5 m or more. When this thick steel plate is cut even if it is completely flat, warping or bending called camber occurs. And found that productivity is significantly reduced. Based on these findings, the onset Akira has been made.
[0008]
Next, other features of the present invention will be specifically described below. The effect of temper rolling of a thin sheet material is known as a method for eliminating the upper and lower yield points. In order to confirm whether this effect is effective even with a thick steel plate, a 20 mm thick steel plate having the chemical components shown in Table 1 is lightly rolled to an elongation of 2.0%, and a sample after rolling is cut out. A tensile test was performed.
[0009]
[Table 1]

[0010]
It was confirmed that the upper and lower yield points were eliminated by applying a reduction with an elongation of 0.2% or more. Next, the value obtained by dividing the average value of the proof stress in the rolling direction and the sheet width direction after the light reduction by the average value of the proof stress in the rolling direction and the plate width direction of the original sheet is defined as the proof stress ratio. The effect was investigated. The result is shown in FIG. As is clear from FIG. 2, it was revealed that the proof stress is reduced as compared with the original plate by applying light reduction. The effect differs depending on the type of thick steel plate, but it has been found that when the elongation is less than 0.2%, the yield strength is not much different from the original plate. For this reason, the lower limit of elongation was set to 0.2%. As is clear from FIG. When the elongation increases, the proof stress becomes more than the original plate. The range in which the proof stress is smaller than that of the original plate differs depending on the type of the thick steel plate, but it has been clarified that the proof strength is small up to about 1.2% elongation. From the viewpoint of yield strength, it can be seen from FIG. 2 that a preferable value of elongation is about 0.5%. From the above, the upper limit of the elongation rate was set to 1.2%. In addition, as a result of various studies, the actual machine has a cooling device for at least the rolled sheet rolled by the finish rolling mill in consideration of the manufacturing cost, and at least one light machine is provided on the downstream side of the cooling device. In the thick steel plate rolling production facility provided with the rolling mill, it was determined that it is most advantageous to give the above-mentioned elongation rate, and this was defined as a limited range of the present invention.
[0011]
FIG. 3 shows the shape change behavior when the work roll bender, which is the shape control end of the rolling mill, is operated to change from the end extension to the middle extension direction. As shown in FIG. 3, when a material with a plate thickness of less than 5 mm is rolled, the value of the bender for obtaining a flat plate shape is one point, and even when the rolled material is cut, warping or bending occurs. Confirmed not to. On the other hand, when a material having a thickness of 5 mm or more is rolled, there are a plurality of values of the bender that can obtain a flat plate shape. When the rolled material is cut at that time, no warping or bending occurs. I confirmed that. From the above, it has been found that there is a potential inferior flatness product in which a shape dead zone exists in a thick steel plate having a thickness of 5 mm or more, and warping or bending occurs when cutting even an apparently flat material. In addition, a plurality of strain gauges in the width direction are attached to the front and back of the material and cut, and the residual stress distribution difference that does not cause warping or bending even if cut is clarified. It became clear that the residual stress distribution difference in the width direction was ± 20 MPa or less. The present invention was made based on this finding.
[0012]
The above-mentioned thick steel plate with a thickness of 5 mm or more whose residual stress difference in the plate width direction is ± 20 MPa or less is produced for the shape dead zone even if the plate shape of the rolled material after the rolling mill is visually or with a sensor. It is difficult. In order to realize this, a rolling mill capable of estimating the residual stress distribution in the sheet width direction during rolling is indispensable. For the above reasons, as the light rolling mill, at least one of the upper and lower roll assemblies is a mechanism for supporting a work roll by a divided backup roll divided into three or more in the axial direction, and each divided backup roll It has been found that it is best to use a plate rolling machine in which an independent load detection device and a reduction device are arranged. The present invention was made based on this finding.
[0013]
【Example】
The implementation was performed at the thick steel plate manufacturing facility shown in FIG. In FIG. 4, the cooling device 2 is located on the downstream side of the finish rolling mill 1, and the rolling direction is indicated by 3. A light reduction rolling mill 4 is disposed downstream of the cooling device 2. Pinch rolls 5 and 6 are arranged before and after the light rolling mill 4, and a width direction plate thickness measuring device 7 is installed behind the light rolling mill 4.
[0014]
In the embodiment of the present invention, the finishing mill 1 is a four-high rolling mill having a mechanism for supporting a pair of work rolls with a pair of backup rolls. The cooling device 2 is located downstream of the finishing mill 1 and cools the thick steel plate after the rolling is finished to a predetermined temperature. The cooling device 2 used equipment using water as a refrigerant. Although not shown, a device such as a roller leveler is disposed between the finishing mill 1 and the cooling device 2. On the downstream side of the cooling device 2, a light rolling mill 4 is provided. Details of the light rolling mill 4 are shown in FIG.
[0015]
This light rolling mill 4 includes a pass line adjuster 8 (an apparatus that adjusts a pass line in response to a change in roll diameter when a roll is replaced) by an electric motor, and a main reduction apparatus 9 (a reduction position) using hydraulic reduction. Is measured by detecting the position of the hydraulic cylinder), as shown in FIG. 5 (b), in the upper and lower inner housings, as shown in FIG. 5 (b), the divided backup roll 10 having a diameter of 750 mm and a barrel length of 300 mm, 11 has a mechanism for supporting upper and lower work rolls 12 having a diameter of 300 mm and a barrel length of 4500 mm. Each of the divided backup rolls 10a to 10g and 11a to 11h has a load detection device, a reduction mechanism, and a position independently. A detection mechanism is provided. Although not shown, the upper and lower work rolls are transmitted with torque necessary for rolling by a drive motor. Furthermore, a work roll chock is provided in the inner housing. A non-contact plate thickness gauge using γ rays is installed as a plate thickness measuring device 7 8 m downstream from the light rolling intelligent rolling mill.
[0016]
Regarding a specific method of setting the residual stress distribution difference in the plate width direction of the thick steel plate to ± 20 MPa or less, for example, a method published in Japanese Patent Laid-Open No. Hei 6-262228 already filed by the inventors was used. .
That is, the load of q _i which acts on the i split backup _rolls, a load-rolled material - work roll corresponding to the position and p _i, deform the deformation matrix work roll axis deflection of K ^W _ij, backup roll system Assuming that the matrix is K ^B _ij , the work roll profile expressed in the form of roll crown is C ^W _i , the divided backup roll profile is C ^B _i , and the upper work roll axis deflection is y ^W _i , the divided backup roll and work roll Equation (1) is obtained from the matching conditions.
y ^W _i = K ^B _ij q _j + C ^W _i + C ^B _i (1)
[0017]
In addition, in the mathematical expression of this specification, when there is repetition of the subscript, it is expressed using Einstein's sum rules. K ^B _ij is an influence coefficient matrix representing the displacement of the i-th divided backup roll when a unit load is applied to the j-th divided backup roll. Here, the deformation of the housing and the work roll to the divided backup roll It represents a deformation matrix including flat deformation of both rolls due to contact. K ^B _ij , K ^W _ij , and y ^W _i all extract only the relative position from the mill center.
[0018]
On the other hand, the deflection upper work rolls, using the rolling force distribution p _i acting between deformation matrix K ^W _ij and the rolled material - work roll is represented by the formula (2).
^{_{y W i = K W ij (}} p j -q j) (2)
Equation (1), erase the more ^y _{W i} Equation (2), Equation (3) is obtained and arranging.
^{_{q i = [K B + K}} W] -1 ij (K W jk p k -C W j -C B j) (3)
In the right side of the above equation, [K ^B + K ^W ] ⁻¹ _ij is an inverse matrix of K ^W _ij + K ^B _ij .
[0019]
Incidentally, the rolling load p _i is generally thickness at entrance side H, delivery side thickness h, deformation resistance k, friction coefficient mu, the average entry side tension sigma _b, the average exit side tension sigma _f, elongation strain difference representing the shape of a flat plate It is a function of Δε and is given by equation (4).
p _i = p _i (H, h, k, μ, σ _b , σ _f , Δε) (4)
Here, k 1 and μ in the roll bite are almost constant in the plate width direction and can be obtained by calculation and experiment. The entrance side plate thickness H, the exit side plate thickness h, the average entrance side tension σ _b, and the average exit side tension σ _f is given by inputting desired rolling conditions.
The relationship between the residual stress Δσ _i and the elongation strain difference Δε is given by equation (5) using the Young's modulus E of the material.
Δσ _i = Δε · E (5)
[0020]
Therefore, the equation (5), determine the elongation strain difference Δε a target, by substituting this value into equation (4), rolling load p _i for desired residual stress difference can be obtained is determined.
By substituting this rolling load p _i in formula (3), the load q _i of each divided backup roll for the desired shape is obtained is obtained. Therefore, the displacement of each divided backup roll was adjusted while observing the load of each divided backup roll so that the load of each divided backup roll coincided with q _i .
[0021]
As the rolled material, the same material as A in Table 1 was used, and a thick steel plate (with a yield strength of about 450 MPa) having a plate thickness of 40 mm, a plate width of 4000 mm, and a length of 60 m was used. The plate shape was apparently flat. This material was rolled with an elongation of 0.5% and a residual stress distribution difference of ± 5 MPa. As a method for evaluating the residual stress distribution, the material before and after rolling was cut into 2 m, and the bending and waviness before and after cutting were examined. Moreover, regarding the proof stress, a tensile test piece was created from the plate before and after rolling, and a tensile test was performed for comparison. The material before and after rolling was subjected to three-point bending for uniform deformation, and the occurrence of Lueders band and the surface properties were examined. Further, the workability was evaluated by the load when performing the three-point bending. The results are shown in Table 2. In the table, the prior art represents the characteristics of the material before rolling. As is apparent from Table 2, the present invention yielded a thick steel plate excellent in secondary workability such as bending, pressing and shearing.
[0022]
[Table 2]

[0023]
【The invention's effect】
By using the thick steel plate obtained by the production method of the present invention, it is possible to reduce the working force and wear at the time of bending and pressing and its production equipment cost, and even if shearing or the like is performed, bending and undulation do not occur. Correction and finishing can be omitted, and manufacturing costs can be reduced. Moreover, according to the manufacturing method of this invention, since the above-mentioned thick steel plate excellent in secondary workability can be obtained reliably, the industrial contribution is large.
[Brief description of the drawings]
FIG. 1 is an example of a stress-elongation diagram when a commercial thick steel material is subjected to a tensile test.
FIG. 2 is a diagram showing the influence of light pressure on the yield strength ratio.
FIG. 3 is an example showing a shape change behavior when the work roll bender is operated to change from an end extension to a middle extension direction.
FIG. 4 is a diagram showing an outline of a thick steel plate manufacturing facility used in an example of the present invention.
5A is a diagram showing an outline of a light rolling mill used in an embodiment of the present invention, and FIG. 5B is a schematic plan view showing a specific example of a split backup roll in the light rolling mill.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Finishing mill 2 Cooling device 3 Rolling plate advancing direction 4 Light rolling mill 5 Light rolling mill front pinch roll 6 Light rolling mill rear pinch roll 7 Width direction plate thickness measuring device 8 Pass line adjuster 9 Main rolling rolling device 10 11 Backup rolls 10a to 10g, 11a to 11h Divided backup rolls 12 Work rolls

Claims (3)

At least 5 mm in thickness and 2 mm in plate width by a steel plate rolling facility having a cooling device for at least a rolled plate rolled by a finish rolling mill and having at least one light rolling mill provided on the downstream side of the cooling device. When manufacturing thick steel plates of 5m or more,
As a rolling mill that performs light reduction rolling, at least one of the upper and lower roll assemblies has a mechanism for supporting a work roll by a divided backup roll divided into three or more in the axial direction. Using a plate rolling machine in which an independent load detection device and a reduction device are arranged,
While controlling the displacement of the backup roll based on q _i obtained by the following equations (3), (4) and (5) ,
A method for producing a thick steel sheet, comprising producing a rolled material by cold light rolling at an elongation of 0.2% or more and 1.2% or less with the light rolling mill.
^{_{q i = [K B + K}} W] -1 ij (K W jk p k -C W j -C B j) (3)
p _i = p _i (H, h, k, μ, σ _b , σ _f , Δε) (4)
Δσ _i = Δε · E (5)
q _i : Load acting on the i-th divided backup roll
p _i : Load between rolled material and work roll corresponding to the position
K ^W _ij : Deformation matrix of work roll axis deflection
K ^B _ij : Deformation matrix of backup roll system
C W ^_i: work roll profile that was expressed in the type of roll crown
C ^B _i : Split backup roll profile
[K ^B + K ^W ] ⁻¹ _ij : Inverse matrix of K ^W _ij + K ^B _ij
H: Thickness on the entry side
h: Outboard thickness
k: Deformation resistance
μ: Friction coefficient
σ _b : average entry side tension
σ _f : Average delivery tension
Δε: Elongation strain difference
Δσ _i : Residual stress−20 ≦ Δσ _i ≦ 20 [MPa]
E: Young's modulus of material The steel plate is mass,
C: 0.08 to 0.46%,
Si: 0.15-0.35%,
Mn: 0.66 to 1.67%
P: 0.017% or less,
S: 0.007% or less,
The method for producing a thick steel plate according to claim 1, further comprising an inevitable impurity element and the balance being Fe . The steel plate is mass,
Cu: 0.14% or less,
Ni: 0.08% or less,
Cr: 0.25% or less,
V: 0.23% or less,
The method for producing a thick steel plate according to claim 2, comprising any one or more of Ti: 0.08% or less of alloy elements.

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