JP3606825B2 - Precision rolling method for steel bars and wire rods - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、棒鋼及び線材の精密圧延方法に関し、詳しくは、１台以上の２ロール圧延機及び、仕上げ圧延機群を構成する３台の３ロール圧延機を用いて、高い寸法精度で噛み出しを生ずることなく、断面形状が円形の棒鋼及び線材を得る圧延方法に関する。
【０００２】
【従来の技術】
熱間圧延された棒鋼及び線材は、通常、軟化焼鈍や球状化焼鈍を受け、更にその後冷間鍛造、冷間抽伸や切削などの加工によって所定の寸法に成形されることが多い。
【０００３】
したがって、近年、上記の工程の省略や材料歩留りの向上を目的に、寸法公差が±０．２０ｍｍ以内の所謂「精密圧延材」に対する要求が極めて大きくなっている。なお、ここでいう寸法公差とは、製品公称直径に対し許容できる上下限の範囲を意味する。
【０００４】
精密圧延材は、一般に、製品サイズ毎に圧延機のロールを組替えた３ロール圧延機や４ロール圧延機を仕上げ圧延機に用いて製造されてきた。しかし、種々のサイズの精密圧延材の需要が増加しているなかで、各サイズ毎にロールを組替えることは、生産性の低下につながる。更に、ロール数が増加することで資材費や整備費が増加してコストも嵩んでしまう。そのため、製品サイズ毎にロール組替えを行わなくても精密圧延材を圧延することが可能な技術が待望されている。
【０００５】
生産性の向上やコストの低減を目的に、製品サイズに合わせたロール組替えを必要としない所謂「フリーサイズ圧延」に関する技術が、例えば、特開平７−２６５９０４号公報に開示されている。この公報で提案された「棒線材のフリーサイズ圧延方法」は、円形素材から３パスの３ロール圧延機で棒線材を仕上げる際に、「１パス目のロールカリバー（ロール孔型）を素材の円の直径と同一以上の円弧、又は直線と適当な逃がしとを配した形状とし、２パス目及び３パス目のロールカリバーを素材の円の直径に対し９５％ないし同一の直径の円弧と適当な逃がしとを配した形状とする」ことで、素材直径ないし素材直径の８０％の範囲内でフリーサイズ圧延をする技術である。
【０００６】
しかし、前記公報で提案された技術は、仕上げ圧延機群に入る素材の直径を基に３パスのカリバー形状を決定するものである。このため、仕上げ圧延機群としての３ロール圧延機に到るまでの張力バランスの崩れや素材長手方向の温度バラツキによって、３ロール圧延機に入る直前の素材寸法に大きな変動が生じる場合など、圧延の条件によっては最終製品の寸法精度が悪化して寸法公差が±０．２０ｍｍ以内の精密圧延が困難な場合もあった。
【０００７】
【発明が解決しようとする課題】
本発明は、上記現状に鑑みなされたもので、その目的は、製品サイズ毎にロール組替えを行わなくても、噛み出しを生ずることなく寸法公差が±０．２０ｍｍ以内の所謂「精密圧延材」を安定して確実に得ることが可能な、断面形状が円形の棒鋼及び線材の精密圧延方法を提供することにある。
【０００８】
【課題を解決するための手段】
本発明の要旨は、下記に示す棒鋼及び線材の精密圧延方法にある。
【０００９】
すなわち、「３本のロールの軸線延長が垂直面内で形成する正三角形の傾きを６０°違えて配置させた３台の３ロール仕上げ圧延機及び、前記３台の３ロール圧延機の上流側に位置する１台以上の２ロール圧延機を用いる、断面形状が円形の棒鋼及び線材の精密圧延方法であって、仕上げ圧延機群を構成する３ロール圧延機のうち、最も上流側の３ロール圧延機の直前に位置する２ロール圧延機のロール孔型形状を製品公称直径に対して１．０〜１．３倍の直径の円弧と角度５〜２０゜での逃がしとを配した形状、上流側から２台目及び３台目の３ロール圧延機のロール孔型形状をそれぞれ製品公称直径に対して１．０〜１．２倍の直径の円弧と角度５〜４０゜での逃がしとを配した形状とし、仕上げ圧延機群の圧延機における圧下をそれぞれ独立に選択して圧延することを特徴とする棒鋼及び線材の精密圧延方法。」である。
【００１０】
なお、「角度５〜２０゜での逃がしを配する」、「角度５〜４０゜での逃がしを配する」とは、図１に示すように、隣接する孔型間の中心線に対して角度θが５〜２０゜、５〜４０゜の範囲で孔型円弧を逃がすことをいう。図１の（ａ）、（ｂ）はそれぞれ３ロール圧延機と２ロール圧延機のロール孔型を示すもので、角度φの部分の孔型形状は単一直径の円弧からなり、角度θの「逃がし」の部分の孔型形状は上記角度φの部分の円弧より直径の大きな単一又は複数の円弧又は／及び直線からなるものである。
【００１１】
圧延機の圧下を独立して選択するには、例えば各圧延機ごとに圧下のための圧延ロールギャップと周速とを決定すればよい。
【００１２】
２ロール圧延機は、これを複数台用いる場合には、２本のロールの軸線延長が垂直面内で形成する直線の傾きを９０°違えて配置させた２ロール圧延機群とするのがよい。
【００１３】
本発明者らは、製品サイズ毎にロール組替えを行わなくても噛み出しを生ずることなく、しかも安定して確実に精密圧延材を得ることが可能な断面形状が円形の棒鋼及び線材の圧延方法に関し、２ロール圧延機及び、仕上げ圧延機群としての３台の３ロール圧延機とを用いて種々の検討を重ねた。その結果、下記の知見を得た。
【００１４】
（ａ）最終製品の寸法精度は、仕上げ圧延機群における最も下流の（すなわち上流側から３台目の）３ロール圧延機及びその１つ手前の３ロール圧延機のロール孔型形状により決定される。
【００１５】
（ｂ）上記（ａ）から精密圧延のためには、仕上げ圧延機群における最も下流の３ロール圧延機及びその１つ手前の３ロール圧延機のロール孔型の形状を、製品公称直径と同一の直径の円弧とすることが望ましい。
【００１６】
（ｃ）製品サイズ毎にロール組替えを行わなくてもよい、すなわちフリーサイズ圧延を行うためには、仕上げ圧延機群における最も下流の３ロール圧延機及びその１つ手前の３ロール圧延機のロール孔型の形状を、製品公称直径に対してある程度余裕のある直径の円弧としておけばよい。
【００１７】
（ｄ）仕上げ圧延機群の最も上流の３ロール圧延機に入る直前での素材寸法変動を抑えておけば、安定且つ確実に精密圧延材を得ることができる。
【００１８】
（ｅ）仕上げ圧延機群である３ロール圧延機の直前に位置する２ロール圧延機の孔型形状を規定することで、仕上げ圧延機群の最も上流の３ロール圧延機に入る直前での素材寸法変動を抑制することができる。
【００１９】
本発明は、上記の知見に基づいて完成されたものである。
【００２０】
【発明の実施の形態】
以下、本発明の各要件について詳しく説明する。
【００２１】
図２に製品と孔型形状との関係を示すように、最終製品の寸法精度は、仕上げ圧延機群における最も下流の（すなわち上流側から３台目の）３ロール圧延機及び、その１つ手前の（すなわち上流側から２台目の）３ロール圧延機のロール孔型形状により決定される。なお、図２の（ａ）は公称直径がＤの製品、（ｂ）は最も下流の（すなわち上流側から３台目の）３ロール圧延機の直径がＤ（３）のロール孔型、（ｃ）は上流側から２台目の３ロール圧延機の直径がＤ（２）のロール孔型である。又、同図（ｄ）は仕上げ圧延機群である３ロール圧延機の直前に位置する２ロール圧延機の直径がｄのロール孔型である。
【００２２】
この図２からも明らかなように、極めて精密な圧延を行うためには、最も下流の３ロール圧延機及び、その１つ手前の３ロール圧延機のロール孔型の形状を、製品の公称直径と同一の直径の円弧とすることが望ましい。しかし、上記２台の３ロール圧延機のロール孔型の形状を、製品の公称直径と同一の直径の円弧とした場合には、製品サイズ毎にロール組替えを行う必要が生ずる。そこで、本発明においては、製品サイズ毎にロール組替えを行わなくてもよいように、すなわちフリーサイズ圧延が可能となるように、最も下流となる上流側から３台目の３ロール圧延機及び、その１つ手前となる上流側から２台目の３ロール圧延機のロール孔型の形状を、製品公称直径に対して１．０〜１．２倍の直径の円弧と角度５〜４０゜での逃がしとを配した形状の余裕を持たせたものとした。
【００２３】
前記した各３ロール圧延機のロール孔型の形状が製品公称直径に対して１．０倍未満の場合には、寸法公差の「−０．２０ｍｍ」を外れる（すなわち、製品公称直径に対し許容できる下限値を外れる）ことがあり、一方、１．２倍を超える場合には、寸法公差の「＋０．２０ｍｍ」を外れる（すなわち、製品公称直径に対し許容できる上限値を外れる）ことがある。又、図１に示すような逃がしの角度（以下、逃げ角ということもある）θが５゜未満の場合には「噛み出し」を生ずることがあり、一方、θが４０゜を超えると寸法公差外れをきたすことがある。
【００２４】
したがって、本発明においては、前記２台の３ロール圧延機のロール孔型の形状を、それぞれ製品公称直径に対して１．０〜１．２倍の直径の円弧と角度５〜４０゜での逃がしとを配した形状に規定した。
【００２５】
本発明においては、更に、仕上げ圧延機群である３ロール圧延機の圧下をそれぞれ独立して選択する。仕上げ圧延機群を構成する３ロール圧延機における圧下をそれぞれ独立して選択するのは、各圧延機での圧延によって発生する張力変化が解消できるからである。この仕上げ圧延機群である３ロール圧延機での圧下をそれぞれ独立して選択するためには、例えば各圧延機ごとに圧下のための圧延ロールギャップと周速とを決定すればよい。
【００２６】
本発明においては、仕上げ圧延機群の最も上流の３ロール圧延機のロール孔型形状は、大きな減面率を確保できて以降の圧延機で噛み出しを生じず、更にフリーサイズ圧延が容易となるように、製品公称直径に対して１．０〜３．０倍の直径の円弧と角度０〜４０゜での逃がしとを配した形状とすることが好ましい。
【００２７】
ここで、角度が０゜の逃がし（つまり、逃げ角が０゜）とは逃がしを設けないことを意味する。
【００２８】
本発明おいては、仕上げ圧延機群としての３ロール圧延機のうちで最も上流に位置する３ロール圧延機に入る直前での素材寸法変動を抑えて安定且つ確実に精密圧延材を得るために、前記３ロール圧延機の直前に位置する２ロール圧延機のロール孔型形状を、製品公称直径に対して１．０〜１．３倍の直径の円弧と角度５〜２０゜での逃がしとを配した形状とする。
【００２９】
前記した２ロール圧延機のロール孔型の形状が製品公称直径に対して１．０倍未満の場合には、寸法公差の「−０．２０ｍｍ」を外れる（すなわち、製品公称直径に対し許容できる下限値を外れる）ことがあり、一方、１．３倍を超える場合には、寸法公差の「＋０．２０ｍｍ」を外れる（すなわち、製品公称直径に対し許容できる上限値を外れる）ことがある。
【００３０】
又、仕上げ圧延機群としての３ロール圧延機に到るまでの張力バランスの崩れや素材長手方向の温度バラツキによって、３ロール圧延機に入る直前の素材寸法に大きな変動が生じた場合、２ロール圧延機のロール孔型形状に関する図１に示すような逃がしの角度が５゜未満の場合には部分的に噛み出しが発生する場合があるし、一方、角度が２０゜を超える場合にはたとえ仕上げ圧延機群である３ロール圧延機のロール孔型形状等を規定しても寸法変動が大きくなって所望の寸法公差が±０．２０ｍｍ以内の精密圧延材が得られない場合がある。
【００３１】
したがって、本発明においては、前記２ロール圧延機のロール孔型の形状を、製品公称直径に対して１．０〜１．３倍の直径の円弧と角度５〜２０゜での逃がしとを配した形状に規定した。
【００３２】
本発明においては、１台以上の２ロール圧延機で圧延した後、３台の３ロール圧延機からなる仕上げ圧延機群で圧延を行うが、仕上げ圧延機群の前に何台の２ロール圧延機を用いるかは、素材の寸法と製品の寸法とから適宜決定すればよい。例えば、素材に直径が１８０ｍｍ程度のビレットを用いて直径が５０ｍｍ程度の製品に仕上げる場合には１２台程度の２ロール圧延機を用いればよいし、素材に直径が６０ｍｍ程度のビレットを用いて直径が５０ｍｍ程度の製品に仕上げる場合には１台の２ロール圧延機を用いればよい。
【００３３】
以下、実施例により本発明を詳しく説明する。
【００３４】
【実施例】
表１に示すＪＩＳのＳ４５Ｃ相当の化学組成を有する断面が１８０ｍｍ×１８０ｍｍの鋼片を１０００〜１２５０℃に加熱してから、１２００〜９００℃の温度で直径（製品公称直径）が３０．０ｍｍ、５０．０ｍｍ及び７０．０ｍｍの丸棒に熱間圧延した。なお、仕上げ圧延機群には３本のロールの軸線延長が垂直面内で形成する正三角形の傾きを６０°違えて配置させた３ロール圧延機を３台用い、前記各３ロール圧延機ごとに圧下のための圧延ロールギャップと周速とを決定して仕上げ圧延を行った。又、前記３台の３ロール圧延機の上流側には２本のロールの軸線延長が垂直面内で形成する直線の傾きを９０°違えて配置させた１４台の２ロール圧延機を用いた。
【００３５】
【表１】
表２〜４に、製品公称直径、仕上げ圧延機群に入る前の被圧延材の直径（ｍｍ）、仕上げ圧延機群に入る直前の被圧延材の放射温度計で測定した長手方向での温度バラツキの最大値（℃）、一番上流の３ロール圧延機の直前に位置する２ロール圧延機のロール孔型形状及び、上流側から１台目〜３台目の３ロール圧延機のロール孔型形状をまとめて示す。なお、表２〜４において、Ｄは製品の公称直径、ｄは前記２ロール圧延機のロール孔型の直径であり、Ｄ（１）、Ｄ（２）及びＤ（３）はそれぞれ上流側から１台目、２台目及び３台目の３ロール圧延機のロール孔型の直径である。
【００３７】
【表２】
【表３】
【表４】
仕上げ圧延後、直径（製品公称直径）が３０．０ｍｍ、５０．０ｍｍ及び７０．０ｍｍの丸棒について、目視又は磁粉探傷装置によって噛み出しの有無をチェックするとともに、マイクロメータを用いて偏径差、すなわち、同一断面における直径の最大値と最小値との差を測定した。偏径差が０．４０ｍｍ以下の場合、目標とする寸法公差で±０．２０ｍｍ以内の精密圧延が達成されたことになる。表５に、上記の各調査結果をまとめて示す。
【００４１】
【表５】
表５から、本発明に係る方法で仕上げ圧延した試験番号１、８〜１０、１７〜１９、２６及び２７の場合には、偏径差が０．４０ｍｍ以下で、寸法公差±０．２０ｍｍの精密圧延を満足できることが明らかである。又、上流から１台目の３ロール圧延機のロール孔型の直径を製品公称直径に対して１．０〜３．０倍の直径の円弧と角度０〜４０゜での逃がしとを配した形状とすることで、フリーサイズ圧延にも容易に対応できることが明らかである。
なお、仕上げ圧延機群に入る直前の被圧延材の長手方向での温度バラツキを１００℃以下とすることで一層偏径差が小さくなり、更なる精密圧延が可能となることがわかる。
【００４３】
これに対して、本発明の規定から外れた方法で仕上げ圧延した試験番号２〜７、１１〜１６及び２０〜２５の場合には、▲１▼噛み出しが生じる、▲２▼偏径差が０．４０ｍｍを超える（すなわち、寸法公差が±０．２０ｍｍを超える）のいずれかに該当している。
【００４４】
【発明の効果】
本発明の棒鋼及び線材の精密圧延方法によれば、製品サイズ毎にロール組替えを行わなくても、噛み出しを生ずることなく寸法公差が±０．２０ｍｍ以内の所謂「精密圧延材」を得ることができるので産業上の効果は大きい。
【図面の簡単な説明】
【図１】ロール孔型形状の「逃がし」について説明する図であり、（ａ）は３ロール圧延機の場合、（ｂ）は２ロール圧延機の場合である。
【図２】製品と２ロール、３ロールの圧延機の孔型形状との関係を示す図で、（ａ）は公称直径がＤの製品、（ｂ）は最も下流に位置する上流側から３台目の３ロール圧延機の直径がＤ（３）のロール孔型、（ｃ）は上流側から２台目の３ロール圧延機の直径がＤ（２）のロール孔型、（ｄ）は仕上げ圧延機群である３ロール圧延機の直前に位置する２ロール圧延機の直径がｄのロール孔型である。
【符号の説明】
Ｄ：製品の公称直径、
Ｄ（３）：上流側から３台目の３ロール圧延機のロール孔型の直径、
Ｄ（２）：上流側から２台目の３ロール圧延機のロール孔型の直径、
ｄ：３ロール圧延機の直前に位置する２ロール圧延機のロール孔型の直径。
θ：逃がしの角度[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for precision rolling of steel bars and wire rods, and in particular, biting with high dimensional accuracy using one or more two-roll rolling mills and three three-roll rolling mills constituting a finishing rolling mill group. The present invention relates to a rolling method for obtaining a steel bar and a wire rod having a circular cross-sectional shape without causing any problems.
[0002]
[Prior art]
Hot-rolled steel bars and wires are usually subjected to soft annealing and spheroidizing annealing, and are then formed into predetermined dimensions by processing such as cold forging, cold drawing and cutting.
[0003]
Therefore, in recent years, the demand for so-called “precision rolled material” having a dimensional tolerance within ± 0.20 mm has been greatly increased for the purpose of omitting the above steps and improving the material yield. In addition, the dimension tolerance here means the range of the upper and lower limits allowable for the product nominal diameter.
[0004]
In general, precision rolled materials have been manufactured by using a three-roll rolling mill or a four-roll rolling mill in which the rolls of the rolling mill are rearranged for each product size as a finishing rolling mill. However, when the demand for precision rolled materials of various sizes is increasing, changing the rolls for each size leads to a decrease in productivity. Furthermore, the increase in the number of rolls increases material costs and maintenance costs, and increases costs. Therefore, there is a need for a technique that can roll a precision rolled material without changing the roll for each product size.
[0005]
For the purpose of improving productivity and reducing costs, a technique related to so-called “free size rolling” that does not require roll change in accordance with the product size is disclosed in, for example, Japanese Patent Application Laid-Open No. 7-265904. The “free-size rolling method for bar wire” proposed in this publication is that when a bar wire is finished from a circular material with a three-pass three-roll rolling mill, a “roll caliber (roll hole type) for the first pass is used as the material circle. The shape of a circular arc that is equal to or greater than the diameter of the straight line, or a straight line and an appropriate relief, and the second and third pass roll calibers are suitable for an arc having a diameter of 95% or the same diameter as the circle of the material. It is a technology that performs free size rolling within the range of the material diameter or 80% of the material diameter by making it a shape with relief.
[0006]
However, the technique proposed in the above publication determines the three-pass caliber shape based on the diameter of the material entering the finish rolling mill group. For this reason, when there is a large variation in the material dimensions immediately before entering the 3-roll mill due to the collapse of the tension balance until reaching the 3-roll mill as the finish rolling mill group or the temperature variation in the longitudinal direction of the material, etc. Depending on the above conditions, the dimensional accuracy of the final product may deteriorate, and precision rolling with a dimensional tolerance within ± 0.20 mm may be difficult.
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described situation, and the purpose thereof is a so-called “precision rolled material” having a dimensional tolerance of ± 0.20 mm or less without causing biting without changing rolls for each product size. It is an object to provide a method for precision rolling of a steel bar and a wire having a circular cross-sectional shape that can stably and reliably be obtained.
[0008]
[Means for Solving the Problems]
The gist of the present invention resides in the following method for precision rolling of steel bars and wires.
[0009]
That is, “the upstream side of the three three-roll rolling mills and the three three-roll rolling mills in which the inclination of the equilateral triangle formed by the extension of the three rolls in the vertical plane is different by 60 °. Is a precision rolling method for steel bars and wire rods having a circular cross-section using one or more two-roll rolling mills positioned at the same position, and among the three-roll rolling mills constituting the finishing rolling mill group, the most upstream three rolls A roll hole shape of a two-roll rolling mill located immediately before the rolling mill in which a circular arc having a diameter of 1.0 to 1.3 times the nominal diameter of the product and a relief at an angle of 5 to 20 ° are arranged, The roll hole shape of the second and third three-roll rolling mills from the upstream side is an arc of 1.0 to 1.2 times the nominal diameter of the product and the relief at an angle of 5 to 40 °. Each of the rolling reductions in the finishing mills Precision rolling method of steel bars and wire rods, characterized by rolling by independently selected. "It is.
[0010]
In addition, as shown in FIG. 1, “arrange a relief at an angle of 5 to 20 °” and “arrange an escape at an angle of 5 to 40 °” with respect to the center line between adjacent hole types. This means that the circular arc is released when the angle θ is in the range of 5 to 20 ° or 5 to 40 °. (A) and (b) of FIG. 1 show the roll hole molds of a 3-roll mill and a 2-roll mill, respectively, and the hole shape of the angle φ portion consists of a single-diameter arc, and the angle θ The hole shape of the “relief” portion is composed of a single arc or a plurality of arcs and / or straight lines having a diameter larger than the arc of the angle φ portion.
[0011]
In order to independently select the rolling reduction of the rolling mill, for example, a rolling roll gap and a peripheral speed for rolling reduction may be determined for each rolling mill.
[0012]
In the case of using a plurality of two-roll rolling mills, it is preferable to use a two-roll rolling mill group in which the inclinations of the straight lines formed by the axial extensions of the two rolls in the vertical plane are different by 90 °. .
[0013]
The present inventors have provided a method for rolling a steel bar and a wire rod having a circular cross-sectional shape that does not cause biting without having to change rolls for each product size, and that can stably and reliably obtain a precision rolled material. In connection with this, various studies were repeated using a two-roll mill and three three-roll mills as a finishing mill group. As a result, the following knowledge was obtained.
[0014]
(A) The dimensional accuracy of the final product is determined by the roll hole shape of the three-roll rolling mill that is the most downstream (that is, the third unit from the upstream side) in the group of finish rolling mills and the three-roll rolling mill that is just before that. The
[0015]
(B) For precision rolling from (a) above, the shape of the roll hole mold of the most downstream three-roll rolling mill in the finishing rolling mill group and the three-roll rolling mill just before it is the same as the product nominal diameter. It is desirable to use an arc having a diameter of.
[0016]
(C) It is not necessary to change rolls for each product size, that is, in order to perform free size rolling, the most downstream three-roll rolling mill in the finishing rolling mill group and the roll hole of the three-roll rolling mill just before it The shape of the mold may be an arc having a diameter with a certain margin with respect to the product nominal diameter.
[0017]
(D) Precise rolled material can be obtained stably and reliably by suppressing the material dimension fluctuation immediately before entering the most upstream three-roll mill in the finishing mill group.
[0018]
(E) By defining the hole shape of a two-roll mill located just before the three-roll mill that is the finishing mill group, the material immediately before entering the three-roll mill at the most upstream of the finishing mill group Dimensional variation can be suppressed.
[0019]
The present invention has been completed based on the above findings.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, each requirement of the present invention will be described in detail.
[0021]
As shown in FIG. 2, the dimensional accuracy of the final product is the most downstream (that is, the third unit from the upstream side) three-roll rolling mill and one of them. It is determined by the roll hole shape of the three-roll mill in front (that is, the second unit from the upstream side). 2A is a product having a nominal diameter of D, FIG. 2B is a roll hole type having a diameter of D (3) of the most downstream (that is, the third unit from the upstream side) three-roll rolling mill, c) is a roll hole type in which the diameter of the second three-roll rolling mill from the upstream side is D (2). FIG. 4D shows a roll hole type having a diameter d of a two-roll rolling mill located immediately before a three-roll rolling mill which is a group of finish rolling mills.
[0022]
As is apparent from FIG. 2, in order to perform extremely precise rolling, the shape of the roll hole mold of the most downstream 3-roll rolling mill and the immediately preceding three-roll rolling mill is set to the nominal diameter of the product. It is desirable to make it the circular arc of the same diameter. However, when the shape of the roll hole mold of the two three-roll rolling mills is an arc having the same diameter as the nominal diameter of the product, it is necessary to change the roll for each product size. Therefore, in the present invention, the third three-roll rolling mill from the upstream side that is the most downstream so that it is not necessary to change the roll for each product size, that is, to enable free size rolling, and its The shape of the roll hole mold of the second three-roll rolling mill from the upstream side, which is one before, is an arc of 1.0 to 1.2 times the nominal diameter of the product and an angle of 5 to 40 °. It was assumed that there was room for the shape of the relief.
[0023]
When the shape of the roll hole mold of each of the above-mentioned three-roll rolling mills is less than 1.0 times the product nominal diameter, the dimensional tolerance of “−0.20 mm” is deviated (ie, allowable for the product nominal diameter). May exceed the upper limit of the product nominal diameter, and may exceed the allowable tolerance of the product nominal diameter. . Further, when the relief angle (hereinafter also referred to as the relief angle) θ as shown in FIG. 1 is less than 5 °, “biting” may occur. On the other hand, when θ exceeds 40 °, the dimension It may be out of tolerance.
[0024]
Therefore, in the present invention, the shape of the roll hole mold of the two three-roll rolling mills is 1.0 to 1.2 times the diameter of the product nominal diameter and an angle of 5 to 40 °. It was defined as a shape with relief.
[0025]
In the present invention, the reduction of the three-roll rolling mill which is the finish rolling mill group is selected independently. The reason why the reduction in the three-roll rolling mills constituting the finishing rolling mill group is independently selected is that tension changes generated by rolling in each rolling mill can be eliminated. In order to independently select the reduction in the three-roll rolling mill that is the finish rolling mill group, for example, the rolling roll gap and the peripheral speed for reduction may be determined for each rolling mill.
[0026]
In the present invention, the roll hole shape of the three-roll rolling mill at the most upstream of the finish rolling mill group can secure a large reduction in area and does not cause biting in subsequent rolling mills, and further facilitates free size rolling. As described above, it is preferable to have a shape in which an arc having a diameter of 1.0 to 3.0 times the nominal diameter of the product and a relief at an angle of 0 to 40 ° are arranged.
[0027]
Here, a relief with an angle of 0 ° (that is, a relief angle of 0 °) means that no relief is provided.
[0028]
In the present invention, in order to obtain a precision rolled material stably and reliably by suppressing the material dimension fluctuation immediately before entering the three-roll rolling mill located at the most upstream among the three-roll rolling mills as the finishing rolling mill group. The roll hole shape of the two-roll mill located immediately before the three-roll mill is an arc of 1.0 to 1.3 times the nominal diameter of the product and a relief at an angle of 5 to 20 °. The shape is arranged.
[0029]
If the shape of the roll hole mold of the above-mentioned two-roll mill is less than 1.0 times the product nominal diameter, the dimensional tolerance of “−0.20 mm” will be deviated (ie, acceptable for the product nominal diameter). On the other hand, when the ratio exceeds 1.3 times, the dimensional tolerance “+0.20 mm” may be exceeded (that is, an allowable upper limit value may be exceeded for the product nominal diameter).
[0030]
Also, if the material size immediately before entering the 3-roll mill is greatly changed due to the loss of tension balance until reaching the 3-roll mill as the finishing mill group or the temperature variation in the longitudinal direction of the material, the 2-roll When the relief angle is less than 5 ° as shown in FIG. 1 relating to the roll hole shape of the rolling mill, biting may occur partially, while when the angle exceeds 20 °, Even if the roll hole shape and the like of a three-roll mill, which is a group of finish rolling mills, are specified, the dimensional variation increases, and a precision rolled material with a desired dimensional tolerance within ± 0.20 mm may not be obtained.
[0031]
Therefore, in the present invention, the shape of the roll hole mold of the two-roll rolling mill is arranged with an arc having a diameter of 1.0 to 1.3 times the nominal diameter of the product and a relief at an angle of 5 to 20 °. The shape was defined.
[0032]
In the present invention, after rolling with one or more two-roll rolling mills, rolling is performed with a finish rolling mill group consisting of three three-roll rolling mills. Whether to use the machine may be appropriately determined from the dimensions of the material and the dimensions of the product. For example, when a billet with a diameter of about 180 mm is used as a material to finish a product with a diameter of about 50 mm, about 12 two-roll rolling mills may be used, and the material is used with a billet with a diameter of about 60 mm. Is finished with a product of about 50 mm, a single two-roll rolling mill may be used.
[0033]
Hereinafter, the present invention will be described in detail by way of examples.
[0034]
【Example】
After heating a steel piece having a cross section of 180 mm × 180 mm having a chemical composition equivalent to JIS S45C shown in Table 1 to 1000 to 1250 ° C., the diameter (product nominal diameter) is 30.0 mm at a temperature of 1200 to 900 ° C., Hot rolled to 50.0 mm and 70.0 mm round bars. In addition, in the finishing rolling mill group, three 3-roll rolling mills in which the inclinations of equilateral triangles formed by extending the axes of the three rolls in the vertical plane are different by 60 ° are used, and each of the three-roll rolling mills is used. Finally, finish rolling was performed by determining the rolling roll gap and peripheral speed for reduction. Further, on the upstream side of the three three-roll rolling mills, 14 two-roll rolling mills were used in which the inclinations of the straight lines formed in the vertical plane by the axial extensions of the two rolls were different by 90 °. .
[0035]
[Table 1]
Tables 2 to 4 show the product nominal diameter, the diameter (mm) of the rolled material before entering the finish rolling mill group, and the temperature in the longitudinal direction measured by a radiation thermometer of the rolled material immediately before entering the finishing rolling mill group. Maximum variation (° C.), roll hole shape of a two-roll mill located immediately before the most upstream three-roll mill, and roll holes of the first to third three-roll mills from the upstream side The mold shape is shown together. In Tables 2 to 4, D is the nominal diameter of the product, d is the diameter of the roll hole mold of the two-roll rolling mill, and D (1), D (2), and D (3) are respectively from the upstream side. This is the diameter of the roll hole type of the first, second and third three-roll rolling mills.
[0037]
[Table 2]
[Table 3]
[Table 4]
After finish rolling, round bars with diameters (product nominal diameters) of 30.0 mm, 50.0 mm, and 70.0 mm are checked for biting by visual inspection or using a magnetic particle flaw detector, and a difference in diameter is detected using a micrometer. That is, the difference between the maximum value and the minimum value of the diameter in the same cross section was measured. When the deviation in diameter is 0.40 mm or less, the precision rolling within ± 0.20 mm is achieved with the target dimensional tolerance. Table 5 summarizes the results of each of the above investigations.
[0041]
[Table 5]
From Table 5, in the case of test numbers 1, 8 to 10, 17 to 19, 26, and 27 that were finish-rolled by the method according to the present invention, the deviation in diameter was 0.40 mm or less and the dimensional tolerance was ± 0.20 mm. It is clear that precision rolling can be satisfied. The diameter of the roll hole mold of the first three-roll rolling mill from the upstream is 1.0 to 3.0 times larger than the nominal diameter of the product and a relief at an angle of 0 to 40 °. It is apparent that the shape can easily cope with free size rolling.
In addition, it turns out that an uneven diameter difference becomes still smaller by making the temperature variation in the longitudinal direction of the material to be rolled immediately before entering the finishing rolling mill group 100 ° C. or less, and further precision rolling becomes possible.
[0043]
On the other hand, in the case of
[0044]
【The invention's effect】
According to the precision rolling method for steel bars and wire rods of the present invention, a so-called “precision rolled material” having a dimensional tolerance within ± 0.20 mm without biting can be obtained without changing rolls for each product size. Therefore, the industrial effect is great.
[Brief description of the drawings]
FIGS. 1A and 1B are diagrams for explaining a “relief” of a roll hole shape, in which FIG. 1A shows a case of a three-roll mill, and FIG. 1B shows a case of a two-roll mill.
FIG. 2 is a diagram showing the relationship between a product and the hole shape of a 2-roll and 3-roll rolling mill, (a) is a product having a nominal diameter of D, and (b) is 3 from the upstream side located on the most downstream side. The diameter of the first three-roll rolling mill is D (3) roll hole type, (c) is the roll hole type of the second three-roll rolling mill having the diameter D (2) from the upstream side, (d) is A two-roll mill located in front of a three-roll mill that is a group of finish rolling mills is a roll hole mold having a diameter d.
[Explanation of symbols]
D: nominal diameter of the product,
D (3): diameter of the roll hole mold of the third three-roll rolling mill from the upstream side,
D (2): Diameter of the roll hole mold of the second three-roll rolling mill from the upstream side,
d: Diameter of the roll hole mold of the two-roll mill located immediately before the three-roll mill.
θ: Escape angle
Claims (1)
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001227634A JP3606825B2 (en) | 2001-07-27 | 2001-07-27 | Precision rolling method for steel bars and wire rods |
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|---|---|---|---|
| JP2001227634A JP3606825B2 (en) | 2001-07-27 | 2001-07-27 | Precision rolling method for steel bars and wire rods |
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| JP2003039102A JP2003039102A (en) | 2003-02-12 |
| JP3606825B2 true JP3606825B2 (en) | 2005-01-05 |
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| CN103286126B (en) * | 2013-06-08 | 2015-10-07 | 中冶赛迪工程技术股份有限公司 | The rolling mill practice of the few frame final shaping unit unit of high-speed rod combined type |
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