JP2008246520A - Method of manufacturing steel bar or wire rod - Google Patents
Method of manufacturing steel bar or wire rod Download PDFInfo
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Description
本発明は、断面形状が略正方形の角鋼材をタンデム圧延機を用いて粗圧延し、その後さらに圧延を続けることにより棒鋼または線材を製造する方法に関するものである。 The present invention relates to a method of manufacturing a bar steel or a wire rod by roughly rolling a square steel material having a substantially square cross-sectional shape using a tandem rolling mill and then continuing the rolling.
棒鋼や線材は、断面形状が略正方形の角鋼材を、タンデム圧延機を用いて粗圧延し、その後さらに圧延を続けることにより製造される。例えば、断面形状が円形の丸棒鋼は、断面形状が略正方形の角鋼材をタンデム圧延機で圧延することにより製造できることが特許文献1に既に提案されている。即ち、まず、断面形状が略正方形の角鋼材を製造し、この角鋼材に表面疵が発生しているかどうかを、例えば磁紛探傷機を用いて調査する。角鋼材を製造する過程(例えば、分塊圧延など)で、表面疵が発生することがあるからである。表面疵が発生していないことを確認した角鋼材は、圧延方向が互いに直交するスタンドを交互に並べたタンデム圧延機によって粗圧延し、その後、中間圧延と仕上げ圧延を行なうことにより丸棒鋼を製造できる。一方、表面疵が認められた角鋼材については、疵がひどい場合は、スクラップとして廃棄処分するが、疵が軽度である場合は、角鋼材の表面を研削して表面疵を除去してからタンデム圧延を行なう。このように角鋼材をタンデム圧延して丸棒鋼を製造する途中過程を図面を用いて説明する。 Steel bars and wire rods are manufactured by roughly rolling a square steel bar having a substantially square cross-sectional shape using a tandem rolling mill and then continuing the rolling. For example, Patent Document 1 has already proposed that a round steel bar having a circular cross-sectional shape can be manufactured by rolling a square steel material having a substantially square cross-sectional shape with a tandem rolling mill. That is, first, a square steel material having a substantially square cross-sectional shape is manufactured, and whether or not surface flaws are generated in the square steel material is examined using, for example, a magnetic flaw detector. This is because surface flaws may occur in the process of manufacturing a square steel material (for example, ingot rolling). Square steel that has been confirmed to have no surface flaws is roughly rolled by a tandem rolling mill in which stands that are orthogonal to each other in the rolling direction are arranged, and then round bar steel is manufactured by performing intermediate rolling and finish rolling. it can. On the other hand, square steel materials with surface defects are discarded as scrap if the defects are severe, but if the defects are mild, the surface defects are removed by grinding the surface of the square steel material and then tandem. Roll. An intermediate process of producing a round bar steel by tandem rolling a square steel material in this way will be described with reference to the drawings.
図1は、角鋼材をタンデム圧延しているときの様子を示した図であり、角鋼材11が、タンデム圧延ロール21a〜21cで圧延されているときの様子を、角鋼材11の末端側から見たときの図を示している。圧延ロール21a〜21cは、タンデム圧延機を構成するスタンドに取り付けられており、圧延ロール21aと21cは、圧延方向が垂直方向(天地方向)となるように、圧延ロール21bは、圧延方向が水平方向となるように配置されている。なお、図1では、タンデム圧延機中の3機の圧延ロール21a〜21cについて示したが、圧延ロールの数はこれに限定されるものではない。 FIG. 1 is a diagram illustrating a state in which a square steel material is being tandem-rolled, and a state in which the square steel material 11 is being rolled by tandem rolling rolls 21 a to 21 c is illustrated from the end side of the square steel material 11. The figure when it sees is shown. The rolling rolls 21a to 21c are attached to a stand that constitutes a tandem rolling mill, and the rolling rolls 21a and 21c have a horizontal rolling direction such that the rolling direction is a vertical direction (vertical direction). It is arranged to be in the direction. Although FIG. 1 shows three rolling rolls 21a to 21c in the tandem rolling mill, the number of rolling rolls is not limited to this.
圧延ロール21a〜21cの全周には、みぞ状の孔型(カリバー)が設けられており、粗圧延工程では、カリバーの形状が菱カリバーの圧延ロール21a〜21cを用いて(a)→(b)→(c)の順で、角鋼材11を垂直方向からと水平方向から粗圧延することにより、角鋼材11の断面形状が、角形→横方向に偏平した菱形→縦方向に偏平した菱形→横方向に偏平した菱形と繰返し変形し(11a→11b→11c)、粗圧延では断面積が小さくなった角鋼材が得られる。次いで、断面積が小さくなった角鋼材を、中間圧延工程では、角カリバーかオーバルカリバーが設けられた圧延ロールを用いてタンデム圧延を行なうことで、断面形状が、角形からオーバル形状へ変形し、断面積が小さくなったオーバル状鋼材が得られる。そして、仕上げ圧延工程では、オーバルカリバーか丸カリバーが設けられた圧延ロールを用いてタンデム圧延を行なうことで、断面形状が、オーバル→丸→オーバル→丸と繰り返し変形し、断面積が小さくなった丸棒鋼を製造できる。 Groove-shaped hole shapes (calibers) are provided on the entire circumference of the rolling rolls 21a to 21c, and in the rough rolling process, the rolling rolls 21a to 21c whose caliber has a diamond caliber are used (a) → ( b) → Roughly rolling the square steel material 11 from the vertical direction and the horizontal direction in the order of (c), so that the cross-sectional shape of the square steel material 11 is a rhombus flattened in a square → lateral direction → a rhombus flattened in a vertical direction → Repetitively deformed with a rhombus flattened in the horizontal direction (11a → 11b → 11c), and rough rolling yields a square steel material having a reduced cross-sectional area. Next, the square steel material having a reduced cross-sectional area is subjected to tandem rolling using a rolling roll provided with a square caliber or an oval caliber in the intermediate rolling process, so that the cross-sectional shape is deformed from a square shape to an oval shape, An oval steel material having a reduced cross-sectional area is obtained. And in the finish rolling process, by performing tandem rolling using a rolling roll provided with oval caliber or round caliber, the cross-sectional shape was repeatedly deformed from oval → round → oval → round, and the cross-sectional area was reduced. Round steel bar can be manufactured.
ところがタンデム圧延して得られる丸棒鋼には、表面に線状の疵が発生することがあった。そこでタンデム圧延して得られた丸棒鋼は、表面疵が発生していないか再度調査し、表面疵が発生していないことが認められたもののみが製品として出荷される。 However, in the round bar steel obtained by tandem rolling, linear wrinkles may occur on the surface. Therefore, round steel bars obtained by tandem rolling are examined again for surface flaws, and only those found to have no surface flaws are shipped as products.
こうして出荷された製品は、適当な長さに切断された後、例えば、鍛造して所望の製品に加工される。ところが表面疵探傷して疵が認められず、製品として出荷された丸棒鋼であっても、製品形状に鍛造すると表面に線状の疵が発生することがあった。この疵の深さは、最大で2.0mm程度にまで達することがあった。
本発明の目的は、断面形状が略正方形の角鋼材をタンデム圧延して棒鋼または線材を製造するに当たり、表面疵の発生を防止でき、しかも得られた棒鋼または線材を鍛造しても表面に線状の疵が発生しない棒鋼または線材を製造できる方法を提供することにある。 The object of the present invention is to prevent the occurrence of surface flaws when producing a steel bar or wire by tandem rolling a square steel material having a substantially square cross-sectional shape. It is an object of the present invention to provide a method capable of producing a steel bar or a wire that does not generate a wrinkle.
上記課題を解決することのできた本発明に係る棒鋼または線材の製造方法とは、圧延方向が互いに直交するスタンドを交互に並べたタンデム圧延機によって、断面形状が略正方形の角鋼材を粗圧延し、その後さらに圧延を続けることにより棒鋼または線材を製造する方法であって、粗圧延前に、前記角鋼材の断面について2組の対辺の距離を夫々測定し、それらの距離の差が所定値を超える場合には、該距離の差が所定値以下となるように角鋼材の表面を研削してからタンデム圧延する点に要旨を有する。 The method for producing a steel bar or wire according to the present invention that has solved the above-mentioned problems is to roughly roll a square steel material having a substantially square cross-sectional shape by a tandem rolling machine in which stands whose rolling directions are orthogonal to each other are alternately arranged. The method of manufacturing a steel bar or a wire rod by continuing further rolling after that, before rough rolling, measure the distance between two pairs of opposite sides of the cross section of the square steel material, and the difference between the distances is a predetermined value. In the case of exceeding, the gist is in that tandem rolling is performed after grinding the surface of the square steel material so that the difference in distance is not more than a predetermined value.
具体的には、断面形状が略正方形の角鋼材を製造する工程(工程1)、前記角鋼材の表面疵探傷を行なう工程(工程2)、前記工程2で発見された表面疵を、角鋼材表面を研削することによって除去する工程(工程3)、前記工程3の後、角鋼材の断面について、2組の対辺の距離を夫々測定し、それらの距離の差を算出する工程(工程4)、前記距離の差が所定値を超える場合には、該距離の差が所定値以下となるように角鋼材表面を研削する工程(工程5)、前記距離の差が所定値以下になっている角鋼材をタンデム圧延する工程(工程6)、を含んで操業すればよい。 Specifically, a step of producing a square steel material having a substantially square cross-sectional shape (Step 1), a step of performing surface flaw detection on the square steel material (Step 2), and a surface flaw found in Step 2 are used as a square steel material. A step of removing the surface by grinding (step 3), and a step of measuring the distance between two pairs of opposite sides of the section of the square steel material after the step 3 and calculating a difference between the distances (step 4). When the difference in distance exceeds a predetermined value, the step of grinding the square steel surface so that the difference in distance is equal to or less than the predetermined value (step 5), the difference in distance is equal to or less than the predetermined value. What is necessary is just to operate including the process (process 6) of carrying out the tandem rolling of a square steel material.
本発明によれば、断面形状が略正方形の角鋼材をタンデム圧延機で粗圧延する前に、角鋼材の断面形状が適切な形状であるかどうかをチェックし、所定の形状になっていない角鋼材は、所定の形状になるように表面を研削してから粗圧延しているため、粗圧延後に中間圧延と仕上げ圧延を行なって得られた棒鋼または線材には、折れ込み疵が発生しておらず、またこの棒鋼または線材を鍛造しても表面に線状の疵が発生しない棒鋼または線材を製造できる。なお、以下では、棒鋼または線材のうち、特に丸棒鋼を中心に説明するが、本発明は丸棒鋼に限定されるものではない。 According to the present invention, before roughly rolling a square steel material having a substantially square cross section with a tandem rolling mill, it is checked whether or not the cross sectional shape of the square steel material is an appropriate shape, and the corner that is not in a predetermined shape. Since the steel material is roughly rolled after the surface is ground so as to have a predetermined shape, the bar steel or wire obtained by performing intermediate rolling and finish rolling after the rough rolling has creases. In addition, it is possible to manufacture a bar or wire that does not generate linear wrinkles on the surface even if this bar or wire is forged. In the following description, among the steel bars or wire rods, description will be made mainly on round steel bars, but the present invention is not limited to round steel bars.
本発明者らは、断面形状が略正方形の角鋼材をタンデム圧延して得られた丸棒鋼(製品)を表面疵探傷したときに表面疵が認められなかったにもかかわらず、この丸棒鋼を鍛造したときに疵が発生する原因について検討を重ねた。その結果、圧延ロールに角鋼材が適切に保持されないために、角鋼材のコーナー部が圧延ロールによって展伸され、展伸された部分(耳)が、次の圧延ロールと接触することで角鋼材側に折り込まれる現象が発生することが判明した。このように鋼材の一部が折り込まれ、この状態のまま圧延が進むと、折り込まれた部分(耳)が鋼材と密着して一体となるため、最終的に得られた丸棒鋼を表面探傷しても表面疵は発見できないと考えられる。角鋼材のコーナー部が展伸され、この伸びた部分がこのままの状態で圧延ロールに噛み込み、角鋼材本体側に折り込まれて角鋼材と一体になる現象を、以下では鋼返りと呼ぶ。 The present inventors have used this round bar steel even though no surface flaws were observed when a round bar steel (product) obtained by tandem rolling a square steel material having a substantially square cross section was detected. The cause of flaws during forging was studied repeatedly. As a result, since the square steel material is not properly held by the rolling roll, the corner portion of the square steel material is expanded by the rolling roll, and the expanded portion (ear) comes into contact with the next rolling roll so that the square steel material is It was found that the phenomenon of folding into the side occurred. When a part of the steel material is folded in this way and rolling proceeds in this state, the folded part (ears) are brought into close contact with the steel material, so that the round bar steel finally obtained is subjected to surface flaw detection. However, it is thought that surface defects cannot be found. The phenomenon in which the corner portion of the square steel material is stretched, the stretched portion is held in this state in the rolling roll, is folded into the square steel material main body side, and is integrated with the square steel material is hereinafter referred to as steel return.
鋼返りが発生するときの様子を図面を用いて説明する。図2は、鋼返りが発生するときの様子を模式的に示した図である。上記図1と対応する部分には、同じ符号を付した。 A state when steel return occurs will be described with reference to the drawings. FIG. 2 is a diagram schematically showing a state in which steel return occurs. Parts corresponding to those in FIG. 1 are given the same reference numerals.
工程(a)で垂直方向に圧延された角鋼材は、工程(b)で水平方向に圧延されるが、このとき角鋼材11bのコーナー部(端部)が展伸され、この展伸部分13が工程(c)で角鋼材11c側に折り込まれ、線14で示すように巻き込まれる。この状態のまま圧延が進むと、折り込まれた部分(耳)14は、角鋼材の外壁面として一体となる。 The square steel material rolled in the vertical direction in the step (a) is rolled in the horizontal direction in the step (b). At this time, the corner portion (end portion) of the square steel material 11b is extended, and this extended portion 13 is expanded. Is folded to the square steel material 11c side in the step (c), and is wound up as shown by the line 14. When rolling proceeds in this state, the folded portion (ear) 14 becomes an integrated outer wall surface of the square steel material.
このように鋼返りが発生しても、通常、折り込まれた部分が線状の疵となるため、粗圧延して得られた角鋼材を中間圧延と仕上げ圧延して得られた丸棒鋼の表面疵探傷を行なうと、線状の疵が認められ、鋼返りが発生していることが判明する。そのため線状の疵が認められる丸棒鋼は、スクラップとして廃棄処分される。 Even if steel return occurs in this way, since the folded portion usually becomes a linear flaw, the surface of the round bar steel obtained by intermediate rolling and finish rolling a square steel material obtained by rough rolling When flaw detection is performed, linear wrinkles are recognized and it is found that steel return has occurred. For this reason, round steel bars with linear wrinkles are discarded as scrap.
ところが、粗圧延時に鋼返りが発生しても、展伸された部分が鋼材の外壁に折り込まれて鋼材と一体になると、仕上げ圧延して得られた丸棒鋼の表面には線状の疵が認められないときがある。即ち、疵の間口が狭く、外壁面に沿って斜めに折れ込むと、表面疵探傷を行なっても疵信号レベルが低下し、発見されないと考えられる。そのため表面に線状の疵が認められない丸棒鋼は、鋼返りが発生しているにもかかわらず、製品として出荷されることがあった。ところがこの製品を鍛造すると、折り込まれた部分が開放され、線状疵を発生するのである。 However, even if steel return occurs during rough rolling, if the stretched part is folded into the outer wall of the steel material and integrated with the steel material, the surface of the round bar steel obtained by finish rolling has linear wrinkles. There are times when it is not allowed. That is, if the front edge of the wrinkle is narrow and bends diagonally along the outer wall surface, the wrinkle signal level is lowered even if surface flaw detection is performed, and it is considered that it is not detected. For this reason, round steel bars in which no linear wrinkles are observed on the surface are sometimes shipped as products despite the occurrence of steel return. However, when this product is forged, the folded portion is released and linear wrinkles are generated.
そこで本発明者らは、角鋼材をタンデム圧延機で粗圧延するときに鋼返りが発生するのを防止するために検討を重ねてきた。その結果、タンデム圧延機で粗圧延を行なう前における角鋼材の断面形状が適切であるかどうかをチェックし、所定の形状になっていない角鋼材については表面を研削して所定の形状に調整してから圧延すれば、粗圧延時に鋼返りが発生するのを防止できることを見出し、本発明を完成した。以下、本発明を完成するに至った経緯を説明しつつ本発明の特徴部分について説明する。 Therefore, the present inventors have repeatedly studied in order to prevent the occurrence of steel turning when the square steel material is roughly rolled with a tandem rolling mill. As a result, it is checked whether or not the cross-sectional shape of the square steel material is appropriate before rough rolling with a tandem rolling mill, and the square steel material that is not in the predetermined shape is ground to adjust it to the predetermined shape. The present invention was completed by finding that steel rolling can be prevented from occurring during rough rolling if rolling is performed thereafter. Hereafter, the characteristic part of this invention is demonstrated, explaining the process which came to complete this invention.
本発明者らは、圧延に供する角鋼材の断面形状に着目し、長手方向に対して垂直な断面の形状が略正方形の鋼材を用意し、この断面形状を変化させた後、タンデム圧延して鋼返りが発生するかどうか実験を行った。用意した角鋼材は、断面形状が略正方形の角鋼材である。この角鋼材の断面の模式図を図3に示す。図3に示すように、角鋼材の各辺をA〜Dとし、各コーナー部をa〜dとする。 The inventors pay attention to the cross-sectional shape of the square steel material used for rolling, prepare a steel material having a substantially square cross-sectional shape with respect to the longitudinal direction, change the cross-sectional shape, and then perform tandem rolling. An experiment was conducted to determine whether steel return occurred. The prepared square steel material is a square steel material having a substantially square cross-sectional shape. A schematic diagram of the cross section of this square steel material is shown in FIG. As shown in FIG. 3, each side of the square steel material is A to D, and each corner portion is a to d.
まず、鋼返りが発生する原因は、角鋼材のコーナー部の形状にあるのではないかと考え、コーナー部a〜dを図3に点線で示すように研削して供試材を作製し、この供試材をタンデム圧延機で粗圧延した。供試材は2種作製し、このうち供試材1は、角鋼材のコーナー部を15Cとなるように研削したもの、供試材2は、25Cとなるように研削したものを作製した。なお、角鋼材の断面は、155.2mm×155.0mmの正方形であった。なお、15Cとは、図4に示すように、コーナー部を研削したときに、1辺が角から15mm研削されている状態を意味する。また、25Cとは、同様に、1辺が角から25mm研削されている状態を意味する。 First, it is thought that the cause of the steel return is the shape of the corner portion of the square steel material, and the corner portions a to d are ground as shown by dotted lines in FIG. The test material was roughly rolled with a tandem rolling mill. Two types of test materials were prepared, among which sample material 1 was prepared by grinding the corner portion of a square steel material to 15C, and sample material 2 was prepared by grinding to 25C. In addition, the cross section of the square steel material was a square of 155.2 mm × 155.0 mm. As shown in FIG. 4, 15C means a state in which one side is ground 15 mm from the corner when the corner portion is ground. Similarly, 25C means a state where one side is ground 25 mm from the corner.
次に、角鋼材のコーナー部を研削すると共に、角鋼材の2面を研削して供試材を2種作製し、夫々粗圧延を行なった。このうち供試材3は、断面が154.7mm×154.4mmの角鋼材を、上記供試材1と同様にコーナー部を15Cに研削した後、1組の対辺(図3の辺Bと辺D)の距離が151.3mmになるように研削した。一方、供試材4は、断面が154.8mm×155.3mmの角鋼材を、上記供試材2と同様にコーナー部を25Cに研削した後、1組の対辺(図3に示した辺Bと辺D)の距離が148.4mmとなるように研削した。 Next, the corner portion of the square steel material was ground, and the two surfaces of the square steel material were ground to produce two types of test materials, which were each subjected to rough rolling. Of these, the test material 3 was prepared by grinding a square steel material having a cross section of 154.7 mm × 154.4 mm to a corner portion of 15 C in the same manner as the test material 1, and then a pair of opposite sides (the side B in FIG. 3). Grinding was performed so that the distance of side D) was 151.3 mm. On the other hand, the specimen 4 was prepared by grinding a square steel material having a cross section of 154.8 mm × 155.3 mm to a corner portion of 25 C in the same manner as the specimen 2 above, and then a pair of opposite sides (the sides shown in FIG. 3). Grinding was performed so that the distance between B and side D) was 148.4 mm.
辺Aと辺Cの距離をx、辺Bと辺Dの距離をyとすると、2組の対辺の距離の差(x−y)は、供試材3については3.5mm、供試材4については6.2mmであった。 If the distance between side A and side C is x, and the distance between side B and side D is y, the difference in distance between the two pairs of opposite sides (xy) is 3.5 mm for specimen 3 and the specimen. 4 was 6.2 mm.
次に、角鋼材のコーナー部を研削すると共に、角鋼材の4面を研削して断面積を小さくした供試材を2種作製し、夫々粗圧延を行なった。このうち供試材5は、断面が154.7mm×154.2mmの角鋼材を、上記供試材1と同様にコーナー部を15Cに研削した後、全辺(図3の辺A〜辺D)を研削した。即ち、辺Aと辺Cの距離が152.7mm、辺Bと辺Dの距離が151.9mmになるように研削した。一方、供試材6は、断面が154.9mm×154.4mmの角鋼材を、上記供試材2と同様にコーナー部を25Cに研削した後、全辺(図3の辺A〜辺D)を研削した。即ち、辺Aと辺Cの距離が151.8mm、辺Bと辺Dの距離が151.1mmになるように研削した。 Next, while grinding the corner part of a square steel material, 2 types of test materials which made the cross-sectional area small by grinding 4 surfaces of a square steel material were each rough-rolled. Of these, the test material 5 was prepared by grinding a square steel material having a cross section of 154.7 mm × 154.2 mm into a corner portion of 15 C in the same manner as the test material 1, and then all sides (side A to side D in FIG. 3). ). That is, grinding was performed so that the distance between side A and side C was 152.7 mm, and the distance between side B and side D was 151.9 mm. On the other hand, the test material 6 was prepared by grinding a square steel material having a cross section of 154.9 mm × 154.4 mm to a corner portion of 25 C in the same manner as the test material 2 and then all sides (side A to side D in FIG. 3). ). That is, grinding was performed so that the distance between side A and side C was 151.8 mm, and the distance between side B and side D was 151.1 mm.
辺Aと辺Cの距離をx、辺Bと辺Dの距離をyとすると、2組の対辺の距離の差(x−y)は、供試材5については0.8mm、供試材6については0.7mmであった。 When the distance between side A and side C is x, and the distance between side B and side D is y, the difference in distance between two pairs (xy) is 0.8 mm for specimen 5, 6 was 0.7 mm.
比較対象として、コーナー部を研削しない場合についても同様に実験を行なった。即ち、用意した角鋼材(供試材7)をそのままタンデム圧延機で粗圧延した。鋼材の断面は、155.0mm×155.0mmの正方形であった。 As a comparison object, the same experiment was performed when the corner portion was not ground. That is, the prepared square steel material (test material 7) was roughly rolled as it was with a tandem rolling mill. The cross section of the steel material was a 155.0 mm × 155.0 mm square.
次に、角鋼材の2面を研削して供試材を2種作製し、夫々粗圧延を行なった。このうち供試材8は、断面が155.8mm×152.1mmの角鋼材を、1組の対辺(図3の辺Aと辺C)の距離が155.5mmになるように研削した。一方、供試材9は、断面が155.2mm×154.8mmの角鋼材を、1組の対辺(図3に示した辺Bと辺D)の距離が149.5mmとなるように研削した。 Next, two types of test materials were prepared by grinding two surfaces of the square steel material, and each was roughly rolled. Among them, the specimen 8 was a square steel material having a cross section of 155.8 mm × 152.1 mm, which was ground so that the distance between one pair of opposite sides (side A and side C in FIG. 3) was 155.5 mm. On the other hand, the test material 9 was a square steel material having a cross section of 155.2 mm × 154.8 mm and was ground so that the distance between one pair of opposite sides (side B and side D shown in FIG. 3) was 149.5 mm. .
辺Aと辺Cの距離をx、辺Bと辺Dの距離をyとすると、2組の対辺の距離の差(x−y)は、供試材8については3.4mm、供試材9については5.7mmであった。 When the distance between side A and side C is x, and the distance between side B and side D is y, the difference in distance between the two pairs of opposite sides (xy) is 3.4 mm for specimen 8 and the specimen. 9 was 5.7 mm.
次に、角鋼材の4面を研削して断面積を小さくした供試材を作製し、粗圧延を行なった。供試材10は、断面が155.3mm×154.9mmの角鋼材を、全辺(図3の辺A〜辺D)を研削した。即ち、辺Aと辺Cの距離が152.6mm、辺Bと辺Dの距離が151.0mmになるように研削した。辺Aと辺Cの距離をx、辺Bと辺Dの距離をyとすると、2組の対辺の距離の差(x−y)は、供試材10については1.6mmであった。 Next, a sample material having a reduced cross-sectional area was prepared by grinding four surfaces of a square steel material, and rough rolling was performed. The specimen 10 was prepared by grinding a square steel material having a cross section of 155.3 mm × 154.9 mm on all sides (side A to side D in FIG. 3). That is, grinding was performed so that the distance between side A and side C was 152.6 mm, and the distance between side B and side D was 151.0 mm. When the distance between the side A and the side C is x and the distance between the side B and the side D is y, the difference in distance between the two pairs of opposite sides (xy) was 1.6 mm for the test material 10.
各供試材について、表面研削前における角鋼材の各辺の長さ、2組の対辺の距離の差、表面研削後におけるコーナー部の研削量、角鋼材の各辺の長さ、2組の対辺の距離の差を下記表1に示す。また、粗圧延時における鋼返りの発生の有無についても下記表1に示した。 For each specimen, the length of each side of the square steel material before surface grinding, the difference in the distance between two sets of opposite sides, the amount of grinding of the corner part after surface grinding, the length of each side of the square steel material, The difference in distance between opposite sides is shown in Table 1 below. The presence or absence of steel return during rough rolling is also shown in Table 1 below.
表1から次のように考察できる。供試材1〜2と供試材7から明らかなように、角鋼材のコーナー部を研削しても粗圧延時に鋼返りは発生しなかった。従って鋼返りが発生する原因は、コーナー部の形状にはないことが分かる。供試材5〜6と供試材10に示すように、角鋼材の断面の全面を研削して断面積を小さくしても粗圧延時に鋼返りは発生しなかった。 From Table 1, it can be considered as follows. As is clear from the test materials 1 and 2 and the test material 7, even when the corner portion of the square steel material was ground, no steel return occurred during rough rolling. Therefore, it is understood that the cause of the steel return is not in the shape of the corner portion. As shown in the test materials 5 to 6 and the test material 10, even when the entire cross-section of the square steel material was ground to reduce the cross-sectional area, no steel return occurred during rough rolling.
一方、供試材3や供試材8のように、角鋼材の断面について、1組の対辺を研削した場合に、2組の対辺の距離の差(x−y)が3.5mm(供試材3)や3.4mm(供試材8)であれば、粗圧延時に鋼返りは発生しなかった。 On the other hand, when one set of opposite sides is ground with respect to the cross section of the square steel material as in the specimen 3 and the specimen 8, the distance difference (xy) between the two sets of opposite sides is 3.5 mm (provided) In the case of Sample 3) or 3.4 mm (Sample 8), no steel return occurred during rough rolling.
これに対し、供試材4や供試材9のように、角鋼材の断面について、1組の対辺を研削した場合であっても、2組の対辺の距離の差(x−y)が6.2mm(供試材4)や5.7mm(供試材9)であれば、粗圧延時に鋼返りが発生することが判明した。 On the other hand, even when one set of opposite sides is ground with respect to the cross section of the square steel material like the sample material 4 and the sample material 9, there is a difference in distance (xy) between the two sets of opposite sides. It was found that steel return occurs during rough rolling when the thickness is 6.2 mm (sample 4) or 5.7 mm (sample 9).
以上の実験結果から、鋼返りが発生する原因は、角鋼材のコーナー部の形状や、角鋼材の断面積ではなく、2組の対辺の距離の差が影響を及ぼしていると考えられる。鋼返りの発生に、タンデム圧延に供する角鋼材の断面形状が影響を及ぼしているのは、タンデム圧延時に次のような現象が起こっているからであると考えられる。即ち、上記供試材4や供試材9のように、粗圧延する直前の角鋼材の断面形状が、表面疵を除去するため行った表面研削によって長方形になり、2組の対辺の距離(x−y)が大きくなると、角鋼材の外壁面のうち圧延ロールに保持されない面が出てくるため、圧延が進むに連れて、角鋼材が回転すると考えられる。これを図1と図2を用いて説明する。 From the above experimental results, it is considered that the cause of the steel return is not the shape of the corner portion of the square steel material or the cross-sectional area of the square steel material, but the difference in the distance between the two pairs of opposite sides. The reason why the cross-sectional shape of the square steel material used for tandem rolling has an influence on the occurrence of steel return is thought to be because the following phenomenon occurs during tandem rolling. That is, like the test material 4 and the test material 9, the cross-sectional shape of the square steel material just before rough rolling becomes a rectangle by surface grinding performed to remove surface defects, and the distance between two sets of opposite sides ( When xy) becomes large, a surface that is not held by the rolling roll comes out of the outer wall surface of the square steel material, and it is considered that the square steel material rotates as rolling progresses. This will be described with reference to FIGS.
図1の工程(b)に点線で示した角鋼材12は、圧延ロール21bで圧延される直前の角鋼材の位置を示しており、図2の工程(b)に点線で示した角鋼材14は、圧延ロール21bで圧延される直前の角鋼材の位置を示している。2組の対辺距離の差(x−y)が小さく、断面が略正方向の角鋼材をタンデム圧延すると、図1の工程(a)に示すように、角鋼材11aの全面が圧延ロール21aに保持されるため、該角鋼材11aが次の圧延ロール21bに到達するまでの間に、角鋼材11aは回転しない。そのため該角鋼材12を圧延ロール21bで圧延すると、角鋼材12の4面が圧延ロール21bに保持されつつ圧延される。 The square steel material 12 indicated by the dotted line in the step (b) of FIG. 1 indicates the position of the square steel material immediately before being rolled by the rolling roll 21b, and the square steel material 14 indicated by the dotted line in the step (b) of FIG. Indicates the position of the square steel material immediately before being rolled by the rolling roll 21b. When a square steel material having a small difference (xy) between two sets of opposite side distances and a substantially positive cross section is tandem-rolled, as shown in step (a) of FIG. 1, the entire surface of the square steel material 11a is applied to the rolling roll 21a. Since it is held, the square steel material 11a does not rotate until the square steel material 11a reaches the next rolling roll 21b. Therefore, when the square steel material 12 is rolled by the rolling roll 21b, the four surfaces of the square steel material 12 are rolled while being held by the rolling roll 21b.
これに対し、2組の対辺距離の差(x−y)が大きく、断面が長方形の角鋼材をタンデム圧延すると、図2の工程(a)に示すように、角鋼材11aは圧延ロール21aに均一に保持されず、保持されている面と保持されていない面が発生する。そのため角鋼材11aは、不安定な状態となり、次の圧延ロール21bに到達するまでに回転し、圧延ロール21bでは、回転した状態の角鋼材14が強制的に圧延される。そのため角鋼材11bのコーナー部が延伸され、この状態のまま次の圧延ロール21cに供給されると、延伸されたコーナー部13が折り込まれてしまう。 On the other hand, when the square steel material having a large difference (xy) between the two sets of opposite sides and having a rectangular cross section is tandem-rolled, as shown in step (a) in FIG. It is not uniformly held, and a held surface and a non-held surface are generated. Therefore, the square steel material 11a is in an unstable state and rotates before reaching the next rolling roll 21b, and the rolled steel bar 14 is forcibly rolled in the rolling roll 21b. Therefore, when the corner portion of the square steel material 11b is stretched and supplied to the next rolling roll 21c in this state, the stretched corner portion 13 is folded.
以上の通り、タンデム圧延機を用いて角鋼材から丸棒鋼を製造する際に、タンデム圧延機に供給する前記角鋼材の断面について2組の対辺の距離を夫々測定し、それらの距離の差(x−y)が所定値を超える場合には、該距離の差が所定値以下となるように角鋼材の表面を研削してからタンデム圧延を行なえば、鋼返りの発生を防止できると考えられる。なお、上記では角鋼材から丸棒鋼を製造する過程を中心に説明したが、本発明で製品として製造する形態は丸棒鋼に限定されるものではなく、角棒鋼であってもよいし、六角鋼等であってもよい。また、棒鋼に限定されるものでもなく、線材であってもよい。 As mentioned above, when manufacturing round bar steel from a square steel material using a tandem rolling mill, the distance of two sets of opposite sides is measured about the section of the square steel material supplied to a tandem rolling mill, and the difference of those distances ( When xy) exceeds a predetermined value, it is considered that the occurrence of steel return can be prevented by performing tandem rolling after grinding the surface of the square steel material so that the difference in distance is equal to or less than the predetermined value. . In addition, although demonstrated above centering on the process which manufactures a round bar steel from a square steel material, the form manufactured as a product by this invention is not limited to a round bar steel, A square bar steel may be sufficient, and a hexagonal steel Etc. Moreover, it is not limited to a steel bar but may be a wire rod.
所定値とは、タンデム圧延機に応じて予め定められた値であり、例えば、圧延データを解析して定めることができる。即ち、タンデム圧延前の角鋼材の断面について、2組の対辺の距離の差を算出した後、タンデム圧延して棒鋼または線材を製造する。得られた棒鋼または線材について、表面疵探傷を行ない、表面疵が認められなかった棒鋼または線材について鍛造を行ない、鍛造しても表面疵が発生しなかったときの前記距離の差を当該タンデム圧延機における所定値とすればよい。 The predetermined value is a value determined in advance according to the tandem rolling mill, and can be determined by analyzing rolling data, for example. That is, after calculating the difference between the distances between the two sets of opposite sides of the cross section of the square steel material before tandem rolling, the steel bar is produced by tandem rolling. The obtained bar steel or wire is subjected to surface flaw detection, the bar steel or wire without surface flaw is forged, and the difference in the distance when no surface flaw occurs even after forging is determined by tandem rolling. What is necessary is just to set it as the predetermined value in a machine.
タンデム圧延しているときに鋼返りが発生しているかどうかは、圧延ロールに備えられているモーターに電流変動計を設け、電流の変動を測定して確認してもよい。鋼返りが発生しない場合は、角鋼材のコーナー部が展伸されて折れ込みが発生しないため、角鋼材の断面形状が極端に変化していない。そのため圧延ロールに備えられたモーターに供給される電流は、ほぼ一定となり、例えば、約800Aを維持する。しかし鋼返りが発生すると、角鋼材の断面形状が極端に変化し、表面に凹凸ができるため、圧延ロールに負荷がかかり、該圧延ロールに備えられたモーターに供給される電流が変動する。このとき電流は、例えば、約1260Aにまで高くなる。従って定常状態に対して、電流の上昇が発生した場合には、鋼返りが発生したと確認できる。 Whether or not steel return has occurred during tandem rolling may be confirmed by providing a current fluctuation meter in a motor provided in the rolling roll and measuring fluctuations in current. When the steel return does not occur, the corner portion of the square steel material is expanded and no folding occurs, so that the cross-sectional shape of the square steel material does not change extremely. Therefore, the electric current supplied to the motor provided in the rolling roll becomes substantially constant, for example, maintains about 800A. However, when steel return occurs, the cross-sectional shape of the square steel material changes extremely, and the surface is uneven, so that a load is applied to the rolling roll, and the current supplied to the motor provided in the rolling roll fluctuates. At this time, the current increases to, for example, about 1260A. Therefore, when an increase in current occurs with respect to the steady state, it can be confirmed that steel return has occurred.
タンデム圧延機に供給する前記角鋼材の断面について2組の対辺の距離を夫々測定したときに、それらの距離の差(x−y)が所定値を超える原因は、製造して得られた角鋼材に表面疵が発生しているかどうかを調査したときに、表面疵が認められた角鋼材のうち疵が軽度である場合に角鋼材の表面を研削して表面疵を除去することにより、断面が長方形になる点にあると考えられる。 When the distance between two pairs of opposite sides of the section of the square steel material supplied to the tandem rolling mill is measured, the difference between the distances (xy) exceeds the predetermined value. When investigating whether or not surface flaws occur in the steel material, if the flaws are mild among the square steel materials with surface flaws, the surface of the square steel material is ground to remove the surface flaws. Is considered to be at a point that becomes a rectangle.
そこで表面疵を除去するときは、具体的には、以下の手順で操業すれば、表面疵がなく、しかも熱間圧延しても表面疵が発生しない棒鋼または線材を製造できる。即ち、断面形状が略正方形の角鋼材を製造し(工程1)、得られた角鋼材の表面疵探傷を行ない(工程2)、前記工程2で表面疵が発見された場合には、該表面疵を角鋼材の表面を研削することによって除去する(工程3)。そして本発明では、前記工程3の後、角鋼材の断面について2組の対辺の距離を夫々測定し、それらの距離の差を算出し(工程4)、前記距離の差が所定値を超える場合には、該距離の差が所定値以下となるように角鋼材表面を研削する(工程5)。次に、工程6で、前記距離の差が所定値以下になっている角鋼材をタンデム圧延すれば、所望の棒鋼または線材を製造できる。以下、各工程について詳細に説明する。 Therefore, when removing surface defects, specifically, by operating according to the following procedure, it is possible to produce a steel bar or wire that has no surface defects and does not generate surface defects even when hot rolled. That is, a square steel material having a substantially square cross section is manufactured (step 1), surface flaw detection is performed on the obtained square steel material (step 2), and when surface flaws are found in step 2, The wrinkles are removed by grinding the surface of the square steel material (step 3). And in this invention, after the said process 3, the distance of two sets of opposite sides is each measured about the cross section of a square steel material, the difference of those distances is calculated (process 4), and the difference of the said distance exceeds predetermined value First, the surface of the square steel material is ground so that the difference in distance is not more than a predetermined value (step 5). Next, in Step 6, a desired steel bar or wire can be manufactured by tandem rolling a square steel material in which the difference in distance is equal to or less than a predetermined value. Hereinafter, each step will be described in detail.
[工程1]
工程1では、断面形状が略正方形の角鋼材を製造する。この角鋼材の製造方法は特に限定されず、常法に従って、連続鋳造または分塊圧延によって得られるビレット等を意味する。角鋼材(ビレット)は、長手方向に対して垂直面の断面形状が略正方形であればよく、鋼材の一辺の長さは、100〜250mm程度であればよい。略正方形とは、角鋼材の断面について直交する辺の長さの差が、長い方の辺の長さに対して4%程度以内であることを意味する。
[Step 1]
In step 1, a square steel material having a substantially square cross-sectional shape is manufactured. The manufacturing method of this square steel material is not particularly limited, and means a billet or the like obtained by continuous casting or ingot rolling according to a conventional method. The square steel material (billet) may have a substantially square cross-sectional shape in the vertical direction with respect to the longitudinal direction, and the length of one side of the steel material may be about 100 to 250 mm. The term “substantially square” means that the difference between the lengths of the sides perpendicular to the cross section of the square steel material is within about 4% of the length of the longer side.
[工程2]
工程2では、常法に従って、上記工程1で得られた角鋼材の表面疵探傷を行ない、角鋼材の表面に疵が発生しているかどうかを検査する。表面疵探傷は、例えば、磁紛探傷法で行なえばよい。
[Step 2]
In step 2, according to a conventional method, the surface flaw detection of the square steel material obtained in the above step 1 is performed to inspect whether flaws are generated on the surface of the square steel material. The surface flaw detection may be performed by, for example, a magnetic particle inspection method.
表面疵探傷を行なうときには、通常、内部疵探傷も行なう。内部疵探傷は、例えば、超音波探傷を行なえばよい。内部疵探傷を行なって内部疵が見つかった場合には、スクラップとして廃棄する。 When surface flaw detection is performed, internal flaw detection is usually performed. For the internal flaw detection, for example, ultrasonic flaw detection may be performed. If internal flaws are found after internal flaw detection, they are discarded as scrap.
表面疵探傷を行なって表面疵が認められず、内部疵探傷を行なって内部疵も発見できなかった場合には、そのままタンデム圧延を行なえばよい(後述する工程6)。 If surface flaw detection is performed and no surface flaws are observed, and internal flaw detection is not performed and internal flaws are not found, tandem rolling may be performed as it is (step 6 described later).
一方、内部疵探傷を行なっても内部疵は発見できないが、表面疵探傷を行なって表面疵が認められた場合には、この表面疵が大きく、深く、表面研削で除去できない程度であれば、角鋼材をスクラップとして廃棄する。しかし表面疵が小さく、深さが浅いときには、通常、表面研削して表面疵を除去する(工程3)。 On the other hand, internal flaws cannot be found even if internal flaw detection is performed, but if surface flaws are detected and surface flaws are observed, if this surface flaw is large and deep and cannot be removed by surface grinding, Discard the square steel as scrap. However, when the surface flaw is small and the depth is shallow, the surface flaw is usually removed by surface grinding (step 3).
[工程3]
上述したように、工程2で表面疵が見つかり、この表面疵が小さく、深さが浅いときには、工程3で、角鋼材の表面を研削して表面疵を除去する。このとき表面疵が少ない場合には、疵の部分を局所的にチッピングして切削除去すればよいが、表面疵が多い場合には、通常、表面疵が認められた面において表面疵を全て含むように、角鋼材の幅方向に向かってグラインダーにて全面研削を行なう。ところがこの全面研削を行なうと、角鋼材の断面が長方形に変形してしまう。
[Step 3]
As described above, when a surface defect is found in step 2 and the surface defect is small and the depth is shallow, in step 3, the surface of the square steel material is ground to remove the surface defect. At this time, if the surface flaws are small, the portion of the wrinkles may be locally chipped and removed, but if there are many surface flaws, usually all the surface flaws are included in the surface where the surface flaws are recognized. Thus, the whole surface is ground with a grinder in the width direction of the square steel material. However, when this entire surface grinding is performed, the section of the square steel material is deformed into a rectangle.
そこで本発明では、工程3で表面疵を除去した後は、工程4として、角鋼材の断面について2組の対辺の距離を夫々測定し、続く工程5では、それらの距離の差が所定値を超える場合には、該距離の差が所定値以下となるように角鋼材の表面を研削してからタンデム圧延を行なう。 Therefore, in the present invention, after removing surface flaws in Step 3, as Step 4, the distances between two sets of opposite sides are measured for the cross section of the square steel material, and in the following Step 5, the difference between the distances becomes a predetermined value. When exceeding, the surface of the square steel material is ground so that the difference in distance is not more than a predetermined value, and then tandem rolling is performed.
[工程4]
工程4では、角鋼材の断面について2組の対辺の距離を夫々測定し、それらの距離の差を算出する。2組の対辺の距離とは、上記図3の辺Aと辺Cの距離xと、辺Bと辺Dの距離yを意味し、それらの距離の差とはx−yを意味する。
[Step 4]
In step 4, the distance between two sets of opposite sides is measured for the cross section of the square steel material, and the difference between the distances is calculated. The distance between the two pairs of opposite sides means the distance x between the sides A and C in FIG. 3 and the distance y between the sides B and D, and the difference between the distances means xy.
2組の対辺の距離を測定する位置は、角鋼材の先端近傍か、角鋼材の末端近傍とすればよい。角鋼材の先端近傍や末端近傍は、第n番目の圧延ロールを通過して次の第n+1番目の圧延ロールに到達するまでの間で、圧延ロールに保持されず、フリーな状態となるため、回転し易く、鋼返りを発生し易いからである。 The position for measuring the distance between the two sets of opposite sides may be near the tip of the square steel material or near the end of the square steel material. The vicinity of the tip and the end of the square steel material is not held by the rolling roll until it passes through the nth rolling roll and reaches the next n + 1th rolling roll, and is in a free state. It is because it is easy to rotate and easily generates steel return.
ここで先端近傍と末端近傍とは、タンデム圧延機のうち粗圧延用に設けられたスタンド間距離に相当する領域を意味する。即ち、粗圧延用に設けられたスタンドについて、隣り合うスタンド間距離を夫々測定し、これらの距離の中で最大の距離を決定する。この決定された距離に相当する位置を、角鋼材の先端または末端から測定し、先端または末端からこの決定された位置までの領域について、角鋼材の断面について2組の対辺の距離を測定すればよい。 Here, the vicinity of the front end and the vicinity of the end mean a region corresponding to a distance between stands provided for rough rolling in the tandem rolling mill. That is, for the stands provided for rough rolling, the distance between adjacent stands is measured, and the maximum distance among these distances is determined. If the position corresponding to the determined distance is measured from the tip or end of the square steel material, and the distance from the tip or end to the determined position is measured by measuring the distance between two pairs of opposite sides of the cross section of the square steel material Good.
上記工程3で、角鋼材の複数箇所について表面研削を実施した場合であって、該表面研削を行なった位置が角鋼材の先端近傍か末端近傍に複数箇所存在するときは、2組の対辺の距離の差が最大となる位置における差の値に基づいて判断すればよい。 In the above step 3, when surface grinding is performed on a plurality of locations of a square steel material, and there are a plurality of locations where the surface grinding is performed near the front end or the end of the square steel material, two sets of opposite sides What is necessary is just to judge based on the value of the difference in the position where the difference of distance becomes the maximum.
なお、角鋼材の断面について2組の対辺の距離を夫々測定する時期は、表面研削終了後であって、角鋼材を加熱炉に装入して加熱を行なうまでの間とする。 It should be noted that the time for measuring the distance between the two pairs of opposite sides of the cross section of the square steel material is after the end of the surface grinding and until the square steel material is charged in the heating furnace and heated.
[工程5]
工程5では、上記工程4において算出した距離の差(x−y)に基づいて、該距離の差が所定値を超える場合には、該距離の差が所定値以下となるように角鋼材表面を研削する。なお、前記距離の差が所定値以下の場合には、表面研削を行なうことなく、加熱した後、タンデム圧延を行なえばよい。
[Step 5]
In step 5, based on the distance difference (xy) calculated in step 4 above, when the distance difference exceeds a predetermined value, the square steel material surface is set so that the distance difference is equal to or less than the predetermined value. Grind. When the difference in distance is not more than a predetermined value, tandem rolling may be performed after heating without performing surface grinding.
[工程6]
工程6では、上記工程5で、前記距離の差が所定値以下になっている角鋼材をタンデム圧延機で粗圧延を行なう。
[Step 6]
In step 6, the square steel material in which the difference in distance is equal to or less than a predetermined value in step 5 is rough-rolled with a tandem rolling mill.
タンデム圧延機は、圧延方向が互いに直交するスタンドを交互に並べた圧延機であり、スタンドには圧延方向が垂直方向または水平方向となるように圧延ロールが設けられている。 The tandem rolling mill is a rolling mill in which stands whose rolling directions are orthogonal to each other are alternately arranged, and the stands are provided with rolling rolls so that the rolling direction is a vertical direction or a horizontal direction.
粗圧延の条件は特に限定されず、例えば、ダイヤスクエアパススケジュールに従って圧延すればよい。即ち、圧延ロールに菱カリバーを設け、角鋼材の断面形状を、角形→横方向に偏平した菱形→縦方向に偏平した菱形→横方向に偏平した菱形と繰返し変形しつつ断面積を小さくして圧延すればよい。 The conditions for rough rolling are not particularly limited, and for example, rolling may be performed according to a diamond square pass schedule. In other words, the rolling roll is provided with a rhombus caliber, and the cross-sectional shape of the square steel material is reduced by repeatedly deforming the cross-sectional shape of the square steel material from square → rhombus flattened in the horizontal direction → rhombus flattened in the vertical direction → rhombus flattened in the horizontal direction. What is necessary is just to roll.
粗圧延した後は、続いて中間圧延と仕上げ圧延を行なえば、棒鋼や線材を製造できる。中間圧延と仕上げ圧延の条件については特に限定されず、常法に従って行なえばよい。 After rough rolling, steel bars and wire rods can be manufactured by performing intermediate rolling and finish rolling. The conditions for intermediate rolling and finish rolling are not particularly limited, and may be performed according to a conventional method.
上記工程1〜工程6を経て得られる本発明の棒鋼や線材は、タンデム圧延時に鋼返りが発生していないため、表面疵が発生しておらず、しかもこの棒鋼や線材を鍛造しても表面疵が発生することがない。 The steel bars and wires of the present invention obtained through the above steps 1 to 6 are free of surface flaws during tandem rolling, so that surface flaws do not occur, and even if this steel bar or wire is forged, the surface No wrinkles occur.
本発明で得られる棒鋼や線材の断面形状は特に限定されず、丸状であってもよいし、角状、六角状であってもよい。 The cross-sectional shape of the steel bar or wire obtained in the present invention is not particularly limited, and may be round, square, or hexagonal.
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・後記の趣旨に適合し得る範囲で適当に変更して実施することも可能であり、それらはいずれも本発明の技術的範囲に含まれる。 Hereinafter, the present invention will be described in more detail with reference to examples. However, the following examples are not intended to limit the present invention, and may be implemented with appropriate modifications within a range that can meet the purpose described above and below. These are all possible and are within the scope of the present invention.
[予備実験]
断面形状が略正方形(約155mm×約155mm)の角鋼材を製造し、該角鋼材の表面を研削して断面の2組の対辺距離の差を種々変化させた後、タンデム圧延を行なった。このとき圧延ロールに設けられたモーターに、電流変動測定装置を設け、モーターに供給される電流の変動を監視することによって鋼返りの発生の有無を調べた。次に、鋼返りが発生することなく得られた丸棒鋼(φ32.0mm)を熱間鍛造し、表面疵が発生するかどうか調べた。
[Preliminary experiment]
A square steel material having a cross-sectional shape of approximately square (about 155 mm × about 155 mm) was manufactured, and the surface of the square steel material was ground to change the difference between two pairs of opposite side distances in various ways, followed by tandem rolling. At this time, the motor provided in the rolling roll was provided with a current fluctuation measuring device, and the occurrence of steel return was examined by monitoring fluctuations in the current supplied to the motor. Next, the round bar steel (φ32.0 mm) obtained without steel return was hot forged to examine whether surface defects occurred.
その結果、タンデム圧延時に鋼返りが発生せずに、しかも得られた丸棒鋼を鍛造したときに表面疵が発生しない丸棒鋼を製造するには、タンデム圧延前における角鋼材の断面について、2組の対辺の距離の差が3.5mm以下に調整すればよいことが分かった。この3.5mmを本実施例で用いたタンデム圧延機の所定値とする。 As a result, in order to produce a round bar steel that does not generate steel return during tandem rolling and does not generate surface defects when the obtained round bar steel is forged, two sets of square steel cross sections before tandem rolling are produced. It has been found that the difference in the distance between the opposite sides may be adjusted to 3.5 mm or less. This 3.5 mm is set as a predetermined value of the tandem rolling mill used in this example.
なお、タンデム圧延機のうち、粗圧延用に設けられたスタンドについて、隣り合うスタンド間距離を測定したところ、最大距離は2.5mであった。 In addition, about the stand provided for rough rolling among tandem rolling mills, when the distance between adjacent stands was measured, the maximum distance was 2.5 m.
[比較例1]
角鋼材として、断面が153.1mm×156.7mmで、2組の対辺の距離の差が3.6mmの角鋼材を製造した(工程1)。
[Comparative Example 1]
As a square steel material, a square steel material having a cross section of 153.1 mm × 156.7 mm and a difference in distance between two pairs of opposite sides of 3.6 mm was manufactured (step 1).
得られた角鋼材について表面疵探傷を行なった(工程2)。このとき内部疵探傷も行なった。表面疵探傷は、磁紛探傷を自動で行ない、表面疵が発生している部分を目視で確認し、自動または手動でマーキングした。 The obtained square steel was subjected to surface flaw detection (Step 2). At this time, internal flaw detection was also performed. For surface flaw detection, magnetic flaw detection was automatically performed, and a portion where surface flaws occurred was visually confirmed and marked automatically or manually.
内部疵探傷は、超音波探傷を行ない、角鋼材内部に異常があるかどうか確認した。内部疵が発見されたものについてはスクラップとして廃棄処分した。 For internal flaw detection, ultrasonic flaw detection was performed to check whether there was any abnormality inside the square steel. Those found with internal dredging were discarded as scrap.
比較例1では、表面疵探傷と内部疵探傷を行なった結果、表面疵も内部疵も認められなかった。 In Comparative Example 1, as a result of surface flaw detection and internal flaw detection, neither surface flaws nor internal flaws were observed.
表面疵も内部疵も認められなかったため、そのままタンデム圧延機で粗圧延を行ない、次いで中間圧延と仕上げ圧延を行なって丸棒鋼(φ32.0mm)を製造した(工程6)。 Since neither surface flaws nor internal flaws were observed, rough rolling was performed with a tandem rolling mill as it was, and then intermediate rolling and finish rolling were performed to produce round steel bars (φ32.0 mm) (Step 6).
タンデム圧延機のうち粗圧延用圧延ロールに設けられたモーターに、電流変動測定装置を設け、モーターに供給される電流の変動を監視することによって鋼返りの発生の有無を調べた。その結果、鋼返りが発生していた。得られた丸棒鋼の表面を観察すると、線状の疵が認められた。 Of the tandem rolling mill, a motor provided on a rolling roll for rough rolling was provided with a current fluctuation measuring device, and the occurrence of steel return was examined by monitoring fluctuations in the current supplied to the motor. As a result, steel return occurred. When the surface of the obtained round steel bar was observed, linear wrinkles were observed.
[比較例2]
角鋼材として、断面が153.4mm×156.7mmで、2組の対辺の距離の差が3.3mmの角鋼材を製造した(工程1)。
[Comparative Example 2]
As a square steel material, a square steel material having a cross section of 153.4 mm × 156.7 mm and a difference in distance between two sets of opposite sides of 3.3 mm was manufactured (step 1).
得られた角鋼材について、上記比較例1と同様に、表面疵探傷を行なった(工程2)。このとき上記比較例1と同様に、内部疵探傷も行なった。内部疵探傷を行なった結果、内部疵は認められなかったが、表面疵探傷を行なった結果、角鋼材の先端から1m付近の位置における角鋼材表面に、複数個の表面疵が認められたため、認められた表面疵を全て含むように、角鋼材の幅方向に向かって全面グラインダーを行なって表面研削を行なった(工程3)。 About the obtained square steel material, surface flaw detection was performed similarly to the said comparative example 1 (process 2). At this time, as in Comparative Example 1, internal flaw detection was also performed. As a result of internal flaw detection, internal flaws were not recognized, but as a result of surface flaw detection, a plurality of surface flaws were observed on the square steel material surface at a position near 1 m from the tip of the square steel material. Surface grind was performed by grinding the entire surface in the width direction of the square steel material so as to include all the recognized surface defects (Step 3).
表面研削して表面疵を除去した後、再度、表面探傷を行なった。その結果、表面疵が完全に除去されていることを確認した。 After surface grinding to remove surface defects, surface flaw detection was performed again. As a result, it was confirmed that the surface defects were completely removed.
次に、表面疵を除去した後の角鋼材の断面について、2組の対辺の距離を測定して対辺の距離の差を算出すると3.5mmを超えていたが、この角鋼材をそのままタンデム圧延機で粗圧延を行ない、次いで中間圧延と仕上げ圧延を行なって丸棒鋼(φ32.0mm)を製造した(工程6)。粗圧延時には、鋼返りが発生していた。得られた丸棒鋼の表面には、表面疵が認められた。 Next, for the cross section of the square steel material after removing the surface flaws, the distance between the two opposite sides was measured and the difference between the opposite sides was calculated to be over 3.5 mm. Rough rolling was performed with a machine, and then intermediate rolling and finish rolling were performed to produce a round steel bar (φ32.0 mm) (step 6). During rough rolling, steel turning occurred. Surface flaws were observed on the surface of the obtained round bar steel.
[発明例]
角鋼材として、断面が152.1mm×155.8mmで、2組の対辺の距離の差が3.7mmの角鋼材を製造した(工程1)。
[Invention Example]
As a square steel material, a square steel material having a cross section of 152.1 mm × 155.8 mm and a difference in distance between two pairs of opposite sides of 3.7 mm was manufactured (step 1).
得られた角鋼材について、上記比較例1と同様に、表面疵探傷を行なった(工程2)。このとき上記比較例1と同様に、内部疵探傷も行なった。内部疵探傷を行なった結果、内部疵は認められなかったが、表面疵探傷を行なった結果、角鋼材の先端から2m付近の位置における角鋼材表面に、複数個の表面疵が認められたため、認められた表面疵を全て含むように、角鋼材の幅方向に向かって全面グラインダーを行なって表面研削を行なった(工程3)。 About the obtained square steel material, surface flaw detection was performed similarly to the said comparative example 1 (process 2). At this time, as in Comparative Example 1, internal flaw detection was also performed. As a result of internal flaw detection, internal flaws were not recognized, but as a result of surface flaw detection, a plurality of surface flaws were found on the square steel surface at a position near 2 m from the tip of the square steel material. Surface grind was performed by grinding the entire surface in the width direction of the square steel material so as to include all the recognized surface defects (Step 3).
表面研削して表面疵を除去した後、再度、表面探傷を行なった。その結果、表面疵が完全に除去されていることを確認した。 After surface grinding to remove surface defects, surface flaw detection was performed again. As a result, it was confirmed that the surface defects were completely removed.
次に、表面疵を除去した後の角鋼材の断面について、2組の対辺の距離を測定すると、152.1mmと155.7mmであり、対辺の距離の差は3.6mmであった。 Next, when the distance between two pairs of opposite sides was measured for the cross section of the square steel material after removing the surface flaws, it was 152.1 mm and 155.7 mm, and the difference in the distance between opposite sides was 3.6 mm.
そこで、対辺の距離の差が所定値以下(3.5mm以下)となるように、上記工程3で研削した面に対して垂直な面を全面グラインダーして研削した(工程5)。 Then, the surface perpendicular | vertical with respect to the surface ground at the said process 3 was grinded and grind | polished so that the difference of the distance of an opposite side may be below a predetermined value (3.5 mm or less) (process 5).
工程5で表面を研削した後、角鋼材の断面について、2組の対辺の距離を測定すると、152.1mmと155.5mmであり、対辺の距離の差は3.4mmであった。 After grinding the surface in step 5, when measuring the distance between two pairs of opposite sides of the cross section of the square steel material, they were 152.1 mm and 155.5 mm, and the difference in the distance between opposite sides was 3.4 mm.
対辺の距離の差を調整した角鋼材をタンデム圧延機で粗圧延を行ない、次いで中間圧延と仕上げ圧延を行なって丸棒鋼(φ32.0mm)を製造した(工程6)。粗圧延時には、鋼返りが発生していなかった。得られた丸棒鋼を熱間鍛造しても、表面疵は認められなかった。 The square steel with the difference in the distance between the opposite sides was subjected to rough rolling with a tandem rolling mill, and then subjected to intermediate rolling and finish rolling to produce round bar steel (φ32.0 mm) (step 6). During rough rolling, no steel return occurred. Even when the obtained round bar steel was hot forged, no surface flaws were observed.
以上の結果を下記表2にまとめて示す。 The above results are summarized in Table 2 below.
Claims (2)
粗圧延前に、前記角鋼材の断面について2組の対辺の距離を夫々測定し、それらの距離の差が所定値を超える場合には、該距離の差が所定値以下となるように角鋼材の表面を研削してからタンデム圧延することを特徴とする棒鋼または線材の製造方法。 A method of roughly manufacturing a square steel material having a substantially square cross-sectional shape by a tandem rolling machine in which stands whose rolling directions are orthogonal to each other are alternately arranged, and then continuing further rolling to produce a bar steel or a wire,
Before rough rolling, the distance between two pairs of opposite sides is measured for the cross section of the square steel material, and when the difference between the distances exceeds a predetermined value, the square steel material is set so that the difference in distance is not more than the predetermined value. A method for producing a steel bar or wire, characterized by grinding the surface of the steel and then tandem rolling.
断面形状が略正方形の角鋼材を製造する工程(工程1)、前記角鋼材の表面疵探傷を行なう工程(工程2)、前記工程2で発見された表面疵を、角鋼材表面を研削することによって除去する工程(工程3)、前記工程3の後、角鋼材の断面について、2組の対辺の距離を夫々測定し、それらの距離の差を算出する工程(工程4)、前記距離の差が所定値を超える場合には、該距離の差が所定値以下となるように角鋼材表面を研削する工程(工程5)、前記距離の差が所定値以下になっている角鋼材をタンデム圧延する工程(工程6)、を含むことを特徴とする棒鋼または線材の製造方法。 A method of roughly manufacturing a square steel material having a substantially square cross-sectional shape by a tandem rolling machine in which stands whose rolling directions are orthogonal to each other are alternately arranged, and then continuing further rolling to produce a bar steel or a wire,
A step of manufacturing a square steel material having a substantially square cross section (Step 1), a step of performing surface flaw detection on the square steel material (Step 2), and grinding the surface of the square steel material with the surface flaw found in Step 2 above. Step (step 3) to be removed by the step, after the step 3, for the cross section of the square steel material, measuring the distance between two pairs of opposite sides, respectively, calculating the difference between these distances (step 4), the difference in the distance Is greater than a predetermined value, the step of grinding the surface of the square steel material such that the difference in distance is less than or equal to the predetermined value (step 5), and the square steel material in which the difference in distance is less than or equal to the predetermined value is tandem rolled. The manufacturing method of the steel bar or wire characterized by including the process (process 6) to perform.
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