JP6358307B2 - Steel strip notching method, cold rolling method, and cold rolled steel strip manufacturing method - Google Patents
Steel strip notching method, cold rolling method, and cold rolled steel strip manufacturing method Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims description 48
- 239000010959 steel Substances 0.000 title claims description 48
- 238000000034 method Methods 0.000 title claims description 31
- 238000005097 cold rolling Methods 0.000 title claims description 22
- 239000010960 cold rolled steel Substances 0.000 title claims description 9
- 238000004519 manufacturing process Methods 0.000 title claims description 9
- 238000003698 laser cutting Methods 0.000 claims description 27
- 238000005520 cutting process Methods 0.000 claims description 13
- 239000007789 gas Substances 0.000 claims description 10
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 7
- 229910052757 nitrogen Inorganic materials 0.000 claims description 4
- 238000005304 joining Methods 0.000 claims description 2
- 230000015572 biosynthetic process Effects 0.000 claims 1
- 239000000463 material Substances 0.000 description 23
- 238000005096 rolling process Methods 0.000 description 19
- 238000010008 shearing Methods 0.000 description 19
- 238000003466 welding Methods 0.000 description 13
- 229910000976 Electrical steel Inorganic materials 0.000 description 11
- 239000000956 alloy Substances 0.000 description 9
- 238000012545 processing Methods 0.000 description 9
- 229910052710 silicon Inorganic materials 0.000 description 8
- 238000005336 cracking Methods 0.000 description 7
- 238000005482 strain hardening Methods 0.000 description 7
- 238000012360 testing method Methods 0.000 description 6
- 238000011156 evaluation Methods 0.000 description 5
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 4
- 238000009826 distribution Methods 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 238000003754 machining Methods 0.000 description 2
- 239000000155 melt Substances 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000002436 steel type Substances 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 1
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Description
本発明は、鋼帯の接合部にノッチングを施すためのノッチング方法、冷間圧延方法および冷延鋼帯の製造方法に関する。 The present invention relates to a notching method, a cold rolling method, and a method for producing a cold-rolled steel strip for notching a joint portion of a steel strip.
鋼帯の冷間圧延工程においては、生産性の向上や歩留りの向上を目的に、先行材（先行鋼帯）の後端と後行材（後行鋼帯）の先端とを接合し、連続的に冷間圧延ラインに供給することが一般的である。これにより、鋼帯の全長にわたり、張力を付与した状態で圧延することが可能になり、鋼帯の先端や後端においても、板厚や形状を高精度に制御することができる。 In the cold rolling process of steel strip, the rear end of the preceding material (leading steel strip) and the front end of the following material (following steel strip) are joined for the purpose of improving productivity and yield. In general, it is generally supplied to a cold rolling line. Thereby, it becomes possible to roll in the state which gave tension over the full length of a steel strip, and sheet thickness and shape can be controlled with high precision also in the front-end | tip and rear end of a steel strip.
冷延鋼帯の高合金化やレーザ溶接機の進歩に伴い、先行材と後行材の接合は、従来のフラッシュバット溶接等に替わって、レーザ溶接で接合されることが主流になりつつあるが、フラッシュバット溶接やレーザ溶接などの溶接手段に関わらず、先行材と後行材の接合部（溶接部）の板幅方向端部は、先行材と後行材の鋼帯幅の差や位置ずれなどのために、不可避的に幅段差部が形成される。そして、このままの状態で圧延すると、前記幅段差部に応力集中が生じ、溶接部で破断に至る可能性がある。溶接部での破断（溶接部破断）が生じると、冷間圧延ラインを停止せざるを得ないため、生産性を著しく低下させるとともに、ワークロールを交換する必要が生じるため、生産コストの上昇を招く。 With the advancement of high-alloy cold-rolled steel strips and laser welding machines, the joining of leading and trailing materials is becoming the mainstream instead of conventional flash butt welding, etc. However, regardless of the welding means such as flash butt welding or laser welding, the plate width direction end of the joining part (welding part) of the preceding material and the succeeding material is the difference in the steel strip width between the preceding material and the following material. A width step portion is inevitably formed due to misalignment or the like. And if it rolls in this state, stress concentration will arise in the said width | variety level | step-difference part, and it may lead to a fracture | rupture in a welding part. When breakage occurs at the welded part (welded part breakage), the cold rolling line has to be stopped, so the productivity is significantly reduced and the work roll needs to be replaced. Invite.
特に、近年は、部材の軽量化や特性向上を目的に、冷延鋼帯の薄ゲージ化に対する要求はますます強くなっている。それに伴い、冷間圧延に要求される圧下率は高くなりつつあり、溶接部の破断率が高くなっているのが現状である。 In particular, in recent years, the demand for thinner gauges of cold-rolled steel strips has been increasing for the purpose of reducing the weight of members and improving their properties. Along with this, the reduction ratio required for cold rolling is increasing, and the current state is that the fracture ratio of the welded portion is increased.
そこで、溶接部での破断を防止するために、溶接部の板幅方向端部にノッチ（切り欠き）を形成するノッチングを行ってから圧延することが行われている。また、このノッチングには、鋼帯の板幅端部は突合せ精度なども悪く、溶接が不十分になり、強度が低くなり易いため、強度の低い部分（概ね、板幅端３０ｍｍ程度）を切り落とす狙いもある。 Therefore, in order to prevent breakage at the welded portion, rolling is performed after performing notching for forming a notch (notch) at the end portion in the plate width direction of the welded portion. In addition, the notch notch is not good at the end of the steel strip because of its poor butting accuracy, welding becomes insufficient, and the strength tends to be low. Therefore, the low-strength portion (generally about 30 mm at the width of the plate) is cut off. There is also an aim.
ノッチングの方法としては、例えば、特許文献１に開示されているように、角部を有しない半円形状に、機械的にせん断加工するのが一般的である。ただし、この半円形状のノッチは、外縁の曲率が一律であり、接合部において鋼帯の幅が最も小さくなるため、接合部において最大の応力が発生することになる。 As a notching method, for example, as disclosed in Patent Document 1, it is common to mechanically shear into a semicircular shape having no corners. However, this semicircular notch has a uniform curvature at the outer edge, and the width of the steel strip is the smallest at the joint, so that the maximum stress is generated at the joint.
これに対し、特許文献１の問題点を解消するために、特許文献２には、最大応力発生点が、溶接部以外に位置するように、略等脚台形状にノッチングする方法が開示されている。また、特許文献３には、ノッチング時間を短くするための方法としてレーザ切断を用いる方法が開示されている。 On the other hand, in order to solve the problem of Patent Document 1, Patent Document 2 discloses a method of notching in a substantially isosceles trapezoidal shape so that the maximum stress generation point is located other than the welded portion. Yes. Patent Document 3 discloses a method using laser cutting as a method for shortening the notching time.
しかしながら、上記のようなノッチング方法では、特に、ＳｉやＭｎの含有量が多い珪
素鋼板や高張力鋼板などの脆性材料・高合金材料の冷間圧延においては、十分な効果を発揮できず、冷間圧延における接合部破断（溶接部破断）を十分に防止できていないのが現状である。
However, the notching method as described above cannot exert a sufficient effect particularly in cold rolling of brittle materials and high alloy materials such as silicon steel plates and high-tensile steel plates having a high Si and Mn content. The present situation is that the joint fracture (welded fracture) in the hot rolling cannot be sufficiently prevented.
本発明は、上記のような事情に鑑みてなされたものであり、ＳｉやＭｎの含有量が多い珪素鋼板や高張力鋼板などの脆性材料・高合金材料の場合でも、接合部破断（溶接部破断）を生じることなく冷間圧延することを可能にする、鋼帯のノッチング方法、冷間圧延方法および冷延鋼帯の製造方法を提供することを目的としている。 The present invention has been made in view of the circumstances as described above. Even in the case of a brittle material / high alloy material such as a silicon steel plate or a high-tensile steel plate having a high Si or Mn content, It is an object of the present invention to provide a steel strip notching method, a cold rolling method, and a cold-rolled steel strip manufacturing method that enable cold rolling without causing (break).
本発明者らは、上記目的を達成するため鋭意検討した結果、詳細は後述するが、従来のように、機械的にせん断加工で溶接部にノッチングを行った場合、それによって溶接部の板幅方向端部が加工硬化し、これが溶接部破断の原因になることに気が付いた。そして、そのような溶接部破断を防止するために、加工硬化を生じさせないノッチング手段としてレーザ切断機を用いることを着想した。ただし、レーザ切断によりノッチングを行ったとき、ドロスと称される溶融物が発生することがあり、このドロスが圧延ライン内の通板ロールやワークロールに接触した際に落下し、欠陥の原因となり得る。そこで、本発明者らは、ＳｉやＭｎの含有量が多い珪素鋼板や高張力鋼板などを対象としても、ドロスの発生を小さくする切断条件を見出した。 As a result of diligent investigations to achieve the above object, the present inventors have described the details later, but when the notched portion is mechanically sheared by conventional shearing as in the prior art, the plate width of the welded portion is thereby increased. It was noticed that the end of the direction was work-hardened, which caused the weld to break. And in order to prevent such a welded part fracture | rupture, it came up with using a laser cutting machine as a notching means which does not produce work hardening. However, when notching is performed by laser cutting, a melt called dross may be generated, and when this dross comes into contact with a sheet roll or work roll in the rolling line, it will cause a defect. obtain. Accordingly, the present inventors have found a cutting condition for reducing the generation of dross even for silicon steel plates, high-tensile steel plates and the like having a high Si and Mn content.
本発明は、上記の着想に基づいてなされたものであり、以下の特徴を有している。 The present invention has been made based on the above idea and has the following features.
［１］先行鋼帯の後端と後行鋼帯の先端とを接合した接合部の板幅方向端部にノッチを形成するノッチング方法であって、レーザ切断機によって切断を行い、そのレーザ出力が１ｍｓあたり０．５ｋＷ以上となるパルス切断かつ、使用するガスを圧力１．０ＭＰａ以上の窒素とすることを特徴とする鋼帯のノッチング方法。 [1] A notching method for forming a notch at the end in the plate width direction of the joint where the rear end of the preceding steel strip and the front end of the subsequent steel strip are joined, and the laser output is cut by a laser cutter. A method of notching a steel strip, characterized in that the gas used is pulse cutting with a pressure of 1.0 MPa or more, and pulse cutting with a pressure of 0.5 kW or more per ms.
［２］前記［１］に記載のノッチング方法を用いてノッチを形成して冷間圧延を行うことを特徴とする冷間圧延方法。 [2] A cold rolling method, wherein notching is formed using the notching method according to [1], and cold rolling is performed.
［３］前記［２］に記載の冷間圧延方法を用いて冷延鋼帯を製造することを特徴とする冷延鋼帯の製造方法。 [3] A method for producing a cold-rolled steel strip, comprising producing a cold-rolled steel strip using the cold rolling method according to [2].
本発明によれば、ＳｉやＭｎの含有量が多い珪素鋼板や高張力鋼板などの脆性材料・高合金材料の場合でも、接合部破断（溶接部破断）を生じることなく冷間圧延することが可能になる。 According to the present invention, even in the case of a brittle material or a high alloy material such as a silicon steel plate or a high-tensile steel plate having a high Si or Mn content, cold rolling can be performed without causing a joint fracture (weld fracture). It becomes possible.
まず、前述したように、本発明者らが、従来のようにせん断加工で溶接部にノッチングを行った場合、それによって溶接部の板幅方向端部が加工硬化し、これが溶接部破断の原因になることに気が付き、そのような溶接部破断を防止するために、溶接部の板幅方向端部が加工硬化しないノッチング手段としてレーザ切断機を用いることを着想したことについて、詳しく述べる。 First, as described above, when the present inventors have notched the welded part by shearing as in the past, this causes work hardening in the plate width direction end of the welded part, which causes the welded part to break. In order to prevent such a fracture of the welded portion, the idea of using a laser cutting machine as a notching means in which the end portion in the plate width direction of the welded portion is not work hardened will be described in detail.
すなわち、本発明者らは、溶接部で破断に至り易い原因を調査するため、以下に述べる実験室規模の圧延実験を行った。 That is, the present inventors conducted a laboratory-scale rolling experiment described below in order to investigate the cause of the tendency to break at the weld.
供試材として、３．３質量％のＳｉを含有する、板厚２ｍｍの珪素鋼板を用いて、図１に示すように、先行鋼帯１の後端と後行鋼帯２の先端とをレーザ溶接機を用いて接合した材料を用意し、溶接部３の一部を含むようにして、溶接方向に垂直な方向が長辺になる矩形の供試材（圧延評価用供試材）４をせん断加工により切り出し採取した。 Using a silicon steel plate having a thickness of 2 mm containing 3.3% by mass of Si as a test material, as shown in FIG. 1, the rear end of the preceding steel strip 1 and the front end of the subsequent steel strip 2 are Prepare a material joined using a laser welding machine, shear a rectangular specimen (rolling evaluation specimen) 4 having a long side in a direction perpendicular to the welding direction so as to include a part of the weld 3. It was cut out and collected by processing.
この様にして作製した供試材４を、張力を付与することなく、ワークロール径５００ｍｍの圧延機を用い、３パスで総圧下率９０％の冷間圧延を行った。 The specimen 4 thus produced was cold-rolled with a total rolling reduction of 90% in 3 passes using a rolling mill having a work roll diameter of 500 mm without applying tension.
図２に、得られた冷間圧延後の鋼板の外観を撮影した写真を示す。張力を付与しない場合でも、溶接部（溶接金属部）３でエッジ割れが発生していることが分かる。実生産のように、張力を付与して圧延するタンデム圧延では、このエッジ割れが溶接部破断の起点になると推定される。 In FIG. 2, the photograph which image | photographed the external appearance of the obtained steel plate after the cold rolling is shown. Even when no tension is applied, it can be seen that edge cracks occur in the welded portion (welded metal portion) 3. In tandem rolling in which tension is applied and rolled as in actual production, it is estimated that this edge crack is the starting point of the weld fracture.
そして、溶接部３をせん断加工した段階、すなわち、冷間圧延する前の段階において、板幅方向端部を板幅方向に切断した断面（エッジ断面）の組織観察と硬さ試験を行った。図３に結果を示す。図３（ａ）はエッジ断面の組織であり、図３（ｂ）はエッジ断面の硬度分布である。このように、溶接部の板幅方向端部がせん断加工により、加工硬化しており、これが、エッジ割れの原因になると推定された。 And in the stage which carried out the shearing process of the weld part 3, ie, the stage before cold rolling, the structure | tissue observation and the hardness test of the cross section (edge cross section) which cut | disconnected the edge part in the plate width direction were performed. The results are shown in FIG. FIG. 3A shows the structure of the edge cross section, and FIG. 3B shows the hardness distribution of the edge cross section. Thus, the plate width direction end portion of the welded portion was work-hardened by shearing, and this was estimated to cause edge cracking.
そこで、本発明者らは、機械的エネルギー（力学的エネルギー）による加工手法であるせん断加工に替えて、光学的エネルギーによる加工手法であるレーザ切断によって加工することを試みた。 Therefore, the present inventors tried to process by laser cutting, which is a processing technique using optical energy, instead of shearing, which is a processing technique using mechanical energy (mechanical energy).
すなわち、上述と同様の圧延実験において、せん断加工に代わり、レーザ切断によって、図１に示した供試材４を切り出し採取した。その際、レーザ切断機は、発振器にＩＰＧ製ＹＬＳ−５０００、加工ヘッドにプレシテック製ＹＫ２５を用い、ガス種、出力、切断速度、ガス圧等の各条件を表１に示す条件に変更して切断した。なお、出力欄が上下２段となっているものは上段と下段の繰り返しであり、例えば上段１．２（４ｍｓ）下段１．０（１ｍｓ）と記載された条件は１．２ｋＷで４ｍｓ照射→１．０ｋＷで１ｍｓ照射→１．２ｋＷで４ｍｓ照射・・・の繰り返しを意味する。また、表１には、それぞれの条件における切断面の荒れおよびドロスと称される溶融物の高さの評価結果も合わせて示している。なお、それらの指標の評価基準は表２に示す通りとする。 That is, in the same rolling experiment as described above, the specimen 4 shown in FIG. 1 was cut out and collected by laser cutting instead of shearing. At that time, the laser cutting machine uses IPG YLS-5000 for the oscillator and Precitec YK25 for the processing head, and changes the conditions such as gas type, output, cutting speed, gas pressure, etc. to the conditions shown in Table 1 for cutting. did. Note that the output column in the upper and lower stages is the repetition of the upper stage and the lower stage. For example, the condition described as the upper stage 1.2 (4 ms) and the lower stage 1.0 (1 ms) is 1.2 kW for 4 ms irradiation → It means 1 ms irradiation at 1.0 kW → 4 ms irradiation at 1.2 kW ... Table 1 also shows the evaluation results of the roughness of the cut surface and the height of the melt called dross under each condition. The evaluation criteria for these indices are as shown in Table 2.
使用するガスを酸素とした場合、酸化反応熱を利用することにより低出力での切断が可能となる。しかし、送り速度が遅い条件および出力が高い条件では、レーザを照射していない部分で溶融が進展するセルフバーニング現象が生じる。また、今回供試材としたような高合金材料においては、酸化物が生成しやすく、ドロス発生量が多くなるため、酸素切断ではドロスフリーとすることが困難である。一方の窒素切断は酸化反応熱がない分高出力が必要となるが、酸化物が生成しないため、ガス圧を高めることでドロスフリーな切断面が得られることが判明した。 When oxygen is used as the gas to be used, cutting with low output becomes possible by utilizing oxidation reaction heat. However, under conditions where the feed speed is slow and the output is high, a self-burning phenomenon occurs in which melting progresses in a portion where the laser is not irradiated. Moreover, in a high alloy material such as that used as a test material this time, oxides are easily generated and the amount of dross generated increases, so that it is difficult to make dross free by oxygen cutting. On the other hand, nitrogen cutting requires high output because there is no heat of oxidation reaction, but since no oxide is formed, it has been found that a dross-free cut surface can be obtained by increasing the gas pressure.
本発明者らが切断条件を種々に変更してノッチングを行い、鋭意検討したところ、適正な条件としては、ガス種を窒素とし、その圧力を１．０ＭＰａ以上、レーザ出力を１ｍｓあたり０．５ｋＷ以上のパルス切断とすることで、図４（ａ）に示すような、ドロス高さが０．２ｍｍ以下である良好な切断面が得られた。ここでレーザ出力を変化させる場合には常にレーザ出力を１ｍｓあたり０．５ｋＷ以上となるようにする。ドロスが０．２ｍｍを超えて発生すると、タンデム圧延機内の通板ロールや圧延ロールに接触した際にドロスが落下し、欠陥の原因となるため、ドロスは０．２ｍｍ以下にする必要がある。本条件では、ほとんどドロスを発生させることなく切断することができたが、例えばガス圧を低下させると、図４（ｂ）に示すようにドロス量が増え、最終的には切断することができなくなる。 The inventors have made notching by changing the cutting conditions in various ways, and intensively studied. As appropriate conditions, the gas type is nitrogen, the pressure is 1.0 MPa or more, and the laser output is 0.5 kW per ms. By performing the above pulse cutting, a good cut surface having a dross height of 0.2 mm or less as shown in FIG. 4A was obtained. Here, when changing the laser output, the laser output is always set to 0.5 kW or more per 1 ms. If the dross exceeds 0.2 mm, the dross falls when it comes into contact with the sheet-rolling roll or the rolling roll in the tandem rolling mill and causes a defect. Therefore, the dross needs to be 0.2 mm or less. Under these conditions, cutting was possible with almost no dross. However, for example, when the gas pressure is lowered, the amount of dross increases as shown in FIG. Disappear.
図５に、切断面が良好となる条件でレーザ切断を行ったときに得られた冷間圧延後の鋼板の外観（上記の図２に対応）を示し、図６に、エッジ断面の組織観察と硬さ試験の結果（上記の図３に対応）を示す。レーザ切断では、エッジ割れは発生せずに平滑なエッジ形状であるとともに、溶接部の板幅方向端部で加工硬化していないことが分かる。 FIG. 5 shows the appearance (corresponding to FIG. 2 above) of the steel sheet after cold rolling obtained when laser cutting is performed under the condition that the cut surface is good, and FIG. 6 shows the structure observation of the edge cross section. And the result of the hardness test (corresponding to FIG. 3 above). In laser cutting, it can be seen that edge cracking does not occur and the edge shape is smooth and is not work hardened at the end in the plate width direction of the weld.
このように、溶接部におけるエッジ割れの原因は、せん断加工による板幅方向端部の加工時のエッジの加工硬化であり、レーザ切断など、加工硬化しない加工手法では、エッジ割れが発生しないことが示された。ここで、「加工硬化が生じない」とは、例えば、加工前の硬さに比べて、加工後の硬さの上昇量が、ビッカース硬さＨｖで５０未満であることを意味している。 As described above, the cause of edge cracking in the welded portion is work hardening of the edge at the time of processing in the end portion in the plate width direction by shearing, and edge cracking may not occur in processing methods that do not work hardening such as laser cutting. Indicated. Here, “work hardening does not occur” means, for example, that the amount of increase in hardness after processing is less than 50 in terms of Vickers hardness Hv compared to the hardness before processing.
次に、本発明の実施形態について述べる。 Next, an embodiment of the present invention will be described.
［実施形態１］
図７は、本発明の実施形態１を示す図である。この実施形態１においては、レーザ切断機を備えたノッチング設備が設置されており、図７に示すように、先行鋼帯１と後行鋼帯２との溶接部３の板幅方向端部を含めた所定範囲に対して、レーザ切断１１によって、円弧状のノッチ１２を形成している。
[Embodiment 1]
FIG. 7 is a diagram showing Embodiment 1 of the present invention. In this Embodiment 1, the notching equipment provided with the laser cutting machine is installed, and as shown in FIG. 7, the plate width direction edge part of the welding part 3 of the preceding steel strip 1 and the succeeding steel strip 2 is shown. An arc-shaped notch 12 is formed by laser cutting 11 over a predetermined range.
これによって、この実施形態１では、溶接部の板幅方向端部に加工硬化が生じることなくノッチ１２を形成することができ、ＳｉやＭｎの含有量が多い珪素鋼板や高張力鋼板などの脆性材料・高合金材料の場合でも、溶接部破断を発生することなく冷間圧延することが可能になる。 Thus, in the first embodiment, the notch 12 can be formed without causing work hardening at the end portion in the plate width direction of the welded portion, and brittleness such as a silicon steel plate or a high-tensile steel plate having a high content of Si or Mn. Even in the case of a material or a high alloy material, it is possible to perform cold rolling without causing a weld fracture.
［実施形態２］
上記の実施形態１のように、溶接部３の板幅方向端部を含めた所定範囲に対して、レーザ切断１１によってノッチ１２を形成すると、加工時間が長くなる場合などは、高速加工が可能であるせん断加工によるノッチングを組み合わせるようにしても良い。
[Embodiment 2]
If the notch 12 is formed by laser cutting 11 for a predetermined range including the end in the plate width direction of the welded part 3 as in the first embodiment, high speed machining is possible when the machining time is long. You may make it combine notching by the shearing process which is.
そのようなノッチング方法を、本発明の実施形態２として図８に示している。すなわち、この実施形態２においては、レーザ切断機に加えて、併用するせん断加工機を備えたノッチング設備が設置されており、図８に示すように、先行鋼帯１と後行鋼帯２の溶接部３の板幅方向端部を含めた所定範囲に対して、せん断加工１３により１段目のノッチングを施して円弧状のノッチを形成した後、溶接部３を含めた溶接部３近傍のみ、加工硬化した部分をレーザ切断１４による２段目のノッチングで除去し、最終的にノッチ１５を形成するようにしている。 Such a notching method is shown in FIG. 8 as Embodiment 2 of the present invention. That is, in this Embodiment 2, in addition to the laser cutting machine, notching equipment provided with a shearing machine to be used in combination is installed, and as shown in FIG. 8, the preceding steel strip 1 and the subsequent steel strip 2 After a first step notching is performed by shearing 13 on a predetermined range including the end in the plate width direction of the welded portion 3 to form an arc-shaped notch, only the vicinity of the welded portion 3 including the welded portion 3 is formed. The work-hardened portion is removed by second-stage notching by laser cutting 14, and finally the notch 15 is formed.
これによって、この実施形態２では、溶接部の板幅方向端部において、加工硬化した個所が無いノッチ１５を短い加工時間で形成することができ、ＳｉやＭｎの含有量が多い珪素鋼板や高張力鋼板などの脆性材料・高合金材料の場合でも、溶接部破断を発生することなく冷間圧延することが可能になる。 Thus, in the second embodiment, the notch 15 having no work-hardened portion can be formed in a short processing time at the end portion in the plate width direction of the welded portion, and the silicon steel plate or the high content of Si or Mn is high. Even in the case of a brittle material or a high alloy material such as a tensile steel plate, it is possible to perform cold rolling without causing a weld fracture.
また、本発明においては、ノッチング形状を特に規定するものではない。特許文献１に記載のように半円状にノッチングしても良いし、特許文献２に記載のように略等脚台形状にノッチングしても良い。また、上記以外の形状でも何ら問題ない。 In the present invention, the notching shape is not particularly specified. As described in Patent Document 1, it may be notched in a semicircular shape, or as described in Patent Document 2, it may be notched in a substantially isosceles trapezoidal shape. Further, there is no problem with shapes other than those described above.
さらに付け加えると、通常の低炭素鋼であれば、せん断加工の場合でもエッジ割れは発生しないが、ＳｉやＭｎの含有量が多い珪素鋼板や高張力鋼板などの脆性材料・高合金材料では溶接部の加工性が乏しいため、せん断加工により加工硬化するとエッジ割れが発生し易い。すなわち、通常の低炭素鋼など、せん断加工でもエッジ割れが発生せず、溶接部破断がほとんど発生しない鋼種には、必ずしも本発明を適用する必要はなく、せん断加工では溶接部で破断する脆性材料や高合金材料などの鋼種に適用すべきである。ただし、冷間タンデム圧延機では、珪素鋼板や高張力鋼板の専用ミルである場合もあるが、そうではなく、低炭素鋼なども合わせて圧延する兼用ミルの場合もある。その場合、低炭素鋼もレーザ切断にてノッチングしても何ら問題はない。また、せん断加工機とレーザ切断機の両方を併設し、鋼種により使い分けても良い。 In addition, edge cracking does not occur even in the case of shearing with ordinary low-carbon steel, but in brittle materials and high-alloy materials such as silicon steel sheets and high-tensile steel sheets with high Si and Mn contents, Therefore, edge cracking is likely to occur when work hardening is performed by shearing. In other words, it is not always necessary to apply the present invention to a steel type such as ordinary low carbon steel that does not cause edge cracking even in shearing and hardly breaks in the welded part, and the brittle material that breaks in the welded part in shearing. And should be applied to steel grades such as high alloy materials. However, in a cold tandem rolling mill, it may be a dedicated mill for silicon steel plates or high-tensile steel plates, but it may also be a dual-purpose mill for rolling together with low carbon steel. In that case, there is no problem even if the low carbon steel is notched by laser cutting. In addition, both a shearing machine and a laser cutting machine may be provided and used depending on the steel type.
ちなみに、ＳｉやＭｎの含有量が多い珪素鋼板とは、例えば、Ｓｉ：１．０〜６．５質量％、Ｍｎ：０．２〜１．０質量％を含有した鋼板であり、ＳｉやＭｎの含有量が多い高張力鋼板とは、例えば、Ｓｉ：１．０〜２．０質量％、Ｍｎ：１．５〜２０．０質量％を含有し、引張強度が５９０〜１４７０ＭＰａの鋼板である。また、これらの鋼板は、例えば板厚が０．５ｍｍ〜３．０ｍｍの鋼板である。 Incidentally, a silicon steel plate having a large content of Si or Mn is, for example, a steel plate containing Si: 1.0 to 6.5% by mass and Mn: 0.2 to 1.0% by mass. The high-strength steel sheet with a large content of, for example, is a steel sheet containing Si: 1.0 to 2.0 mass%, Mn: 1.5 to 20.0 mass%, and having a tensile strength of 590 to 1470 MPa. . Moreover, these steel plates are steel plates with a plate thickness of 0.5 mm to 3.0 mm, for example.
本発明の実施例として、５スタンドの冷間タンデム圧延機を備えた冷間圧延設備によって珪素鋼板を製造して評価した。 As an example of the present invention, a silicon steel sheet was manufactured and evaluated by a cold rolling facility equipped with a 5-stand cold tandem rolling mill.
その際に、従来例として、先行鋼帯と後行鋼帯との溶接部をせん断加工により半円状にノッチングした。 At that time, as a conventional example, the welded portion of the preceding steel strip and the succeeding steel strip was notched in a semicircular shape by shearing.
これに対して、本発明例１として、上記の本発明の実施形態１に基づいてノッチングを行った。すなわち、先行鋼帯と後行鋼帯との溶接部をレーザ切断により半円状にノッチングした。 On the other hand, as Example 1 of the present invention, notching was performed based on Embodiment 1 of the present invention described above. That is, the welded portion between the preceding steel strip and the subsequent steel strip was notched in a semicircular shape by laser cutting.
また、本発明例２として、上記の本発明の実施形態２に基づいてノッチングを行った。すなわち、せん断加工により半円状に１段目のノッチングを行った後、溶接部近傍のみレーザ切断による２段目のノッチングを行った。 In addition, as Inventive Example 2, notching was performed based on Embodiment 2 of the present invention described above. That is, after notching the first step in a semicircular shape by shearing, the second step notching was performed by laser cutting only in the vicinity of the weld.
ここで、本発明例１および本発明例２のレーザ切断によるノッチングでは、ガス種：窒素、出力：１．０ｋＷ（４ｍｓ）と０．８ｋＷ（１ｍｓ）のパルスの繰り返し照射、切断速度：３．０ｍ／ｍｉｎ、ガス圧：１．５ＭＰａで行った。 Here, in notching by laser cutting in Invention Example 1 and Invention Example 2, gas type: nitrogen, output: repeated irradiation of pulses of 1.0 kW (4 ms) and 0.8 kW (1 ms), cutting speed: 3. The measurement was performed at 0 m / min and gas pressure: 1.5 MPa.
いずれの例においても、Ｓｉ含有量が３．１質量％以上３．５質量％未満、板厚１．８ｍｍ以上２．４ｍｍ以下の鋼帯を１００コイル用意し、上記の５スタンドの冷間タンデム圧延機で冷間圧延を行い、板厚０．３ｍｍ以上０．５ｍｍ以下に仕上げた。この際、溶接部での破断発生率を比較した。その結果を図９に示す。 In any example, 100 coils of a steel strip having a Si content of 3.1% by mass to less than 3.5% by mass and a plate thickness of 1.8 mm or more and 2.4 mm or less are prepared. It cold-rolled with the rolling mill and finished to plate thickness 0.3mm or more and 0.5mm or less. At this time, the fracture occurrence rates at the welds were compared. The result is shown in FIG.
図９に示すように、従来例では、溶接部破断の発生率が７％であるのに対し、本発明例１、２では、溶接部破断を１％にまで低下することができた。 As shown in FIG. 9, in the conventional example, the occurrence rate of the weld fracture was 7%, while in Examples 1 and 2 of the present invention, the weld fracture was reduced to 1%.
これによって、本発明の有効性が確認された。すなわち、本発明を適用し、先行鋼帯と後行鋼帯との溶接部をノッチングする際、レーザ切断などの加工手法を適用し、溶接部を加工硬化させることなくノッチングすることにより、溶接部破断を防止することが可能となり、生産性の向上、歩留りの向上を達成することができる。 This confirmed the effectiveness of the present invention. That is, when applying the present invention and notching the welded portion of the preceding steel strip and the succeeding steel strip, a welding technique is applied by applying a processing technique such as laser cutting and not hardening the welded portion. Breaking can be prevented, and productivity and yield can be improved.
１ 先行鋼帯
２ 後行鋼帯
３ 溶接部
４ 圧延評価用供試材
１１ レーザ切断
１２ ノッチ
１３ せん断加工
１４ レーザ切断
１５ ノッチ
DESCRIPTION OF SYMBOLS 1 Leading steel strip 2 Subsequent steel strip 3 Welded part 4 Test material for rolling evaluation 11 Laser cutting 12 Notch 13 Shearing 14 Laser cutting 15 Notch
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