JP2020196044A - Butt welding method for steel plate - Google Patents
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本発明は、板厚変動を考慮した鋼板の突合わせ溶接方法に関するものである。 The present invention relates to a butt welding method for steel sheets in consideration of fluctuations in sheet thickness.
鋼帯の生産性向上を目的に、冷間圧延工程では、連続圧延ライン上で先行する被圧延材の後端と、それに後行する被圧延材の先端との接合を行う。連続圧延ラインに適用される溶接方法は、一般的にはフラッシュバット溶接（Ｆｌａｓｈ ｂｕｔｔ ｗｅｌｄｉｎｇ）とレーザー溶接（Ｌａｓｅｒ Ｂｅａｍ ｗｅｌｄｉｎｇ）がある。
レーザー溶接は、エネルギー密度が高く入熱量が少ないため、フラッシュバット溶接に比べて優れた品質特性が得られる。しかし、高炭素鋼などの溶接では、溶接後の急冷により、溶接部に硬化した低温変態組織（マルテンサイト、ベイナイトが含まれた組織）が発生し、溶接部に亀裂が発生し、溶接部の破断トラブルの原因となってしまう。この溶接部の硬化に対しては、溶接後に再加熱する後加熱処理を行うことで、硬化した溶接部を焼き戻し、軟化させ溶接部の破断トラブル発生を防止している。
後加熱処理をする後加熱処理装置として、高効率で後加熱するためにレーザー溶接装置と一体となった装置が開発されており、後加熱処理は、一般的には高周波誘導コイルを使用した誘導加熱を行う方法が知られている。
In the cold rolling process, the trailing end of the material to be rolled that precedes it on the continuous rolling line and the tip of the material to be rolled that follows it are joined for the purpose of improving the productivity of the steel strip. Welding methods applied to continuous rolling lines generally include flash butt welding and laser beam welding.
Since laser welding has a high energy density and a small amount of heat input, excellent quality characteristics can be obtained as compared with flash butt welding. However, in welding of high carbon steel, etc., quenching after welding causes a hardened low-temperature transformation structure (structure containing martensite and bainite) in the weld, causing cracks in the weld and causing cracks in the weld. It causes breakage trouble. With respect to the hardening of the welded portion, the cured welded portion is tempered and softened by performing a heat treatment after reheating after welding to prevent the occurrence of breakage trouble of the welded portion.
As a post-heat treatment device for post-heat treatment, a device integrated with a laser welding device has been developed for high-efficiency post-heating, and post-heat treatment is generally guided using a high-frequency induction coil. A method of heating is known.
特許文献１には、高炭素鋼板あるいは鋼帯の突合せ溶接において、レーザー溶接を適用し、かつ溶接完了後１分以内に４００℃以上、Ａｃｌ点以下の温度範囲で後加熱処理を行うことを特徴とする高炭素鋼板あるいは鋼帯の溶接方法が開示されている。 Patent Document 1 states that laser welding is applied to butt welding of high carbon steel sheets or steel strips, and post-heat treatment is performed within 1 minute after the completion of welding in a temperature range of 400 ° C. or higher and Acl point or lower. A method for welding a characteristic high carbon steel plate or steel strip is disclosed.
特許文献２には、圧延材を連続製造工程のためにレーザー溶接する方法において、低温変態組織が発生する圧延材を相互に接触させる段階と、圧延材の接触部分に対してレーザー溶接して接触部を形成する段階と、圧延材の溶接部に対して加圧機で強制圧下する段階を含む連続製造工程のためのレーザー溶接方法が開示されている。 Patent Document 2 describes in a method of laser welding a rolled material for a continuous manufacturing process, a step of bringing the rolled materials in which a low temperature transformation structure is generated into mutual contact and a step of laser welding and contacting a contact portion of the rolled material. A laser welding method for a continuous manufacturing process including a step of forming a portion and a step of forcibly reducing the welded portion of the rolled material with a pressurizer is disclosed.
特許文献１の後加熱処理においては、高周波、火炎、高温ガスなどにより、後加熱処理の温度範囲を限定することにより、高炭素鋼の溶接を短時間かつ簡便に行うことができる。同様に、特許文献２の後加熱処理においても後加熱処理の温度範囲が開示されている。しかしながら、これら従来技術では、板厚変動を考慮した最適な後加熱処理条件を適用して鋼板を溶接する発明ではない。 In the post-heat treatment of Patent Document 1, welding of high carbon steel can be performed in a short time and easily by limiting the temperature range of the post-heat treatment with a high frequency wave, a flame, a high temperature gas, or the like. Similarly, in the post-heat treatment of Patent Document 2, the temperature range of the post-heat treatment is disclosed. However, these conventional techniques are not inventions in which a steel sheet is welded by applying optimum post-heat treatment conditions in consideration of plate thickness variation.
本発明は上記課題に鑑みてなされたものであって、鋼板を圧延した際に溶接部の破断トラブル発生を回避でき、コイルの生産性を向上させることを目標とする。 The present invention has been made in view of the above problems, and an object of the present invention is to avoid the occurrence of breakage trouble in a welded portion when a steel sheet is rolled, and to improve the productivity of a coil.
図１は、熱間圧延後の鋼帯板厚チャートを表す図である。図１に記載のＴＯＰ、ＥＮＤは、先行する被圧延材の後端とそれに後行する被圧延材の先端を溶接した箇所を示す。これらの場所では、板厚がその他の場所よりも大きく変動していることがわかる。この箇所で溶接を行った場合、予め設定された設定板厚よりも測定された板厚が大きい場合は後加熱不足、予め設定された設定板厚よりも測定された板厚が小さい場合は後加熱過多となり、最適な熱量の範囲（後加熱の合格範囲）を外れてしまうことがある。これに気付かずに圧延した場合、安定的に最適な条件で後加熱を行うことができず、鋼板を圧延した際に溶接部の破断トラブル発生を回避できずコイルの生産性が低下する。
このように、板厚を考慮して後加熱処理時にその電流値を溶接部ごとに変更して、最適な後加熱処理条件を適用して鋼板を溶接する発明する技術はまだ確立されていなかった。
FIG. 1 is a diagram showing a steel strip thickness chart after hot rolling. TOP and END shown in FIG. 1 indicate a portion where the rear end of the preceding material to be rolled and the tip of the material to be rolled following it are welded. It can be seen that the plate thickness fluctuates more in these places than in other places. When welding is performed at this point, post-heating is insufficient if the measured plate thickness is larger than the preset plate thickness, and later if the measured plate thickness is smaller than the preset plate thickness. Overheating may occur and the amount of heat may be out of the optimum range (passing range for post-heating). If the coil is rolled without noticing this, post-heating cannot be stably performed under the optimum conditions, and when the steel sheet is rolled, the trouble of breaking the welded portion cannot be avoided and the productivity of the coil is lowered.
As described above, a technique for inventing a steel sheet to be welded by changing the current value for each welded portion in consideration of the plate thickness and applying the optimum post-heat treatment conditions has not yet been established. ..
本発明は上記知見に基づいたものであり、以下［１］〜［８］を提供する。
［１］ 先行鋼板と後行鋼板とを突合せ溶接する方法であって、前記先行鋼板と前記後行鋼板のそれぞれの溶接部となる部分の板厚を測定する板厚測定工程と、前記先行鋼板と前記後行鋼板とを突合せ溶接する溶接工程と、前記板厚測定工程で測定された前記板厚に基づいて前記突合せ溶接後に前記溶接部を加熱するための後加熱電流値を決定する後加熱決定工程と、前記後加熱決定工程で決定した前記後加熱電流値に基づいて前記それぞれの溶接部を加熱する工程と、を含む、鋼板の突合せ溶接方法。
［２］ 前記後加熱決定工程において、前記板厚測定工程で測定された前記先行鋼板の溶接部となる部分の板厚と、前記後行鋼板の溶接部となる部分の板厚との平均測定板厚に基づいて前記後加熱電流値を決定する、［１］に記載の鋼板の突合せ溶接方法。
［３］ 前記後加熱決定工程において、予め設定された後加熱電流値と、前記先行鋼板と前記後行鋼板の平均設定板厚と、平均測定板厚とに基づいて下記式（１）を満足するように後加熱電流値を決定する、［１］または［２］に記載の鋼板の突合せ溶接方法。
The present invention is based on the above findings, and the following [1] to [8] are provided.
[1] A method of butt-welding a leading steel plate and a trailing steel plate, the plate thickness measuring step of measuring the thickness of each welded portion of the leading steel plate and the trailing steel plate, and the preceding steel plate. After welding to determine the post-heating current value for heating the welded portion after the butt welding based on the plate thickness measured in the plate thickness measuring step and the welding step of butt-welding the trailing steel plate. A butt welding method for steel plates, which comprises a determination step and a step of heating each of the welded portions based on the post-heating current value determined in the post-heating determination step.
[2] In the post-heating determination step, the average measurement of the plate thickness of the welded portion of the preceding steel sheet and the plate thickness of the welded portion of the trailing steel plate measured in the plate thickness measuring step. The butt welding method for steel sheets according to [1], wherein the post-heating current value is determined based on the plate thickness.
[3] In the post-heating determination step, the following formula (1) is satisfied based on the preset post-heating current value, the average set plate thickness of the leading steel plate and the trailing steel plate, and the average measuring plate thickness. The butt welding method for steel sheets according to [1] or [2], wherein the post-heating current value is determined so as to be performed.
［４］ 前記先行鋼板と前記後行鋼板の硬度は、ビッカース硬さが１００ＨＶ以上１０００ＨＶ以下である、［１］〜［３］のいずれかに記載の鋼板の突合せ溶接方法。
［５］ 前記先行鋼板と前記後行鋼板との突合せ溶接により形成された溶接部の硬度は、ビッカース硬さが１００ＨＶ以上１０００ＨＶ以下である、［１］〜［４］のいずれかに記載の鋼板の突合せ溶接方法。
［６］ 先行鋼板および後行鋼板は、質量％で、Ｃ：０．５％以上、
Ｓｉ：０．１％以上０．５％以下、
Ｍｎ：０．３％以上０．６％以下、
Ｐ：０．０５％以下、
Ｓ：０．０５％以下、
Ｃｕ：０．５％以下、
Ｎｉ：３％以下、
Ｃｒ：０．０５％以上０．５％以下、
Ａｌ：０．０５％以下、
残部Ｆｅおよび不可避的不純物からなる成分組成を有する、［１］〜［５］のいずれかに記載の鋼板の突合せ溶接方法。
［７］ 先行鋼板および後行鋼板は、質量％で、Ｃ：０．５％以上２．２％以下、
Ｓｉ：０．１％以上０．５％以下、
Ｍｎ：０．３％以上０．６％以下、
Ｐ：０．０５％以下、
Ｓ：０．０５％以下、
Ｃｕ：０．５％以下、
Ｎｉ：３％以下、
Ｃｒ：０．０５％以上０．５％以下、
Ａｌ：０．０５％以下、
残部Ｆｅおよび不可避的不純物からなる成分組成を有する、［６］に記載の鋼板の突合せ溶接方法。
［８］ 前記突合せ溶接は、レーザー溶接方法である、［１］〜［７］のいずれかに記載の鋼板の突合せ溶接方法。
[4] The butt welding method for steel sheets according to any one of [1] to [3], wherein the hardness of the leading steel sheet and the trailing steel sheet is 100 HV or more and 1000 HV or less in Vickers hardness.
[5] The steel plate according to any one of [1] to [4], wherein the hardness of the welded portion formed by the butt welding of the leading steel plate and the trailing steel plate is 100 HV or more and 1000 HV or less in Vickers hardness. Butt welding method.
[6] The leading steel sheet and the trailing steel sheet are in mass%, C: 0.5% or more,
Si: 0.1% or more and 0.5% or less,
Mn: 0.3% or more and 0.6% or less,
P: 0.05% or less,
S: 0.05% or less,
Cu: 0.5% or less,
Ni: 3% or less,
Cr: 0.05% or more and 0.5% or less,
Al: 0.05% or less,
The butt welding method for a steel sheet according to any one of [1] to [5], which has a component composition consisting of the balance Fe and unavoidable impurities.
[7] The leading steel sheet and the trailing steel sheet are in mass%, C: 0.5% or more and 2.2% or less.
Si: 0.1% or more and 0.5% or less,
Mn: 0.3% or more and 0.6% or less,
P: 0.05% or less,
S: 0.05% or less,
Cu: 0.5% or less,
Ni: 3% or less,
Cr: 0.05% or more and 0.5% or less,
Al: 0.05% or less,
The butt welding method for a steel sheet according to [6], which has a component composition consisting of the balance Fe and unavoidable impurities.
[8] The butt welding method according to any one of [1] to [7], which is a laser welding method.
本発明によれば、後加熱処理条件のうち後加熱電流値を変化させることで、板厚変動を考慮して後加熱不足や後加熱過多を防ぎ、安定的に溶接部の後加熱処理を行うことができるため、鋼板を圧延した際に溶接部の破断トラブル発生を回避し、コイルの生産性を向上させることができる。 According to the present invention, by changing the post-heating current value among the post-heat treatment conditions, it is possible to prevent insufficient post-heating and excessive post-heating in consideration of plate thickness fluctuations, and to stably perform post-heat treatment of the welded portion. Therefore, it is possible to avoid the occurrence of breakage troubles in the welded portion when the steel sheet is rolled and improve the productivity of the coil.
本発明の好ましい実施形態を以下に述べる。
本発明の鋼板の突合せ溶接方法は、鋼帯の端部である先行鋼板と別の鋼帯の端部である後行鋼板とを突合せ溶接する方法であって、先行鋼板と後行鋼板のそれぞれの溶接部となる部分の板厚を測定する板厚測定工程と、先行鋼板と後行鋼板とを突合せ溶接する溶接工程と、板厚測定工程で測定された上記板厚に基づいて突合せ溶接後に上記溶接部を加熱するための後加熱電流値を決定する後加熱決定工程と、後加熱決定工程で決定した後加熱電流値に基づいて上記溶接部を加熱する工程（後加熱工程ともいう）とを含む。
図２は、本発明の突合せ溶接方法のフローを表す図である。本発明の鋼板の突合せ溶接方法は、図２に示すような順番にて実施されることが好ましいが、溶接工程と後加熱決定工程の順番が入れ替わっていてもよい。または、溶接工程、板厚測定工程、後加熱決定工程、後加熱工程の順に行うことも可能である。
Preferred embodiments of the present invention are described below.
The butt welding method of the steel plate of the present invention is a method of butt welding the leading steel plate which is the end of the steel strip and the trailing steel plate which is the end of another steel strip, and the leading steel plate and the trailing steel plate are respectively. After the plate thickness measurement step of measuring the plate thickness of the portion to be the welded portion, the welding process of butt welding the leading steel plate and the trailing steel plate, and the butt welding based on the plate thickness measured in the plate thickness measuring process. A post-heating determination step of determining the post-heating current value for heating the welded portion and a step of heating the welded portion based on the post-heating current value determined in the post-heating determination step (also referred to as a post-heating step). including.
FIG. 2 is a diagram showing a flow of the butt welding method of the present invention. The butt welding method for steel sheets of the present invention is preferably carried out in the order shown in FIG. 2, but the order of the welding step and the post-heating determination step may be interchanged. Alternatively, the welding step, the plate thickness measuring step, the post-heating determination step, and the post-heating step can be performed in this order.
本発明において、熱間圧延工程において製造された鋼帯を用いて、冷間圧延工程における鋼帯の先行鋼板と別の鋼帯の後行鋼板を接合する際の、最適な後加熱決定条件を見出すことに特徴を有する。
本発明において、先行鋼板とは、溶接工程において製造ラインを先行する鋼帯を指し、後行鋼板とは先行鋼板の直後に配置される別の鋼帯を指す。
本発明において、図３（ａ）及び（ｂ）に示すように、後加熱処理装置がレーザー溶接装置と一体となった装置を用いてもよい。後加熱処理装置３０が一体となったレーザー溶接装置２０では、アジャスティングロール、加工ヘッド、バックロール、スエージングロール（図示なし）と、後加熱処理装置３０が一体で動作する。例えば図３（ａ）および（ｂ）に示すように、レーザー溶接装置２０と後加熱処理装置３０は冷間圧延工程における鋼帯の先行鋼板１０と別の鋼帯の後行鋼板１１の溶接部５０になる端部に対して、上下に配置される。レーザー溶接装置２０が図３（ａ）中の矢印の方向に進むことにより、先行鋼板１０と後行鋼板１１が突合せ溶接されるとともに、後加熱処理装置３０によって溶接部５０が後加熱処理される。
なお、ここで用いる先行鋼板と後行鋼板の溶接部にあたる鋼板の端部は、図１からわかるように、板厚が端部で大きく変動していることがわかる。この箇所で溶接を行った場合、予め設定された板厚よりも端部の板厚が大きい場合は後加熱不足になり、予め設定された板厚よりも端部の板厚が小さい場合は後加熱過多となり、最適な後加熱の熱量の範囲（合格範囲）を外れてしまうことがある。そこで本発明者は、平均設定板厚（一組の先行鋼板と後行鋼板の予め設定されている板厚を平均化した値。後述の平均設定板厚の算出方法を参照。）２．０ｍｍ〜２．５ｍｍにおいて、電流値（Ａ）５０Ａ〜１３０Ａの範囲で１０Ａずつ電流値を変えて、エリクセン試験後の試験片の溶接部の割れ方が合格範囲内となる最適な平均設定板厚と電流値の相関関係を調べた。結果を図４に示す。
図４は、Ｘ軸を平均設定板厚（ｍｍ）、Ｙ軸を後加熱の電流値（Ａ）として、高炭素当量材のエリクセン試験後の試験片の溶接部の割れ方が合格範囲内となる、最適な平均設定板厚と電流値の相関関係を示す図である。図４に示すように、平均設定板厚２．０ｍｍでは、電流値９０Ａが最適（図中〇で示される）であり、平均設定板厚が２．２５ｍｍでは、電流値９０〜１００Ａが最適（図中〇で示される）であり、平均設定板厚が２．５ｍｍでは、電流値９０〜１００Ａが最適（図中〇で示される）な電流値であった。図４より、それぞれの平均板厚に対する後加熱電流値が合格範囲内（図中の〇で示される箇所）であれば割れ方に問題がなく、鋼帯を圧延した場合に生じ得る溶接部の破断トラブルの発生を防ぐことが出来る。一方、合格範囲外（図中の×で示される箇所）であると、割れ方に問題があり、鋼帯を圧延した場合、溶接部の破断トラブルの発生の原因となる。
In the present invention, the optimum post-heating determination conditions for joining the leading steel plate of the steel strip and the trailing steel plate of another steel strip in the cold rolling process using the steel strip manufactured in the hot rolling process are determined. It is characterized by finding it.
In the present invention, the leading steel plate refers to a steel strip that precedes the production line in the welding process, and the trailing steel plate refers to another steel strip that is arranged immediately after the leading steel plate.
In the present invention, as shown in FIGS. 3A and 3B, an apparatus in which the post-heat treatment apparatus is integrated with the laser welding apparatus may be used. In the laser welding apparatus 20 in which the post-heat treatment apparatus 30 is integrated, the adjusting roll, the processing head, the back roll, the aging roll (not shown) and the post-heat treatment apparatus 30 operate integrally. For example, as shown in FIGS. 3A and 3B, the laser welding apparatus 20 and the post-heat treatment apparatus 30 are welded portions of the leading steel plate 10 of the steel strip and the trailing steel plate 11 of another steel strip in the cold rolling process. It is arranged vertically with respect to the end portion which becomes 50. When the laser welding apparatus 20 advances in the direction of the arrow in FIG. 3A, the leading steel plate 10 and the trailing steel plate 11 are butt-welded, and the welded portion 50 is post-heat-treated by the post-heat treatment apparatus 30. ..
As can be seen from FIG. 1, it can be seen that the thickness of the end portion of the steel plate, which is the welded portion between the leading steel plate and the trailing steel plate, used here varies greatly at the end portion. When welding is performed at this point, if the plate thickness at the end is larger than the preset plate thickness, the post-heating will be insufficient, and if the plate thickness at the end is smaller than the preset plate thickness, the post-heating will be insufficient. Excessive heating may result in a deviation from the optimum range of heat after heating (passing range). Therefore, the present inventor has an average set plate thickness (a value obtained by averaging the preset plate thicknesses of a set of leading steel plates and trailing steel plates. See the method for calculating the average set plate thickness described later) 2.0 mm. At ~ 2.5 mm, the current value (A) is changed by 10 A in the range of 50 A to 130 A to obtain the optimum average set thickness within the acceptable range for cracking of the welded part of the test piece after the Ericssen test. The correlation between the current values was investigated. The results are shown in FIG.
In FIG. 4, the X-axis is the average set plate thickness (mm), the Y-axis is the post-heating current value (A), and the cracking of the welded part of the test piece after the Eriksen test of the high carbon equivalent material is within the acceptable range. It is a figure which shows the correlation of the optimum average setting plate thickness and a current value. As shown in FIG. 4, when the average set plate thickness is 2.0 mm, the current value of 90 A is optimal (indicated by ◯ in the figure), and when the average set plate thickness is 2.25 mm, the current value of 90 to 100 A is optimal (indicated by ◯). (Indicated by ◯ in the figure), and when the average set plate thickness was 2.5 mm, the current value of 90 to 100 A was the optimum current value (indicated by ◯ in the figure). From FIG. 4, if the post-heating current value for each average plate thickness is within the acceptable range (the part indicated by ◯ in the figure), there is no problem in the cracking method, and the welded portion that may occur when the steel strip is rolled. It is possible to prevent the occurrence of breakage trouble. On the other hand, if it is out of the pass range (the part indicated by x in the figure), there is a problem in the cracking method, and when the steel strip is rolled, it causes a fracture trouble of the welded portion.
板厚測定工程とは、溶接前に、先行鋼板及び後行鋼板の溶接部となる部分の板厚を測定することである。なお、板厚測定工程は、先行鋼板及び後行鋼板それぞれの幅中央１点を測定する方法や（図５参照）、溶接機に付随した板厚計で溶接部の全幅を測定する方法がある。例えば、先行鋼板及び後行鋼板それぞれの幅中央１点を測定する方法の場合、図５に示すような、鋼帯の上下を挟み込むレーザー変位計である板厚計４０を用いて、先行鋼板１０および後行鋼板１１それぞれの幅中央１点の板厚を測定すればよい。また、溶接機に付随した板厚計で溶接部の全幅の板厚を測定する方法の場合、測定された全幅の板厚のうち、任意の複数の位置における板厚を、後加熱電流値を決定するための板厚として用いればよい。例えば、幅方向３点の板厚を用いて後加熱電流値を決定する方法が例示される。
板厚測定工程で測定された先行鋼板の溶接部となる部分の板厚と、後行鋼板の溶接部となる部分の板厚との平均測定板厚に基づいて後加熱電流値を決定することにより、最適な熱量で溶接部の後加熱処理を行うことができ、鋼帯を圧延した場合に生じうる溶接部の破断トラブルの発生を防ぐことが出来る。なお、先行鋼板および後行鋼板の溶接部となる部分の板厚とは、図５に示すように、先行鋼板および後行鋼板の端部の板厚（図５の５０−１、５０−２）のことをいう。
The plate thickness measuring step is to measure the plate thickness of the portion to be the welded portion of the leading steel plate and the trailing steel plate before welding. In the plate thickness measuring step, there are a method of measuring one point at the center of the width of each of the leading steel plate and the trailing steel plate (see FIG. 5), and a method of measuring the total width of the welded portion with a plate thickness gauge attached to the welding machine. .. For example, in the case of the method of measuring one point at the center of the width of each of the leading steel plate and the trailing steel plate, the leading steel plate 10 is used as a plate thickness gauge 40 which is a laser displacement meter that sandwiches the upper and lower parts of the steel strip as shown in FIG. And the plate thickness at one point in the center of the width of each of the trailing steel plates 11 may be measured. Further, in the case of the method of measuring the plate thickness of the entire width of the welded portion with a plate thickness gauge attached to the welding machine, the plate thickness at any plurality of positions among the measured plate thicknesses of the total width is measured, and the postheating current value is measured. It may be used as a plate thickness for determining. For example, a method of determining the post-heating current value using the plate thickness at three points in the width direction is exemplified.
The post-heating current value is determined based on the average measured plate thickness of the welded portion of the leading steel plate and the welded portion of the trailing steel plate measured in the plate thickness measuring process. Therefore, the post-heat treatment of the welded portion can be performed with an optimum amount of heat, and it is possible to prevent the occurrence of breakage trouble of the welded portion that may occur when the steel strip is rolled. As shown in FIG. 5, the thickness of the portion to be the welded portion of the leading steel plate and the trailing steel plate is the thickness of the end portion of the leading steel plate and the trailing steel plate (50-1, 50-2 in FIG. 5). ).
本発明の溶接工程は、先行鋼板と後行鋼板とを突合せ溶接する工程である。本発明の連続圧延ラインに適用される溶接方法は、レーザー溶接を用いることが好ましい。
本発明におけるレーザー溶接は、鋼板を突合せ、鋼板間を０．２ｍｍ未満とし、鋼板間にワイヤーを送りながら、レーザーで鋼板及びワイヤーを溶かし込みながら溶接する。
レーザー溶接は、エネルギー密度が高く入熱量が少ないため、フラッシュバット溶接に比べて優れた品質特性が得られる。しかしながら、高炭素当量材などを用いる溶接では、溶接後の急冷により、溶接部に硬化した低温変態組織（マルテンサイト、ベイナイトが含まれた組織）が発生するため溶接部に亀裂が発生し、溶接部の破断トラブルの原因となってしまう。この溶接部の硬化に対しては、溶接後に加熱する後加熱を行うことで、硬化した溶接部を焼戻し、軟化させて溶接部の破断トラブル発生を防止することが知られている。
The welding process of the present invention is a process of butt welding a leading steel sheet and a trailing steel sheet. Laser welding is preferably used as the welding method applied to the continuous rolling line of the present invention.
In the laser welding in the present invention, the steel plates are butted so that the distance between the steel plates is less than 0.2 mm, and the steel plates and the wires are melted and welded with a laser while feeding the wires between the steel plates.
Since laser welding has a high energy density and a small amount of heat input, excellent quality characteristics can be obtained as compared with flash butt welding. However, in welding using a high carbon equivalent material, etc., quenching after welding causes a hardened low-temperature transformation structure (structure containing martensite and bainite) to occur in the welded part, causing cracks in the welded part and welding. It may cause a trouble of breaking the part. It is known that the cured welded portion is tempered and softened by heating after welding to prevent the welded portion from breaking.
本発明において、先行鋼板および後行鋼板は、質量％で、Ｃ：０．５％以上、Ｓｉ：０．１％以上０．５％以下、Ｍｎ：０．３％以上０．６％以下、Ｐ：０．０５％以下、Ｓ：０．０５％以下、Ｃｕ：０．５％以下、Ｎｉ：３％以下、Ｃｒ：０．０５％以上０．５％以下、Ａｌ：０．０５％以下、残部Ｆｅおよび不可避的不純物からなる成分組成を有することが好ましく、このような成分組成を有する先行鋼板と後行鋼板を溶接することで、発生する低温変態組織起因の溶接部の破断トラブルを防止するためのものである。なお、Ｃ量については、２．２％以下であることがより好ましい。また、不可避的不純物としては、例えば、Ｎ、Ｔｉ、Ｎｂ、Ｖ、Ｗ、Ｂ、Ｍｏ、Ｚｒ、Ｓｎ、Ｓｂ、Ｔａ、Ｃａ、Ｍｇ、Ｃｅ、Ｌａ、ＲＥＭ等が挙げられ、これらの含有量は、合計で０．５質量％以下であれば許容できる。 In the present invention, the leading steel sheet and the trailing steel sheet are C: 0.5% or more, Si: 0.1% or more and 0.5% or less, Mn: 0.3% or more and 0.6% or less in mass%. P: 0.05% or less, S: 0.05% or less, Cu: 0.5% or less, Ni: 3% or less, Cr: 0.05% or more and 0.5% or less, Al: 0.05% or less It is preferable to have a component composition consisting of the balance Fe and unavoidable impurities, and by welding the leading steel sheet and the trailing steel sheet having such a component composition, the trouble of breaking the welded portion due to the low temperature transformation structure that occurs is prevented. It is for doing. The amount of C is more preferably 2.2% or less. Examples of unavoidable impurities include N, Ti, Nb, V, W, B, Mo, Zr, Sn, Sb, Ta, Ca, Mg, Ce, La, REM and the like, and their contents. Is acceptable as long as it is 0.5% by mass or less in total.
なお、先行鋼板と後行鋼板の硬度は、ビッカース硬さが１００ＨＶ以上１０００ＨＶ以下であると好ましく、１００ＨＶ以上４００ＨＶ以下であるとより好ましく、１００ＨＶ以上２００ＨＶ以下であると更に好ましい。上記範囲内であると、溶接部の破断トラブルが発生しにくい。
また、先行鋼板と後行鋼板との突合せ溶接により形成された溶接部の硬度は、ビッカース硬さが１００ＨＶ以上１０００ＨＶ以下であると好ましく、１００ＨＶ以上４００ＨＶ以下であるとより好ましく、１００ＨＶ以上２００ＨＶ以下であると更に好ましい。上記範囲内であると、先行鋼板および後行鋼板と溶接部の硬度差が小さいため、溶接部の破断トラブルが発生しにくい。
なお、上述のビッカース硬さは、ＪＩＳ Ｚ２２４４：２００９に基づいて測定すればよい。
The hardness of the leading steel plate and the trailing steel plate is preferably 100 HV or more and 1000 HV or less, more preferably 100 HV or more and 400 HV or less, and further preferably 100 HV or more and 200 HV or less. If it is within the above range, the trouble of breaking the welded portion is unlikely to occur.
Further, the hardness of the welded portion formed by the butt welding of the leading steel plate and the trailing steel plate is preferably 100 HV or more and 1000 HV or less, more preferably 100 HV or more and 400 HV or less, and 100 HV or more and 200 HV or less. It is more preferable to have it. If it is within the above range, the hardness difference between the leading steel plate and the trailing steel plate and the welded portion is small, so that the trouble of breaking the welded portion is unlikely to occur.
The Vickers hardness described above may be measured based on JIS Z2244: 2009.
鋼板の材料となる高炭素当量材は、炭素当量の多い鋼種ほどマルテンサイト化されるため、溶接部のみ硬化してその他の鋼板の箇所との硬度差が生じる。よって、溶接部を後加熱処理することで、焼戻しマルテンサイトとして軟化させ、溶接部と鋼板の硬度差を低下させることが好ましい。したがって、本発明では、先行鋼板と後行鋼板との突合せ溶接により形成された溶接部の硬度は、ビッカース硬さが１００ＨＶ以上１０００ＨＶ以下であることが好ましい。 As for the high carbon equivalent material used as the material of the steel sheet, the higher the carbon equivalent of the steel type, the more martensite is formed. Therefore, only the welded portion is hardened and a hardness difference from other steel sheet parts occurs. Therefore, it is preferable that the welded portion is post-heated to soften it as tempered martensite and reduce the difference in hardness between the welded portion and the steel sheet. Therefore, in the present invention, the hardness of the welded portion formed by the butt welding of the leading steel plate and the trailing steel plate is preferably a Vickers hardness of 100 HV or more and 1000 HV or less.
後加熱処理において、溶接部の板厚変動を考慮せずに均一な熱量で溶接部に後加熱処理を適用させると、予め設定された板厚よりも厚い場合の後加熱不足や、予め設定された板厚よりも薄い場合の後加熱過多を防ぐことが難しい。このような場合、最適な後加熱の熱量の範囲（合格範囲ともいう）を外れてしまい、安定的に後加熱処理を行うことや、板を圧延した際に溶接部の破断トラブル発生を回避できず、コイルの生産性が低下する。 In the post-heat treatment, if the post-heat treatment is applied to the weld with a uniform amount of heat without considering the fluctuation of the plate thickness of the weld, the post-heat is insufficient when the plate thickness is thicker than the preset thickness, or the post-heat treatment is preset. It is difficult to prevent overheating when the thickness is thinner than the plate thickness. In such a case, the range of the optimum amount of heat for post-heating (also referred to as the pass range) is deviated, and stable post-heating treatment can be performed and troubles such as breakage of the welded portion can be avoided when the plate is rolled. However, the productivity of the coil is reduced.
そこで、本発明は後加熱処理において、均一な熱量で溶接部に後加熱処理をするのではなく、板厚測定工程で測定された板厚に基づいて、突合せ溶接後に溶接部を加熱するための後加熱電流値を決定し、溶接部を加熱する。
本発明の後加熱決定工程において、板厚測定工程で測定された先行鋼板の溶接部となる部分の板厚と、後行鋼板の溶接部となる部分の板厚との平均測定板厚に基づいて後加熱電流値を決定する工程である。
Therefore, in the post-heat treatment, the present invention does not perform post-heat treatment on the welded portion with a uniform amount of heat, but heats the welded portion after butt welding based on the plate thickness measured in the plate thickness measuring step. The post-heating current value is determined and the weld is heated.
In the post-heating determination step of the present invention, based on the average measured plate thickness of the welded portion of the preceding steel plate and the plate thickness of the welded portion of the trailing steel plate measured in the plate thickness measuring step. This is the process of determining the post-heating current value.
はじめに、一組の先行鋼板と後行鋼板の予め設定されている板厚を平均化して平均板厚を算出する（平均設定板厚）。そして、その平均設定板厚を後加熱する場合の電流値も割り出す（平均設定電流、すなわち予め設定された後加熱電流値）。
次に、上記の先行鋼板と上記の後行鋼板の測定板厚を平均化して平均測定板厚を算出する。
ここでの平均化とは、先行鋼板と後行鋼板の板厚を足して２で割ることを云う。
最後に、下記式（３）に表される後加熱温度算出式の中の板厚（ｌ）、後加熱電流値（Ｉ）を基に下記式（２）を導きだす。次に、下記式（２）を基にして下記式（１）に平均設定板厚、平均設定電流、平均測定板厚を代入して、後加熱電流値を算出する。後加熱電流値とは、前述の通り導かれた電流値であり、後加熱処理に用いられる電流値である。
上記手順により算出された後加熱電流値を後加熱処理条件とし、各溶接部の後加熱処理を行う。
First, the average plate thickness is calculated by averaging the preset plate thicknesses of a set of leading steel plates and trailing steel plates (average set plate thickness). Then, the current value when the average set plate thickness is post-heated is also calculated (average set current, that is, the preset post-heating current value).
Next, the average measurement plate thickness is calculated by averaging the measurement plate thicknesses of the preceding steel plate and the trailing steel plate.
The averaging here means adding the thicknesses of the leading steel plate and the trailing steel plate and dividing by two.
Finally, the following formula (2) is derived based on the plate thickness (l) and the post-heating current value (I) in the post-heating temperature calculation formula represented by the following formula (3). Next, based on the following formula (2), the average set plate thickness, the average set current, and the average measurement plate thickness are substituted into the following formula (1) to calculate the post-heating current value. The post-heating current value is a current value derived as described above, and is a current value used for post-heating treatment.
The post-heat treatment is performed using the post-heating current value calculated by the above procedure as the post-heat treatment condition.
上記の通り算出された後加熱電流値を後加熱処理条件とし、溶接部を加熱する工程を行う。先行鋼板、後行鋼板それぞれの幅中央１点のみ測定した場合は、後加熱電流値の算出及び設定は一度行えば後加熱処理条件を得ることが出来るが、溶接機に板厚計を付随させた場合は、複数回算出及び設定を行う必要がある。なお、本発明において、式（１）により算出される後加熱電流値の±１０％以内を後加熱熱処理条件とすることが好ましく、±５％以内がより好ましい
本発明の後加熱処理は、誘導加熱による後加熱処理装置にて行われることが好ましい。
本発明に用いられたレーザー溶接装置の仕様は、発振器出力１２ｋＷ、発振器モード：低次マルチモード（ＴＥＭ０１）、シールドガス：ＣＯ２ガスであるが、この仕様に限定されない。
また、本発明に用いられた後加熱処理装置の仕様は、高周波誘電コイルを使用した装置で、加熱面積が７２ｍｍ×３８０ｍｍ、定格出力４０ｋＷ、周波数３０ｋＨｚ、加熱方法は移動式であるが、この仕様に限定されない。
The step of heating the welded portion is performed using the post-heating current value calculated as described above as the post-heat treatment condition. If only one point in the center of the width of each of the leading steel plate and the trailing steel plate is measured, the post-heating treatment conditions can be obtained by calculating and setting the post-heating current value once, but a plate thickness gauge is attached to the welding machine. In that case, it is necessary to calculate and set multiple times. In the present invention, the post-heating heat treatment condition is preferably within ± 10% of the post-heating current value calculated by the formula (1), more preferably within ± 5%. The post-heat treatment of the present invention is induced. It is preferably performed in a post-heat treatment apparatus by heating.
The specifications of the laser welding apparatus used in the present invention are, but are not limited to, an oscillator output of 12 kW, an oscillator mode: low-order multimode (TEM01), and a shield gas: CO 2 gas.
The specifications of the post-heat treatment apparatus used in the present invention are an apparatus using a high-frequency dielectric coil, having a heating area of 72 mm × 380 mm, a rated output of 40 kW, a frequency of 30 kHz, and a mobile heating method. Not limited to.
誘導加熱にて後加熱を行う場合、後加熱処理条件として、後加熱時の温度ではなく上記の後加熱決定工程に基づいて算出された後加熱時の電流値（熱量）を適用して後加熱を行う。そのため、最適な後加熱温度が同じである鋼板であっても、最適な電流値は鋼板の厚さによってそれぞれ異なるため、溶接部ごとに電流値を設定している。 When post-heating is performed by induction heating, the post-heating current value (calorific value) calculated based on the above post-heating determination step is applied as the post-heating treatment condition instead of the post-heating temperature. I do. Therefore, even for steel sheets having the same optimum post-heating temperature, the optimum current value differs depending on the thickness of the steel sheet, so the current value is set for each welded portion.
本発明による好ましい実施例について説明するが、下記に限定されたものではない。 Preferred examples according to the present invention will be described, but the present invention is not limited to the following.
成分組成として、質量％で、Ｃ：０．９５％、Ｓｉ：０．２％、Ｍｎ：０．４５％、Ｐ：０．０１％、Ｓ：０．０１％、Ｃｕ：０．０８％、Ｎｉ：０．０８％、Ｃｒ：０．２％、Ａｌ：０．０１％、残部Ｆｅおよび不可避的不純物を含有する鋼板を、先行鋼板および後行鋼板として用いた。
先行鋼板１０と後行鋼板１１の予め設定した板厚を平均化した平均設定板厚と、先行鋼板と後行鋼板の端部の幅中央を板厚計４０を用いて測定し、これらを平均化した平均測定板厚の結果を、下記表１に示す。
板厚計４０では、鋼板と垂直になるように上下からレーザーを照射して、レーザー照射口から鋼板の表面までの距離から板厚を測定する。
また、予め設定された後加熱電流は、１００Ａと設定した。
As the component composition, in mass%, C: 0.95%, Si: 0.2%, Mn: 0.45%, P: 0.01%, S: 0.01%, Cu: 0.08%, A steel sheet containing Ni: 0.08%, Cr: 0.2%, Al: 0.01%, the balance Fe and unavoidable impurities was used as the leading steel sheet and the trailing steel sheet.
The average set plate thickness obtained by averaging the preset plate thicknesses of the leading steel plate 10 and the trailing steel plate 11 and the center width of the ends of the leading steel plate and the trailing steel plate are measured using a plate thickness meter 40, and these are averaged. The results of the average measured plate thickness are shown in Table 1 below.
In the plate thickness meter 40, the laser is irradiated from above and below so as to be perpendicular to the steel plate, and the plate thickness is measured from the distance from the laser irradiation port to the surface of the steel plate.
Further, the preset heating current was set to 100 A.
先行鋼板１０と後行鋼板１１の平均設定板厚、及び、先行鋼板１０と後行鋼板１１の平均測定板厚と、予め設定された後加熱電流値１００Ａを、上記で説明した式（１）に代入し、後加熱電流値を算出したところ、１１０Ａと算出された。 The average set plate thickness of the leading steel plate 10 and the trailing steel plate 11, the average measured plate thickness of the leading steel plate 10 and the trailing steel plate 11, and the preset post-heating current value of 100 A are expressed by the equation (1) described above. When the post-heating current value was calculated by substituting into, it was calculated as 110A.
得られた後加熱電流値（１１０Ａ）を後加熱処理装置３０の後加熱処理条件とし、先行鋼板１０と後行鋼板１１を、図３に示すようなレーザー溶接装置２０と後加熱処理装置３０とが一体化された一体型レーザー溶接機にて溶接した後、後加熱処理装置３０で１１０Ａの誘導加熱を当てながら鋼帯１の溶接部５０を後加熱処理した。 The obtained post-heating current value (110A) is used as the post-heat treatment condition of the post-heat treatment apparatus 30, and the leading steel plate 10 and the trailing steel plate 11 are combined with the laser welding apparatus 20 and the post-heat treatment apparatus 30 as shown in FIG. After welding with an integrated laser welder integrated with the above, the welded portion 50 of the steel strip 1 was post-heat-treated while applying induction heating of 110A with the post-heat treatment device 30.
後加熱処理後の試験片について、溶接部の成形性を判断した。溶接部の成形性を判定するには、主にエリクセン試験で確認した。
エリクセン試験では、先行鋼板と後行鋼板の溶接部を含む試験片を、エリクセン試験機のダイス上に置き、その中央に半球状のポンチを押し込んでダイスで絞りだし、試験片に少なくとも１か所の亀裂が生じるまでポンチを進入させて、溶接部の割れ方を目視にて判定した。
試験結果は、以下に示す判定にて評価した。表２にエリクセン試験の判定基準を示す。
○： 溶接に対して垂直割れ
△： 一部溶接割れ
×： 溶接割れ
The formability of the welded portion was judged for the test piece after the post-heat treatment. In order to judge the formability of the welded part, it was mainly confirmed by the Eriksen test.
In the Eriksen test, a test piece containing the welded portion of the leading steel plate and the trailing steel plate is placed on the die of the Eriksen testing machine, a hemispherical punch is pushed into the center of the test piece, and the test piece is squeezed out with a die. The punch was inserted until the crack was generated, and the cracking method of the weld was visually determined.
The test results were evaluated by the judgments shown below. Table 2 shows the criteria for the Eriksen test.
◯: Vertical crack with respect to welding △: Partial welding crack ×: Welding crack
得られた後加熱電流値（１１０Ａ）で後加熱を行ったところ、溶接部の割れ方は〇であり、本発明を満足した。
また、平均設定板厚の異なる試験片を用意し、後加熱電流値を後加熱処理装置３０の条件とし、先行鋼板１０と後行鋼板１１を溶接後、後加熱処理装置３０の誘導加熱により溶接部を後加熱処理した。後加熱電流値を後加熱処理装置３０の後加熱処理条件と設定して溶接した試験片は、溶接部に対して垂直割れをおこし（判定「○」）、溶接部が強固に溶接されていることが判明した。
一方、後加熱電流値を後加熱処理装置３０の後加熱処理条件と設定しなかったものは、溶接部に対して垂直割れしたサンプルに混じって、溶接部に沿って割れた試験片や（判定「×」）、一部溶接割れした試験片（判定「△」）が混在してしまい、溶接部の成形性が安定しなかった。
When post-heating was performed with the obtained post-heating current value (110 A), the cracking of the welded portion was ◯, which satisfied the present invention.
Further, test pieces having different average set plate thicknesses are prepared, the post-heating current value is set as the condition of the post-heat treatment device 30, the leading steel plate 10 and the trailing steel plate 11 are welded, and then welded by induction heating of the post-heat treatment device 30. The part was post-heat treated. The test piece welded with the post-heating current value set as the post-heat treatment condition of the post-heat treatment apparatus 30 causes vertical cracks with respect to the welded portion (judgment "○"), and the welded portion is firmly welded. It has been found.
On the other hand, those in which the post-heating current value was not set as the post-heat treatment condition of the post-heat treatment apparatus 30 were mixed with the sample cracked perpendicular to the welded portion and cracked along the welded portion (judgment). “X”) and a test piece that was partially cracked by welding (judgment “Δ”) were mixed, and the moldability of the welded portion was not stable.
１ 鋼帯
１０ 先行鋼板
１１ 後行鋼板
２０ レーザー溶接装置
３０ 後加熱処理装置
４０ 板厚計
５０ 溶接部
５０−１ 先行鋼板の溶接部となる部分の板厚（先行鋼板の端部の板厚）
５０−２ 後行鋼板の溶接部となる部分の板厚（後行鋼板の端部の板厚）
1 Steel strip 10 Leading steel plate 11 Trailing steel plate 20 Laser welding device 30 Post-heat treatment device 40 Plate thickness gauge 50 Welded portion 50-1 Plate thickness of the portion to be the welded portion of the preceding steel plate (plate thickness at the end of the preceding steel plate)
50-2 Thickness of the welded part of the trailing steel plate (thickness of the end of the trailing steel plate)
Claims (8)
前記先行鋼板と前記後行鋼板のそれぞれの溶接部となる部分の板厚を測定する板厚測定工程と、
前記先行鋼板と前記後行鋼板とを突合せ溶接する溶接工程と、
前記板厚測定工程で測定された前記板厚に基づいて前記突合せ溶接後に前記溶接部を加熱するための後加熱電流値を決定する後加熱決定工程と、
前記後加熱決定工程で決定した前記後加熱電流値に基づいて前記それぞれの溶接部を加熱する工程と、を含む、鋼板の突合せ溶接方法。 It is a method of butt welding the leading steel sheet and the trailing steel sheet.
A plate thickness measuring step for measuring the thickness of each welded portion of the leading steel plate and the trailing steel plate, and
A welding process in which the leading steel plate and the trailing steel plate are butt-welded,
A post-heating determination step of determining a post-heating current value for heating the welded portion after the butt welding based on the plate thickness measured in the plate thickness measuring step.
A butt welding method for steel sheets, which comprises a step of heating each of the welded portions based on the post-heating current value determined in the post-heating determination step.
Ｓｉ：０．１％以上０．５％以下、
Ｍｎ：０．３％以上０．６％以下、
Ｐ：０．０５％以下、
Ｓ：０．０５％以下、
Ｃｕ：０．５％以下、
Ｎｉ：３％以下、
Ｃｒ：０．０５％以上０．５％以下、
Ａｌ：０．０５％以下、
残部Ｆｅおよび不可避的不純物からなる成分組成を有する、請求項１〜５のいずれか一項に記載の鋼板の突合せ溶接方法。 The leading steel sheet and the trailing steel sheet are in mass%, C: 0.5% or more,
Si: 0.1% or more and 0.5% or less,
Mn: 0.3% or more and 0.6% or less,
P: 0.05% or less,
S: 0.05% or less,
Cu: 0.5% or less,
Ni: 3% or less,
Cr: 0.05% or more and 0.5% or less,
Al: 0.05% or less,
The butt welding method for a steel sheet according to any one of claims 1 to 5, which has a component composition consisting of the balance Fe and unavoidable impurities.
Ｓｉ：０．１％以上０．５％以下、
Ｍｎ：０．３％以上０．６％以下、
Ｐ：０．０５％以下、
Ｓ：０．０５％以下、
Ｃｕ：０．５％以下、
Ｎｉ：３％以下、
Ｃｒ：０．０５％以上０．５％以下、
Ａｌ：０．０５％以下、
残部Ｆｅおよび不可避的不純物からなる成分組成を有する、請求項６に記載の鋼板の突合せ溶接方法。 The leading steel sheet and the trailing steel sheet are in mass%, C: 0.5% or more and 2.2% or less,
Si: 0.1% or more and 0.5% or less,
Mn: 0.3% or more and 0.6% or less,
P: 0.05% or less,
S: 0.05% or less,
Cu: 0.5% or less,
Ni: 3% or less,
Cr: 0.05% or more and 0.5% or less,
Al: 0.05% or less,
The butt welding method for a steel sheet according to claim 6, which has a component composition consisting of the balance Fe and unavoidable impurities.
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| CN102717178A (en) * | 2012-05-29 | 2012-10-10 | 武汉钢铁(集团)公司 | Resistance spot welding method used for high-aluminum automobile sheet with 800MPa-level tensile strength |
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