JP2002256335A - Method and device for micro-crystallizing metal structure by laser beam irradiation - Google Patents
Method and device for micro-crystallizing metal structure by laser beam irradiationInfo
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- JP2002256335A JP2002256335A JP2001058489A JP2001058489A JP2002256335A JP 2002256335 A JP2002256335 A JP 2002256335A JP 2001058489 A JP2001058489 A JP 2001058489A JP 2001058489 A JP2001058489 A JP 2001058489A JP 2002256335 A JP2002256335 A JP 2002256335A
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- Prior art keywords
- laser irradiation
- laser
- laser beam
- metal structure
- refining
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、鉄基合金の組織を
微細化する方法および装置に関する。詳しくは、溶接止
端部等疲労亀裂を生じ易い部位や局部的に強度を高くす
る必要がある部位の金属組織を微細化するための方法お
よび装置に関する。The present invention relates to a method and an apparatus for refining the structure of an iron-based alloy. More specifically, the present invention relates to a method and an apparatus for refining a metal structure of a portion where fatigue cracks are easily generated such as a weld toe portion and a portion where local strength needs to be locally increased.
【０００２】[0002]
【従来の技術】従来、加工熱処理制御プロセス（ＴＭＣ
Ｐ：Thermo Mechanical Control Process）等による鉄
基合金組織の微細化技術が知られている。また、近年、
大歪熱間加工と磁場中熱処理を組み合わせたメゾスコピ
ック組織制御技術によって極微細複相組織を得る手段の
実用化が推進されている。このような、金属組織の微細
化によって鉄基合金わけても低炭素鋼は、高抗張力化、
高靱性化の点で大きく進歩した。2. Description of the Related Art Conventionally, a thermomechanical heat treatment control process (TMC
There is known a technique for refining the structure of an iron-based alloy by P (Thermo Mechanical Control Process) or the like. In recent years,
Practical use of means for obtaining an ultrafine multiphase structure by mesoscopic structure control technology combining large strain hot working and heat treatment in a magnetic field has been promoted. Such a low-carbon steel, especially an iron-based alloy, has a high tensile strength,
Great progress has been made in increasing toughness.
【０００３】[0003]
【発明が解決しようとする課題】しかしながら、上記優
れた特性をもつ低炭素鋼等の鉄基合金も、複数の材料を
溶接によって接合すると、溶接継手部の引張強度及び疲
労強度が低下する場合があり、低炭素鋼等の鉄基合金の
高抗張力、高靱性等の優れた特性を活かし切れない問題
がある。また、局部的に強度を高めたい必要性に対して
必ずしも有効な手段がなかった。However, even when an iron-based alloy such as a low carbon steel having the above-mentioned excellent properties is joined by welding a plurality of materials, the tensile strength and fatigue strength of the welded joint may be reduced. There is a problem that it is not possible to take advantage of the excellent properties, such as high tensile strength and high toughness, of iron-based alloys such as low carbon steel. Also, there is no effective means for the need to locally increase the strength.
【０００４】溶接継手部の金属組織を微細化する手段と
して、たとえば特開２０００―３０１３７６号公報に開
示されている溶接ビードの熱処理方法がある。この先行
技術は、溶接トーチと、予熱レーザおよび後加熱レーザ
を同一平面内に整列させ、２つの部品の継手部内で一緒
に移動させて予熱・溶接・後加熱を併せ行うようにした
ものである。この構成によって、予熱レーザによる予熱
スポットおよび後加熱レーザによる後加熱スポットと、
溶接スポットとの温度差を制御し、以て、溶着される溶
接ビードの微細組織を決定せんとするものである。As means for refining the metallographic structure of a weld joint, there is, for example, a heat treatment method for a weld bead disclosed in Japanese Patent Application Laid-Open No. 2000-301376. In this prior art, a welding torch, a preheating laser and a post-heating laser are aligned in the same plane, and are moved together in a joint between two parts to perform preheating, welding and post-heating together. . With this configuration, a preheating spot by a preheating laser and a post-heating spot by a post-heating laser,
The temperature difference from the welding spot is controlled so that the microstructure of the weld bead to be welded is determined.
【０００５】しかしながら、上記先行技術によって到達
し得る結晶粒径は、数十μｍ程度であり、本発明が指向
している数μｍオーダーの微細組織を得ることは不可能
である。本発明は、ＴＭＣＰ等によって得られた微細な
組織を有する高抗張力鋼を溶接によって接合する場合
も、溶接継手部の組織を母材の組織と同等以上に微細化
し、溶接継手部を含む金属材料に機械的特性わけても疲
労強度むらのない構造体を得ることができる金属組織の
微細化方法および装置を提供することを目的とする。However, the crystal grain size that can be achieved by the above-mentioned prior art is about several tens of μm, and it is impossible to obtain a microstructure of the order of several μm, which is intended by the present invention. The present invention is also directed to a method of joining a high tensile strength steel having a fine structure obtained by TMCP or the like, by welding, to make the structure of the weld joint portion finer than or equal to the structure of the base material, and to form a metal material including the weld joint portion. It is another object of the present invention to provide a method and an apparatus for refining a metal structure, which can obtain a structure having no unevenness in fatigue strength even if mechanical properties are classified.
【０００６】[0006]
【課題を解決するための手段】上記課題を解決するため
の請求項１に記載の発明は、 鉄基合金材料に材料表面
が溶融しない条件下に１回乃至２０回のレーザ照射によ
る急速加熱および急速冷却を施すことを要旨とする。According to a first aspect of the present invention, there is provided a method for rapidly heating a ferrous alloy material by laser irradiation once to 20 times under conditions that the material surface does not melt. The point is to provide rapid cooling.
【０００７】請求項２に記載の発明は、疲労による損傷
を受けた鉄基合金材料の該疲労損傷部にレーザビームを
照射して溶融・凝固せしめた後、該溶融・凝固部および
その幾何学的形状急変部近傍に、材料表面が溶融しない
条件下に１回乃至２０回のレーザ照射による急速加熱お
よび急速冷却を施すことを特徴とするレーザ照射による
金属組織の微細化方法である。[0007] The invention according to claim 2 is to provide a method for irradiating a laser beam on the fatigue-damaged portion of an iron-based alloy material damaged by fatigue to cause it to melt and solidify, and then form the molten-solidified portion and its geometry. A method for refining a metal structure by laser irradiation, characterized in that rapid heating and rapid cooling by laser irradiation once to 20 times are performed in the vicinity of a rapidly changing portion of the material under conditions that the material surface does not melt.
【０００８】請求項３に記載の発明は、鉄基合金材料に
材料表面が溶融しない条件下になされる１回乃至２０回
のレーザ照射が、レーザビームの焦点を材料表面から所
定寸法だけ離隔せしめた焦点外し距離の存在下になされ
るものである請求項１または請求項２に記載のレーザ照
射による金属組織の微細化方法である。According to a third aspect of the present invention, the laser irradiation is performed once to 20 times under the condition that the material surface does not melt in the iron-based alloy material, and the focal point of the laser beam is separated from the material surface by a predetermined dimension. 3. The method according to claim 1, wherein the metallographic structure is refined by laser irradiation.
【０００９】請求項４に記載の発明は、レーザ照射用ト
ーチを担持するロボットと、該ロボットの移動方向およ
び移動速度制御機構と、レーザ照射位置における温度の
モニタリング装置と、レーザビームの焦点外し距離制御
機構とを有してなるレーザ照射による金属組織の微細化
装置である。According to a fourth aspect of the present invention, there is provided a robot carrying a torch for laser irradiation, a moving direction and moving speed control mechanism of the robot, a temperature monitoring device at a laser irradiation position, and a defocus distance of a laser beam. This is an apparatus for refining a metal structure by laser irradiation having a control mechanism.
【００１０】[0010]
【作用】本発明は叙上の構成になるから、鉄基合金の溶
接接合部等所望の部位の結晶組織を数μｍオーダーまで
微細化することができ、近年の著しく高抗張力化された
鉄基合金の特性を十分に活かすことができる。また、所
望の部位の金属組織を微細化し強化することができる。Since the present invention has the above-described structure, the crystal structure of a desired portion such as a welded joint of an iron-based alloy can be refined to the order of several μm. The properties of the alloy can be fully utilized. Further, the metal structure at a desired portion can be refined and strengthened.
【００１１】[0011]
【発明の実施の形態】以下、本発明をその好ましい実施
形態に則して説明する。DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on preferred embodiments.
【００１２】本発明においては、低炭素鋼といった鉄基
合金における所望の部位、たとえば溶接継手部の溶接金
属および母材熱影響部に対し、１回乃至２０回の、レー
ザ照射による急速加熱および急速冷却を施すことがポイ
ントの１つである。図１に、厚さ：６ｍｍの軟鋼板（重
量で、Ｃ：０．１％、Ｓｉ：０．１５％、Ｍｎ：０．５
２％、Ｐ：０．０２％、Ｓ：０．０２％、残部：Ｆｅお
よび不可避的不純物、結晶粒径：２３μｍ）について、
溶接継手部にレーザ照射を行ったときの、レーザ照射回
数と、フェライト結晶粒径ｄの関係を示す。このとき用
いたレーザはＹＡＧレーザ加工機であり、レーザ出力
Ｐ：１．５ＫＷ、照射速度ｖ：０．５ｍ／分、焦点外し
距離Ｆｄ：４０ｍｍ、シールドガス：Ａｒガス（流量：
３０ｌ／分）の条件でレーザ照射を行ったものである。In the present invention, a desired portion in an iron-based alloy such as a low carbon steel, for example, a weld metal and a base material heat-affected zone of a welded joint portion is heated and rapidly heated once to 20 times by laser irradiation. Cooling is one of the points. FIG. 1 shows a mild steel plate having a thickness of 6 mm (by weight, C: 0.1%, Si: 0.15%, Mn: 0.5
2%, P: 0.02%, S: 0.02%, balance: Fe and unavoidable impurities, crystal grain size: 23 μm)
The relationship between the number of laser irradiations and the ferrite grain size d when laser irradiation is performed on the weld joint is shown. The laser used at this time was a YAG laser processing machine, with a laser output P of 1.5 KW, an irradiation speed v of 0.5 m / min, a defocus distance Fd of 40 mm, and a shielding gas of Ar gas (flow rate:
(30 l / min).
【００１３】図１から明らかなように、溶接金属（Ｗ．
Ｍ．）下面（溶融境界部）から０ｍｍ、０．１ｍｍ、
０．２ｍｍの位置におけるフェライト粒径ｄは、レーザ
照射回数の増加に対応して小さくなっている。レーザ照
射を１回行うと、結晶粒径は約６μｍと初期の結晶粒径
の約１／４の大きさとなっている。さらに、レーザ照射
を繰り返すと、レーザ照射回数の増加に対応して結晶粒
径は次第に小さくなる。５回〜 ６回以上になる
とほぼ４μｍと一定の大きさに収束する。この最終的な
粒径は、鋼板の化学的組成、レーザ出力、レーザトーチ
の移動速度、焦点外し距離Ｆｄによって異なるが、何れ
の条件においても、レーザ照射を最大で２０回まで繰り
返すことによって、ほぼ一定の粒径の微細粒に到達す
る。As is apparent from FIG. 1, the weld metal (W.
M. ) 0 mm, 0.1 mm from the lower surface (melt boundary),
The ferrite grain size d at the position of 0.2 mm decreases with an increase in the number of laser irradiations. When laser irradiation is performed once, the crystal grain size is about 6 μm, which is about １ ／ of the initial crystal grain size. Further, when laser irradiation is repeated, the crystal grain size gradually decreases in accordance with the increase in the number of laser irradiations. When the number of times is 5 to 6 or more, it converges to a constant size of about 4 μm. The final particle size varies depending on the chemical composition of the steel sheet, the laser output, the moving speed of the laser torch, and the defocus distance Fd, but under any condition, the laser irradiation is repeated up to 20 times, and is almost constant. Fine particles having a particle size of
【００１４】低炭素鋼といった鉄鋼材料は、γ―α変態
によってフェライト粒が微細化する。従来の焼ならし処
理はこの変態を利用するものであるが、加熱速度および
冷却速度が低いために、到達し得る粒径が２０μｍ〜３
０μｍと結晶粒の微細化には限界があった。発明者ら
は、加熱速度および冷却速度をきわめて高くとれるレー
ザビームを用いれば結晶粒の微細化を格段に進め得るも
のと考え、ＹＡＧレーザ加工機を用いて鉄鋼材料表面に
レーザ照射を施して結晶粒の微細化を試みた。In a steel material such as a low carbon steel, ferrite grains are refined by γ-α transformation. The conventional normalizing process utilizes this transformation. However, since the heating rate and the cooling rate are low, the particle size that can be reached is 20 μm to 3 μm.
There was a limit to the grain refinement of 0 μm. The present inventors believe that the use of a laser beam capable of extremely high heating and cooling rates can significantly advance the refinement of crystal grains. We tried to refine the grains.
【００１５】その結果、母材のフェライト粒径：２３μ
ｍであったものが、１回のレーザ照射による急速加熱、
急速冷却によって、６μｍとなった。レーザ照射を繰り
返すことによってフェライト粒はさらに微細化して行
き、５回以上のレーザ照射で４μｍとなった。また、溶
接部における結晶粒は、母材に比較するとさらに大きく
なっているが、これも２回のレーザ照射によって４μｍ
以下に微細化された。As a result, the ferrite particle diameter of the base material: 23 μm
m, rapid heating by one laser irradiation,
It became 6 μm by rapid cooling. By repeating the laser irradiation, the ferrite grains were further refined and became 4 μm by five or more laser irradiations. The crystal grain size in the weld is larger than that of the base metal, but this is also 4 μm by two laser irradiations.
It was miniaturized below.
【００１６】通常の焼ならし処理の場合の鉄鋼材料の加
熱速度および冷却速度は、何れも０．１℃／ｓであるの
に対し、鋼板の表面にレーザ照射を行ったときの加熱速
度は約３００℃／ｓ以上（５００℃〜８００℃における
平均加熱速度）通常約８００℃／ｓ程度であり、冷却速
度は約１０℃／ｓ〜４００℃／ｓ（８００℃〜５００℃
における平均冷却速度）である。このように、レーザ照
射によるときの加熱速度および冷却速度は、焼きならし
処理における加熱速度および冷却速度の１００倍―８０
００倍である。このことが、α―γ変態によって生じる
γ（オーステナイト）粒の成長を抑制し、引き続く冷却
過程におけるγ―α変態によるα粒の成長も抑制するこ
とになる。また、加熱速度がきわめて高いために、１回
のレーザ照射では材料全体の組織がγ（オーステナイ
ト）化されることはなく、材料全体をγ（オーステナイ
ト）化するにはレーザ照射の繰り返しが必要となるが、
レーザ照射回数が増大するにつれて微細フェライト粒界
の総長さが増大するために、次のレーザ照射によるγ
（オーステナイト）化のための核生成サイトが増加す
る。そして、γ粒も微細化され、その後の冷却過程にお
けるα粒の核生成サイトも増加する。その結果、フェラ
イト核は成長できずに微細粒になるのである。The heating rate and the cooling rate of the steel material in the normal normalizing process are both 0.1 ° C./s, whereas the heating rate when the surface of the steel sheet is irradiated with the laser is 300 ° C./s or more (average heating rate at 500 ° C. to 800 ° C.) Usually about 800 ° C./s, and cooling rate is about 10 ° C./s to 400 ° C./s (800 ° C. to 500 ° C.)
Average cooling rate). Thus, the heating rate and the cooling rate by the laser irradiation are 100-80 times the heating rate and the cooling rate in the normalizing process.
It is 00 times. This suppresses the growth of γ (austenite) grains generated by the α-γ transformation, and also suppresses the growth of α grains by the γ-α transformation in the subsequent cooling process. In addition, since the heating rate is extremely high, the structure of the entire material is not converted to γ (austenite) by one laser irradiation, and it is necessary to repeat the laser irradiation to convert the entire material to γ (austenite). But
Since the total length of the fine ferrite grain boundaries increases as the number of laser irradiations increases,
The number of nucleation sites for (austenite) formation increases. The γ grains are also refined, and the number of nucleation sites for α grains in the subsequent cooling process is increased. As a result, ferrite nuclei cannot be grown and become fine grains.
【００１７】次に、焦点外し距離について説明する。図
２に、レーザビーム焦点外し距離（レーザビームの焦点
と照射対象表面間の距離）Ｆｄ（ｍｍ）と、微細化結晶
領域の深さの関係を示す。図３に、レーザビームの焦点
外し距離Ｆｄ（ｍｍ）と、微細化結晶領域の幅の関係を
示す。図２および図３何れも鋼板の厚さ６ｍｍのときの
ものである。図２および図３から明らかなように、材料
表面が溶融しない条件下で、レーザビームの焦点外し距
離Ｆｄが４７ｍｍのときに最大の深さおよび幅が得られ
ている。このように、レーザビームの焦点外し距離Ｆｄ
は、結晶粒の微細化プロセスの制御における重要な操作
パラメータである。Next, the defocus distance will be described. FIG. 2 shows the relationship between the defocus distance of the laser beam (the distance between the focal point of the laser beam and the surface to be irradiated) Fd (mm) and the depth of the miniaturized crystal region. FIG. 3 shows the relationship between the defocus distance Fd (mm) of the laser beam and the width of the miniaturized crystal region. Both FIG. 2 and FIG. 3 show the case where the thickness of the steel plate is 6 mm. As is clear from FIGS. 2 and 3, the maximum depth and width are obtained when the defocus distance Fd of the laser beam is 47 mm under the condition that the material surface does not melt. Thus, the defocus distance Fd of the laser beam
Is an important operating parameter in controlling the grain refinement process.
【００１８】本発明のレーザ照射による金属組織の微細
化方法は、鉄鋼材料の疲労による亀裂等の損傷に対し
て、その損傷箇所をレーザビーム照射によって溶融・凝
固させ、その部分に適用することによって、機械的特性
を回復させることができる。The method for refining a metal structure by laser irradiation according to the present invention is characterized in that, for damage such as a crack due to fatigue of a steel material, the damaged portion is melted and solidified by laser beam irradiation and applied to the portion. , Can restore the mechanical properties.
【００１９】次に、本発明のレーザ照射による金属組織
の微細化方法を実施するときに用いる装置について、説
明する。図４に、本発明のレーザ照射による金属組織の
微細化装置の概略を示す。図４において、１はレーザ発
振器、２は光ケーブル、３はレーザトーチ、である。４
はレーザビームであって、Ｆｄが焦点外し距離である。
５は鋼板であり、レーザ照射対象である。６はレーザト
ーチ操作ロボット制御機構である。このレーザトーチ操
作ロボット制御機構６によって、ロボットの進行方向お
よび進行速度が制御される。７は焦点外し距離Ｆｄ制御
機構であって、鋼板５の表面位置（高さ）やレーザトー
チ位置を操作パラメータとして、焦点外し距離Ｆｄを制
御する。レーザ発振器１から出たレーザビーム４は、光
ケーブル２によって導出され、レーザトーチ３により鋼
板５の表面に照射される。レーザ照射は、鋼板の結晶粒
径が所望の大きさに微細化されるまで繰り返される。鋼
板５が疲労を受けていない場合は、レーザ照射部が溶融
しない条件下にレーザ照射を行う。疲労に起因する亀裂
等の損傷を受けている場合は、その領域をレーザビーム
照射によって溶融・凝固させた後、再溶融しない条件下
にレーザ照射を繰り返して表面部の結晶を微細化させ
る。Next, a description will be given of an apparatus used when performing the method for refining a metal structure by laser irradiation according to the present invention. FIG. 4 schematically shows an apparatus for refining a metal structure by laser irradiation according to the present invention. In FIG. 4, 1 is a laser oscillator, 2 is an optical cable, and 3 is a laser torch. 4
Is a laser beam, and Fd is a defocus distance.
Reference numeral 5 denotes a steel plate, which is a laser irradiation target. Reference numeral 6 denotes a laser torch operation robot control mechanism. The laser torch operation robot control mechanism 6 controls the traveling direction and traveling speed of the robot. Reference numeral 7 denotes a defocus distance Fd control mechanism that controls the defocus distance Fd using the surface position (height) of the steel plate 5 and the laser torch position as operation parameters. The laser beam 4 emitted from the laser oscillator 1 is led out by the optical cable 2 and irradiated on the surface of the steel plate 5 by the laser torch 3. Laser irradiation is repeated until the crystal grain size of the steel sheet is reduced to a desired size. When the steel sheet 5 is not fatigued, laser irradiation is performed under the condition that the laser irradiation part does not melt. If the area is damaged by cracks or the like due to fatigue, the area is melted and solidified by laser beam irradiation, and then the laser irradiation is repeated under conditions that do not cause re-melting to refine the crystal on the surface.
【００２０】[0020]
【実施例】重量で、Ｃ：０．１％、Ｓｉ：０．１５％、
Ｍｎ：０．５２％、Ｐ：０．０２％、Ｓ：０．０２％、
残部：Ｆｅおよび不可避的不純物からなる低炭素鋼の厚
さ：３ｍｍ、４ｍｍ、５ｍｍおよび６ｍｍの鋼板を、５
０ｍｍ×５０ｍｍに切断し、ＹＡＧレーザ加工機をを用
いて、出力Ｐ：１．５ＫＷ、照射速度ｖ：０．５ｍ／
分、焦点外し距離Ｆｄ：４０ｍｍ、シールドガス：Ａｒ
ガス（流量：３０ｌ／分）の条件の下で試験片中央部に
長さ：１００ｍｍのレーザ照射を繰り返し行った。この
レーザ照射によって溶融・凝固した領域は、鋼板表面か
ら深さ：０．２ｍｍであった。冷却速度を一定するため
に、試験片が室温まで降温した後に次のレーザ照射を行
った。レーザ照射回数は、最大で１０回までとした。EXAMPLE C: 0.1%, Si: 0.15% by weight,
Mn: 0.52%, P: 0.02%, S: 0.02%,
The balance: Low carbon steel composed of Fe and inevitable impurities Thickness: 3 mm, 4 mm, 5 mm and 6 mm steel plates
It was cut into 0 mm x 50 mm, and using a YAG laser beam machine, output P: 1.5 KW, irradiation speed v: 0.5 m /
Min, defocus distance Fd: 40 mm, shielding gas: Ar
Under the condition of gas (flow rate: 30 l / min), laser irradiation with a length of 100 mm was repeatedly applied to the center of the test piece. The region melted and solidified by the laser irradiation had a depth of 0.2 mm from the surface of the steel sheet. In order to make the cooling rate constant, the next laser irradiation was performed after the test piece was cooled to room temperature. The number of laser irradiations was up to 10 times.
【００２１】厚さ：３ｍｍ、４ｍｍ、５ｍｍおよび６ｍ
ｍの鋼板について、レーザ照射部の熱サイクルの実測を
行った。測定位置における最高加熱温度は、９３０℃〜
９８０℃であった。５００℃〜８００℃における平均昇
温速度は８００℃／ｓで、板厚によっては殆ど変化しな
かった。冷却速度は、板厚が３ｍｍのときに１２０℃／
ｓであり、板厚が大きくなるに従って冷却速度が高くな
り、板厚が６ｍｍの場合は４４０℃／ｓであった。何れ
にしても、レーザ照射による加熱・冷却挙動は急速加
熱、急速冷却であることが分かった。Thickness: 3 mm, 4 mm, 5 mm and 6 m
For the steel plate of m, the actual measurement of the thermal cycle of the laser irradiation part was performed. The maximum heating temperature at the measurement position is 930 ° C
980 ° C. The average heating rate at 500 ° C. to 800 ° C. was 800 ° C./s, and hardly changed depending on the plate thickness. The cooling rate is 120 ° C. /
s, and the cooling rate increased as the plate thickness increased, and was 440 ° C./s when the plate thickness was 6 mm. In any case, the heating / cooling behavior by laser irradiation was found to be rapid heating and rapid cooling.
【００２２】板厚：６ｍｍの鋼板について、レーザ照射
前の組織ならびにレーザ照射回数１回および１０回のと
きの結晶組織を図５に示す。レーザ照射前のフェライト
粒径は２３μｍであって、レーザ照射回数が１回の場合
は、フェライト粒径はレーザ照射前の粒径に比し小さく
なっているけれども、結晶粒の大きさにばらつきが見ら
れる。また、元々パーライトであった部分が焼入れ組織
に変化している。照射回数が１０回の場合は、結晶粒は
さらに細かくなり、レーザ照射１回の場合に見られた焼
き入れ組織は殆ど見られない。FIG. 5 shows the structure of a steel plate having a thickness of 6 mm before laser irradiation and the crystal structures when the laser irradiation was performed once and ten times. The ferrite particle size before laser irradiation is 23 μm, and when the number of laser irradiations is one, the ferrite particle size is smaller than the particle size before laser irradiation, but the crystal grain size varies. Can be seen. In addition, the part originally being pearlite has changed to a quenched structure. When the number of irradiations is 10, the crystal grains become finer, and the hardened structure observed in the case of one laser irradiation is hardly observed.
【００２３】切片法を用いて、ボンド部から各深さ毎の
フェライトの大きさを測定した。板厚が６ｍｍの場合の
結果を、図６に示す。図６における△、○、●は、ボン
ド部からの距離（深さ）が０ｍｍ、０．１ｍｍ及び０．
２ｍｍの位置における結晶粒の大きさを示す。レーザ照
射前の結晶粒径は、２３μｍであった。Using the intercept method, the size of the ferrite at each depth from the bond was measured. FIG. 6 shows the results when the plate thickness is 6 mm. 6, .largecircle., .Largecircle., And .circle-solid. Represent distances (depths) from the bond portions of 0 mm, 0.1 mm, and 0.
The size of a crystal grain at a position of 2 mm is shown. The crystal grain size before laser irradiation was 23 μm.
【００２４】何れの位置においても、レーザ照射回数が
増すと、結晶粒径は次第に小さくなっている。ボンド部
からの深さが０．２ｍｍの位置において、４回目のレー
ザ照射で結晶粒径は約４μｍ程になった。また、△（０
ｍｍ）のようにボンド部近傍では高温に加熱されるの
で、深さが０．１ｍｍ〜０．２ｍｍの部分に比し、結晶
粒は少し大きくなった。At any position, as the number of laser irradiation increases, the crystal grain size gradually decreases. At a position at a depth of 0.2 mm from the bond portion, the fourth laser irradiation reduced the crystal grain size to about 4 μm. Also, △ (0
mm), the vicinity of the bond portion is heated to a high temperature, so that the crystal grains are slightly larger than the portion having a depth of 0.1 mm to 0.2 mm.
【００２５】同様に、板厚が３ｍｍ、４ｍｍおよび５ｍ
ｍの場合の結晶粒の大きさを測定した。図７に、ボンド
部からの距離が０．２ｍｍの位置における板厚と結晶粒
の大きさを、レーザ照射回数をパラメータとして示す。
図７から明らかなように、レーザ照射１回の場合、結晶
粒の大きさは板厚間で大きな差違は認められなかった。
３回目のレーザ照射では、結晶粒の大きさは板厚：６ｍ
ｍ場合に４．３μｍであったのに対し、板厚：３ｍｍの
場合には５．２μｍと大きかった。これは、板厚が小さ
いほど冷却速度が低くなり、それに伴って結晶粒の微細
化効果が小さくなったものと考えられる。しかし、レー
ザ照射を７回、９回と繰り返すと、結晶粒の大きさに板
厚による差違はあまり見られなくなった。Similarly, when the plate thickness is 3 mm, 4 mm and 5 m
The crystal grain size in the case of m was measured. FIG. 7 shows the plate thickness and the size of crystal grains at a position at a distance of 0.2 mm from the bond portion, using the number of laser irradiations as a parameter.
As is clear from FIG. 7, in the case of one laser irradiation, no large difference in crystal grain size was observed between the plate thicknesses.
In the third laser irradiation, the crystal grain size is 6 m
In the case of m, the thickness was 4.3 μm, whereas in the case of the plate thickness: 3 mm, it was as large as 5.2 μm. This is presumably because the cooling rate was lower as the plate thickness was smaller, and the crystal grain refining effect was reduced accordingly. However, when the laser irradiation was repeated seven times and nine times, the difference in the size of the crystal grains due to the plate thickness was not much observed.
【００２６】レーザ照射を繰り返すと結晶粒は次第に微
細化し、母材の結晶粒径：２３μｍに対して、板厚：６
ｍｍの場合、４回目のレーザ照射で約４μｍ程となっ
た。また、板厚が小さくなると結晶粒の微細化効果は若
干低下するが、レーザ照射７回以上になると、約４．３
μｍの一定値となった。When the laser irradiation is repeated, the crystal grains are gradually refined, and the thickness of the base material is 6 μm while the crystal grain size of the base material is 23 μm.
mm, it was about 4 μm in the fourth laser irradiation. In addition, the effect of crystal grain refinement is slightly reduced as the plate thickness is reduced.
It became a constant value of μm.
【００２７】[0027]
【発明の効果】本発明によれば、鉄基合金の溶接継手部
等所望の局部的領域の結晶組織を数μｍオーダにまで微
細化することができ、疲労強度を高くすることができる
とともに、鉄鋼材料の高抗張力化等特性改良技術の成果
を十分に活かすことができる。According to the present invention, the crystal structure of a desired local region such as a weld joint of an iron-based alloy can be refined to the order of several μm, and the fatigue strength can be increased. The results of technology for improving properties such as high tensile strength of steel materials can be fully utilized.
【００２８】請求項２に記載の発明によれば、疲労に起
因する亀裂等の局部的損傷箇所も、これを再溶融して亀
裂をなくすだけでなく、転位密度を減少させて新生化し
た後、焦点外し距離を制御されるレーザビーム照射によ
って溶融・凝固せしめた後、組織を微細化し、完全に回
復させることができる。また、幾何学的形状の急変部の
表面部のみの組織を微細化し、以て疲労強度を建設時よ
りも高くすることができる。According to the second aspect of the present invention, a locally damaged portion such as a crack due to fatigue is not only re-melted to eliminate the crack, but also after the dislocation density is reduced and regenerated. After being melted and solidified by laser beam irradiation whose defocus distance is controlled, the tissue can be refined and completely recovered. Further, the structure of only the surface portion of the suddenly changing portion of the geometrical shape can be made finer, so that the fatigue strength can be made higher than at the time of construction.
【００２９】請求項３に記載の発明によれば、鉄基合金
の組織微細化領域の深さや幅ならびに材料への入熱量を
容易に制御できる。According to the third aspect of the present invention, it is possible to easily control the depth and width of the microstructured region of the iron-based alloy and the amount of heat input to the material.
【００３０】請求項４に記載の発明によれば、簡潔な装
置構成にしてレーザビーム照射部位の温度を、冶金学的
に最も好ましい領域に維持しながら溶接継手部等の組織
の微細化を遂行できる。According to the fourth aspect of the present invention, the structure of the welded joint and the like is refined while maintaining the temperature of the laser beam irradiation site in the most preferable region from the viewpoint of metallurgy by using a simple apparatus configuration. it can.
【図１】レーザ照射繰り返し回数とフェライト粒径の関
係を示すグラフFIG. 1 is a graph showing the relationship between the number of laser irradiation repetitions and the ferrite particle size
【図２】レーザビームの焦点外し距離Ｆｄと結晶微細化
領域の深さの関係を示すグラフFIG. 2 is a graph showing a relationship between a defocus distance Fd of a laser beam and a depth of a crystal refinement region.
【図３】レーザビームの焦点外し距離Ｆｄと結晶微細化
領域の幅の関係を示すグラフFIG. 3 is a graph showing a relationship between a defocus distance Fd of a laser beam and a width of a crystal refinement region.
【図４】本発明のレーザ照射による金属組織の微細化装
置を示す略図FIG. 4 is a schematic view showing an apparatus for refining a metal structure by laser irradiation according to the present invention.
【図５】板厚：６ｍｍの鋼板について、レーザ照射繰り
返し回数１回および１０回のときの結晶組織を示す写真FIG. 5 is a photograph showing a crystal structure of a steel plate having a thickness of 6 mm when laser irradiation is repeated once and ten times.
【図６】本発明の位置実施例におけるレーザ照射繰り返
し回数と、溶融境界部からの距離（深さ）毎のフェライ
ト粒径ｄとの関係を示すグラフFIG. 6 is a graph showing the relationship between the number of repetitions of laser irradiation and the ferrite grain size d for each distance (depth) from a fusion boundary in a position example of the present invention.
【図７】鋼板の厚さとフェライト粒径ｄとの関係を、レ
ーザ照射繰り返し回数をパラメータとして示すグラフFIG. 7 is a graph showing the relationship between the thickness of a steel sheet and the ferrite grain size d using the number of laser irradiation repetitions as a parameter.
【符号の説明】 １ レーザ発振器 ２ 光ケーブル ３ レーザトーチ ４ レーザビーム ５ 鋼板 ６ レーザトーチ操作ロボット制御機構 ７ 焦点外し距離Ｆｄ制御機構[Description of Signs] 1 Laser oscillator 2 Optical cable 3 Laser torch 4 Laser beam 5 Steel plate 6 Laser torch operation robot control mechanism 7 Defocus distance Fd control mechanism
Claims (4)
件下に１回乃至２０回のレーザ照射による急速加熱およ
び急速冷却を施すことを特徴とするレーザ照射による金
属組織の微細化方法。1. A method for refining a metal structure by laser irradiation, wherein the iron-based alloy material is subjected to rapid heating and rapid cooling by laser irradiation once to 20 times under the condition that the material surface is not melted.
該疲労損傷部にレーザビームを照射して溶融・凝固せし
めた後、該溶融・凝固部およびその幾何学的形状急変部
近傍に、材料表面が溶融しない条件下に１回乃至２０回
のレーザ照射による急速加熱および急速冷却を施すこと
を特徴とするレーザ照射による金属組織の微細化方法。2. A laser beam is applied to the fatigue-damaged portion of the iron-based alloy material damaged by fatigue to cause the iron-based alloy material to melt and solidify. A method for refining a metal structure by laser irradiation, wherein rapid heating and rapid cooling by laser irradiation are performed once to 20 times under a condition that the material surface is not melted.
件下になされる１回乃至２０回のレーザ照射が、レーザ
ビームの焦点を材料表面から所定寸法だけ離隔せしめた
焦点外し距離の存在下になされるものである請求項１ま
たは請求項２に記載のレーザ照射による金属組織の微細
化方法。3. The method of claim 1, wherein the laser irradiation is performed once to 20 times under a condition that the material surface does not melt in the iron-based alloy material, in the presence of an out-of-focus distance that separates a focal point of the laser beam from the material surface by a predetermined dimension. 3. The method for refining a metal structure by laser irradiation according to claim 1 or claim 2.
と、該ロボットの移動方向および移動速度制御機構と、
レーザ照射位置における温度のモニタリング装置と、レ
ーザビームの焦点外し距離制御機構とを有してなるレー
ザ照射による金属組織の微細化装置。4. A robot carrying a torch for laser irradiation, a moving direction and moving speed control mechanism of the robot,
An apparatus for refining a metal structure by laser irradiation, comprising: a temperature monitoring device at a laser irradiation position; and a laser beam defocus distance control mechanism.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001058489A JP4953172B2 (en) | 2001-03-02 | 2001-03-02 | Method to refine ferrite structure by laser irradiation |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001058489A JP4953172B2 (en) | 2001-03-02 | 2001-03-02 | Method to refine ferrite structure by laser irradiation |
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| Country | Link |
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| JP2013087351A (en) * | 2011-10-21 | 2013-05-13 | Toyota Central R&D Labs Inc | Nitride metal member and method for manufacturing the same |
| JP2014133940A (en) * | 2013-01-11 | 2014-07-24 | Toyota Central R&D Labs Inc | Metal member and production method thereof |
| WO2020003950A1 (en) | 2018-06-27 | 2020-01-02 | Smc株式会社 | Butt welded joint of steel material and method for manufacturing same |
| CN111693563A (en) * | 2020-05-08 | 2020-09-22 | 新兴际华集团有限公司 | Method for analyzing structure and performance of iron-based remelted layer |
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| Publication number | Publication date |
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| JP4953172B2 (en) | 2012-06-13 |
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