【発明の詳細な説明】[Detailed description of the invention]
本発明はガスシールドアーク溶接用ソリツドワ
イヤに関し、殊にアーク点までの送給性が良好で
且つ溶滴移行性の優れた同ワイヤに関するもので
ある。
本発明のガスシールドアーク溶接用ソリツドワ
イヤ（以下単にワイヤと言う）は、軟鋼の溶接だ
けでなく50キロ級或は更に60キロ級以上の高張力
鋼、又はCr−Mo鋼等の合金鋼の溶接にも広く適
用し得るもので、CO2、Ar−CO2、Ar−O2、
CO2−O2、Ar−CO2−O2、Ar、He等種々のシー
ルドガスと組合せて使用される。
この種のワイヤを用いてシールドガスアーク溶
接を行なうに当たつては、ワイヤを送給ローラに
よつてコンジツトチユーブ内へ送り込み、通電チ
ツプとの接触によつて通電しつつ母材との間でア
ークを発生させて溶接を行なうが、アークを安定
に保ち良好な溶接作業性を確保するうえでワイヤ
の送給性は極めて重要となる。また如何に送給性
が良好であつても、ワイヤ先端から母材方向への
溶滴移行性が良好でなければ安定なアークは得ら
れない。
この様なところから、ワイヤの送給性及び溶滴
移行性の改善を期して種々の研究が行なわれてい
るが、何れも現場の要求を満たすものとは言えな
い。例えば特開昭58−128294号公報は、特にワイ
ヤの送給性を改善することを目的とするもので、
素ワイヤの表層酸素濃度を50〜400ppmとするこ
とによつて素ワイヤ表面に微小亀裂を生ぜしめた
後、銅めつきを施し、銅めつきワイヤの表面に前
記微小亀裂に対応する亀裂を発生させ、この亀裂
に含油させることによつて表面滑性を高めようと
している。しかしながらこの発明は前述の如く送
給性だけに注目したもので、溶滴移行性について
は格別の考慮が払われていない為、アーク安定性
という総合的観点から見た場合、不十分と言わざ
るを得ない。一方ワイヤ表面付近の酸素濃度を80
〜1000ppm程度まで高め、溶鋼の表面張力を低下
させることによつて溶滴移行性を高める技術も知
られているが、この場合は溶滴移行性のみが注目
されワイヤ送給性に格別の考慮が払われていない
為、やはりアーク安定性は不十分である。
この様にこれまでの技術では、ワイヤ送給性と
溶滴移行性を夫々個別に改善してアーク安定性を
高めようとしているのであり、両性能を同時に高
めそれらの相乗的効果によりアーク安定性を改善
しようとする試みは提案されていない様である。
本発明者等はこうした状況に鑑み、ワイヤ送給
性と溶滴移行性と共に高めてやれば、アーク安定
性を少なくとも相加的に、場合によつては相乗的
に改善することができるのではないかと考え、従
来技術を更に深く掘り下げて研究を進めてきた。
その結果、素ワイヤ表層部の酸素濃度をある値以
上に高めてやれば、酸素の存在により溶滴移行性
が改善されると共に表面に無数の微小亀裂が発生
して、潤滑剤の保留能が向上してワイヤ送給性が
改善され、アーク安定性を大幅に高め得ることが
確認された。まためつき処理を行なう場合でもめ
つき層表面にも前記微小亀裂に対応する亀裂がで
き同様の効果が得られることが確認された。
本発明はかかる確認結果を基に更に実験を重ね
て完成されたものであつて、その構成は、素ワイ
ヤ表層部を酸化することによつて酸化物を形成す
ると共に素ワイヤ周表面から該素ワイヤの直径に
対して2.5％までの表層部における酸素濃度が
1100ppm以上であり、且つ表層に多数の微小亀裂
を形成したところに要旨を有するものである。
本発明のワイヤは、コンジツトチユーブ内での
摩擦抵抗を減少して送給性を高める為に、素ワイ
ヤ表面の酸素濃度を1100ppm以上に高めて素ワイ
ヤ表面、またはめつきワイヤ表面に無数の微小亀
裂を形成することにより表面滑性を高めることに
よつて送給抵抗を低減すると共に、適量の酸化物
の存在によつて溶滴の表面張力を低下させること
により溶滴移行性を高めるもので、この様なワイ
ヤは、伸線、めつき前のワイヤ（素ワイヤ）を熱
処理（焼鈍）することにより粒界酸化層を生成さ
せた後、該粒界酸化層を残存させたままで伸線お
よび伸線した後めつき処理を行なうこと、まため
つき処理した後、伸線することによつて容易に得
ることができる。即ち表層酸素濃度が1100ppm以
上となる程度の粒界酸化層を形成させた後伸線す
ると、前述の如く表面に無数の微小亀裂が発生す
る。また該素ワイヤの表面にめつきを施すと、上
記微小亀裂の形成面に沿つてめつき層が形成され
る為、表面に無数の亀裂を有するめつきワイヤと
なる。なお、粒界酸化層を形成させた後、めつき
処理し伸線することによつても素ワイヤに亀裂が
発生する時に同時にめつき層にも亀裂が出来るの
で、ワイヤ表面に無数の微小亀裂を有するワイヤ
を得ることが出来る。ところで、ワイヤ表面に送
給性を十分に高めることのできる亀裂を形成させ
る為には、ワイヤ表層部の酸素濃度を800ppm以
上にすればよいことが確認された。しかし同時に
溶滴の離脱性を有効に高める為には上記表層酸素
濃度では不十分であり、後記実験例でも明らかに
する如く該酸素濃度を1100ppm以上にすべきであ
ることが判明した。但し粒界酸化層の形成によつ
て表層酸素濃度を高める方法では、該酸素濃度を
高めすぎると粒界酸化層が厚くなりすぎてめつき
の密着性が悪化し、ワイヤ送給時にめつき層が剥
離してコンジツトチユーブ内にめつき屑が詰ま
り、ワイヤ送給性がかえつて低下することがあ
る。従つてこうした問題を回避する為には表層酸
素濃度を8000ppm程度以下に抑えるのがよく、結
局本発明における最も好ましい表層酸素濃度は
1100〜8000ppmの範囲となる。
尚本発明で酸素濃度が規定される素ワイヤの表
層とは、素ワイヤ周表面から該素ワイヤ直径の
2.5％までの表層部を言い、該表層酸素濃度ｚ
（ppm）は、ワイヤ全体の酸素濃度をｘ（ppm）、
素ワイヤ表面を前記2.5％以上の深さまで研削除
去した後の残部ワイヤの酸素濃度（ワイヤ中心部
の酸素濃度）をｙ（ppm）とし、素ワイヤ直径の
2.5％までの表層部を除いたワイヤ中心部の酸素
濃度もｙ（ppm）に等しいと仮定して簡易的に次
式から求めることができる。
｛π（Ｄ／２）2−π（Ｄ−５／100Ｄ／２）2｝ｚ
＝π（Ｄ／２）2x−π（Ｄ−５／100Ｄ／２）2y
上記式より次の次式が導びかれ、
π／２・ｚ｛D2−（Ｄ−５／100Ｄ）2｝
＝π／４・D2・ｘ−π／４（Ｄ−５／100Ｄ）2・ｙ
この式を更に整理すると
ｚ・D2｛１−（95／100）2｝
＝D2・ｘ−D2・（95／100）2・ｙ
この式を更に整理して変形すると
ｚ≒10.3x−9.3y
が導びかれ、結局ワイヤ全体の酸素濃度(x)とワイ
ヤ中心部（表層部を除く）の酸素濃度(y)から表層
部の酸素濃度(z)を求めることができる。
尚表層酸素濃度を高める方法としては、原線表
面に生成している粒界酸化層の除去量を調整して
残存酸化物量をコントロールした後伸線加工を行
なうか、或は原線表面の酸化物皮膜を一旦完全に
除去した後再度表面酸化を行ない酸化物皮膜を形
成した後伸線加工を行なう方法が最も一般的であ
る。
本発明は以上の様に構成されるが、要は素ワイ
ヤ表面に粒界酸化層を形成してその表層酸素濃度
を1100ppm以上にすることによつて、めつきワイ
ヤの表面に適度の微小亀裂を形成することがで
き、それにより潤滑油の保持能力を向上させてワ
イヤの表面潤滑性を高め送給性を改善すると共
に、表層酸素の存在によつて溶滴移行性を高める
ことができ、これら両者の効果が相まつてアーク
安定性を大幅に改善し得ることになつた。その結
果、溶接時のスパツタ発生量が激減すると共にビ
ード形状や外観の改善され、更にはCO2溶接にお
いては短絡回数が増加して溶接作業性が良好とな
り、（Ar−CO2）を使用するMAG溶接において
はスプレー化の臨界電流が低下し、又溶接全般的
にみて高速溶接が可能となる等の諸効果を享受し
得ることになつた。
次に実験例を示す。
実験例 １
下記化学成分を基本組成とし、表層酸素濃度を
種々変えたCO2溶接用ソリツドワイヤ（JIS
Z3312、YGW12：1.2mmφ）を作製し、下記の条
件で溶接実験を行なつて、表層酸素濃度と短絡回
数及びスパツタ発生量の関係を調べた。
尚ワイヤ表層部の酸素濃度は、原線表面の酸化
物皮膜を一旦完全に除去した後所定量の酸化物皮
膜を形成させる方法によつて調整し、且つ各ワイ
ヤには最終段階で所定量の銅めつき処理を施し
た。
The present invention relates to a solid wire for gas-shielded arc welding, and in particular to a solid wire that has good feedability to the arc point and excellent droplet transferability. The solid wire for gas shielded arc welding (hereinafter simply referred to as wire) of the present invention can be used not only for welding mild steel, but also for welding high tensile strength steel of 50 kg class or even 60 kg class or more, or alloy steel such as Cr-Mo steel. It can also be widely applied to CO 2 , Ar-CO 2 , Ar-O 2 ,
It is used in combination with various shielding gases such as CO2 - O2 , Ar- CO2 - O2 , Ar, and He. When performing shielded gas arc welding using this type of wire, the wire is fed into the conduit tube by a feed roller, and is energized by contact with a current-carrying tip while being connected to the base metal. Welding is performed by generating an arc, and wire feedability is extremely important in keeping the arc stable and ensuring good welding workability. Further, no matter how good the feeding performance is, unless the transferability of the droplet from the wire tip toward the base material is good, a stable arc cannot be obtained. From this point of view, various studies have been conducted with the aim of improving wire feeding performance and droplet transfer performance, but none of them can be said to meet the demands of the field. For example, Japanese Unexamined Patent Publication No. 128294/1983 aims to improve wire feeding performance,
After creating microcracks on the surface of the bare wire by setting the surface oxygen concentration of the bare wire to 50 to 400 ppm, copper plating is applied, and cracks corresponding to the microcracks are created on the surface of the copper-plated wire. The aim is to improve the surface smoothness by impregnating these cracks with oil. However, as mentioned above, this invention focuses only on feeding performance, and no special consideration is given to droplet migration, so it cannot be said to be insufficient from the comprehensive viewpoint of arc stability. I don't get it. On the other hand, the oxygen concentration near the wire surface is 80
There is also a known technology to increase droplet transferability by increasing the droplet transferability to ~1000ppm and lowering the surface tension of molten steel, but in this case, only the droplet transferability is of interest and special consideration is given to wire feedability. arc stability is still insufficient. In this way, conventional technology attempts to improve arc stability by improving wire feeding performance and droplet transfer performance individually, and by simultaneously increasing both performances and their synergistic effect, arc stability is improved. It appears that no attempt has been made to improve this. In view of these circumstances, the inventors of the present invention believe that arc stability can be improved at least additively, and in some cases synergistically, by increasing wire feeding performance and droplet migration performance. We have been researching this by digging deeper into conventional technology.
As a result, if the oxygen concentration in the surface layer of the bare wire is increased above a certain value, the presence of oxygen improves droplet migration, and countless microcracks occur on the surface, reducing the ability to retain lubricant. It was confirmed that the wire feedability was improved and the arc stability could be significantly enhanced. It was also confirmed that even when plating is performed, cracks corresponding to the microcracks are formed on the surface of the plating layer, and the same effect can be obtained. The present invention was completed through further experiments based on such confirmation results, and its structure is such that an oxide is formed by oxidizing the surface layer of the bare wire, and the element is removed from the peripheral surface of the bare wire. The oxygen concentration in the surface layer is up to 2.5% relative to the wire diameter.
The main feature is that the content is 1100 ppm or more, and many microcracks are formed on the surface layer. In order to reduce frictional resistance within the conduit tube and improve feedability, the wire of the present invention increases the oxygen concentration on the surface of the bare wire to 1,100 ppm or more, and has numerous layers on the surface of the bare wire or plated wire. It reduces feeding resistance by increasing surface smoothness by forming microcracks, and improves droplet migration by lowering the surface tension of droplets by the presence of an appropriate amount of oxide. Such a wire is produced by heat-treating (annealing) the wire (bare wire) before drawing and plating to generate a grain boundary oxidation layer, and then drawing the wire with the grain boundary oxidation layer remaining. And, it can be easily obtained by performing a plating treatment after wire drawing, or by performing wire drawing after a plating treatment. That is, when wire is drawn after forming a grain boundary oxidation layer with a surface oxygen concentration of 1100 ppm or more, numerous microcracks occur on the surface as described above. Furthermore, when the surface of the bare wire is plated, a plated layer is formed along the surface where the microcracks are formed, resulting in a plated wire having countless cracks on the surface. Furthermore, even if a grain boundary oxidation layer is formed and then plated and wire drawn, cracks will occur in the plating layer at the same time as cracks occur in the bare wire, resulting in countless microcracks on the wire surface. It is possible to obtain a wire having . By the way, it has been confirmed that in order to form cracks on the wire surface that can sufficiently improve feedability, the oxygen concentration in the wire surface layer should be set to 800 ppm or more. However, at the same time, it was found that the above-mentioned surface oxygen concentration was insufficient in order to effectively improve the droplet detachability, and as will be made clear in the experimental examples described later, the oxygen concentration should be set to 1100 ppm or more. However, in the method of increasing the surface oxygen concentration by forming a grain boundary oxidation layer, if the oxygen concentration is increased too much, the grain boundary oxide layer becomes too thick and the adhesion of plating deteriorates, causing the plating layer to fail when the wire is fed. This may cause plating debris to peel off and clog the conduit tube, which may even reduce wire feeding performance. Therefore, in order to avoid these problems, it is best to suppress the surface oxygen concentration to about 8000 ppm or less, and the most preferable surface oxygen concentration in the present invention is
It ranges from 1100 to 8000ppm. In the present invention, the surface layer of the bare wire in which the oxygen concentration is specified refers to the area from the peripheral surface of the bare wire to the diameter of the bare wire.
Refers to the surface layer up to 2.5%, and the surface oxygen concentration z
(ppm) is the oxygen concentration of the entire wire x (ppm),
Let y (ppm) be the oxygen concentration of the remaining wire after polishing the bare wire surface to a depth of 2.5% or more (oxygen concentration at the center of the wire), and calculate the diameter of the bare wire as y (ppm).
Assuming that the oxygen concentration at the center of the wire excluding the surface layer up to 2.5% is also equal to y (ppm), it can be simply determined from the following equation. {π(D/2) 2 −π(D−5/100D/2) 2 }z =π(D/2) 2 x−π(D−5/100D/2) 2 y From the above formula, the following The formula is derived, π/2・z{D 2 −(D−5/100D) 2 } =π/4・D 2・x−π/4(D−5/100D) 2・y This formula is Further organizing, z・D 2 {1−(95/100) 2 } =D 2・x−D 2・(95/100) 2・y If we further organize and transform this formula, z≒10.3x−9.3y As a result, the oxygen concentration (z) in the surface layer can be determined from the oxygen concentration (x) in the entire wire and the oxygen concentration (y) in the center of the wire (excluding the surface layer). In order to increase the surface layer oxygen concentration, the removal amount of the grain boundary oxidation layer generated on the surface of the raw wire is adjusted to control the amount of remaining oxide, and then wire drawing is performed, or the oxidation of the surface of the raw wire is The most common method is to once completely remove the oxide film, then oxidize the surface again to form an oxide film, and then perform wire drawing. The present invention is constructed as described above, but the key point is that by forming a grain boundary oxidation layer on the surface of the bare wire and increasing the surface oxygen concentration to 1100 ppm or more, the surface of the plated wire can be made to have moderate micro-cracks. This improves the lubricating oil retention ability, increases the surface lubricity of the wire, and improves the feedability, and the presence of surface oxygen improves droplet migration. The combination of these two effects made it possible to significantly improve arc stability. As a result, the amount of spatter generated during welding has been drastically reduced, the bead shape and appearance have been improved, and the number of short circuits has increased in CO 2 welding, improving welding workability. In MAG welding, the critical current for spraying has been reduced, and overall welding speeds have become possible, among other benefits. Next, an experimental example will be shown. Experimental example 1 Solid wire for CO 2 welding (JIS
Z3312, YGW12: 1.2mmφ) were manufactured and welding experiments were conducted under the following conditions to investigate the relationship between surface oxygen concentration, number of short circuits, and amount of spatter. The oxygen concentration on the surface layer of the wire is adjusted by completely removing the oxide film on the surface of the raw wire, and then forming a predetermined amount of oxide film on each wire. Copper plating treatment was applied.
〔実験条件〕[Experimental conditions]
溶接条件：150(A)−21〓−30（cm／min）
シールドガス：CO2、20／min
溶接姿勢：下向きビードオンプレート
結果は第１図に示す通りであり、表層酸素濃度
が1100ppm未満では短絡回数が少なくアークが不
安定で多量のスパツタが発生するが、1100ppm以
上のワイヤでは短絡回数が大幅に増大してアーク
が安定となり、スパツタ発生量は著しく少なくな
る。また短絡回数をみると、表層酸素濃度が低い
ものではその平均値が低く且つばらつきも大きい
が、これは送給性及びアーク安定性が悪い為にこ
の様な傾向が得られたものと考えられる。
また第２，３図（何れも図面代用顕微鏡写真）
に表層酸素濃度200ppm（従来ワイヤ）と1800ppm
（本発明ワイヤ）の表面性状を、また第４，５図
にその各々のワイヤでの送給抵抗の測定例を示
す。送給抵抗測定時のコンジツトの配置は第６図
（図中１は送給装置、２はコンジツト、３は溶接
トーチを夫々示す）に示す通りである。第４，５
図に見られるように、本発明によるワイヤ（第５
図）の送給抵抗は通常のものに比べて減少してお
り送給性が改良されていることが判る。
実験例 ２
下記化学成分を基本組成とし、表層酸素濃度を
種々変えた（Ar−CO2）混合ガスアーク溶接用
ソリツドワイヤ（JIS Z3312、YGW12：1.2mmφ）
を作製し、下記の条件で溶接実験を行なつて、表
層酸素濃度とスプレー化臨界電流の関係を調べ
た。
尚ワイヤ表層部の酸素濃度は実験例１と同様に
して調整し、且つワイヤには最終段階で所定量の
銅めつき処理を施した。
Welding conditions: 150(A)-21〓-30(cm/min) Shielding gas: CO 2 , 20/min Welding position: Downward bead-on-plate The results are shown in Figure 1, and the surface oxygen concentration is less than 1100ppm. With wires of 1100 ppm or more, the number of short circuits is small, the arc is unstable, and a large amount of spatter is generated, but with wires of 1,100 ppm or more, the number of short circuits increases significantly, the arc becomes stable, and the amount of spatter generated is significantly reduced. In addition, when looking at the number of short circuits, the average value is low and the variation is large in those with low surface oxygen concentration, but this tendency is thought to be due to poor feeding performance and arc stability. . Also, Figures 2 and 3 (both are microscopic photographs used as drawings)
surface oxygen concentration of 200ppm (conventional wire) and 1800ppm
The surface properties of (the wire of the present invention) and the measurement examples of the feeding resistance of each wire are shown in FIGS. 4 and 5. The arrangement of the conduit at the time of measuring the feeding resistance is as shown in FIG. 6 (in the figure, 1 is the feeding device, 2 is the conduit, and 3 is the welding torch). 4th and 5th
As seen in the figure, the wire according to the invention (fifth
It can be seen that the feeding resistance in Figure) is reduced compared to the normal one, and the feeding performance is improved. Experimental example 2 Solid wire for mixed gas arc welding (JIS Z3312, YGW12: 1.2mmφ) with the following chemical components as the basic composition and various surface oxygen concentrations (Ar-CO 2 )
Welding experiments were conducted under the following conditions to investigate the relationship between surface oxygen concentration and spray critical current. The oxygen concentration in the surface layer of the wire was adjusted in the same manner as in Experimental Example 1, and the wire was plated with a predetermined amount of copper at the final stage.
〔実験条件〕[Experimental conditions]
溶接条件：200(A)〜320(A)
シールドガス：80％Ar−20％CO2、25／min
溶接姿勢：下向きビードオンプレート
結果は第７図に示す通りであり、表層酸素濃度
が1100ppmを境界としてそれ未満のものはスプレ
ー化臨界電流値が高いのに対し、1100ppm以上の
ものは送給性及び溶滴移行性が良好であつてアー
クが極めて安定である為、同臨界電流値は大幅に
低くなつている。
Welding conditions: 200 (A) ~ 320 (A) Shielding gas: 80% Ar - 20% CO 2 , 25/min Welding position: Downward bead-on-plate The results are shown in Figure 7, and the surface oxygen concentration is 1100 ppm. Anything less than 1100ppm has a high critical current value for spraying, while those over 1100ppm have good feeding performance and droplet transfer properties, and the arc is extremely stable, so the critical current value is It has become significantly lower.
【図面の簡単な説明】[Brief explanation of the drawing]
第１図はワイヤ表層酸素濃度と短絡回数及びス
パツタ発生量の関係を示すグラフ、第２，３図は
従来ワイヤ及び本発明ワイヤの各表面の金属組織
を示す図面代用顕微鏡写真、第４，５図は従来ワ
イヤと本発明ワイヤの送給抵抗を示すチヤート
図、第６図は送給抵抗測定時のコンジツトの配置
を示す略図、第７図はワイヤ表層酸素濃度とスプ
レー化臨界電流の関係を示すグラフである。
Fig. 1 is a graph showing the relationship between the wire surface oxygen concentration, the number of short circuits, and the amount of spatter generated; Figs. 2 and 3 are photomicrographs in place of drawings showing the metallographic structure of each surface of the conventional wire and the wire of the present invention; Figs. 4 and 5 The figure is a chart showing the feeding resistance of the conventional wire and the wire of the present invention, Figure 6 is a schematic diagram showing the arrangement of the conduit when measuring the feeding resistance, and Figure 7 shows the relationship between the wire surface oxygen concentration and the critical current for spraying. This is a graph showing.