JPH09168890A - Gas shielded arc welding steel wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fully automatic and semiautomatic welding steel wire having improved weldability. SOLUTION: This welding steel wire is composed of, by wt., 0.02-0.15% C, 0.3-2.0% Si, 1.0-3.0% Mn, <=0.03% P, <=0.03% S, 0.1-0.50% Cu, 0.01-0.25% Al, 100-800ppm O and the balance Fe. Moreover, the base material of the steel wire is composed of a steel tube, and oxygen concentration is raised in the central part within the range of 50μm in the direction from the inner to outer surface of the steel tube.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel wire for gas shielded arc welding, which has excellent arc stability and spatter resistance and is used for full-automatic and semi-automatic welding of steel.

[0002]

2. Description of the Related Art In recent years, welding robots, automatic welding machines, etc. have been introduced to promote high-speed automation of welding. Along with this, higher requirements have been placed on the performance of welding wires and welding workability. Has been done. In general, 0.8 to 2.4 m for CO ₂ gas shield arc welding, MIG welding, etc.
mφ copper-plated welding steel wire is used.
These welding wires are usually used for welding in a state of being wound on a spool or a bobbin or loaded in a pail pack. When these wires are used, they are installed in a feeder, which is an auxiliary device of the welding machine, and welding is performed through a flexible conduit cable, a welding torch, and a contact tip extending 3 to 20 m through a feeding roller. The gas shielded arc welding method has a tendency to expand its application range by taking advantage of its characteristics of high efficiency, high quality and low cost as compared with other welding methods. However, although the gas shielded arc welding method has the characteristics of high efficiency and high quality, there are problems such as frequent occurrence of spatter during welding. Therefore, many measures and studies have been made to reduce the amount of spatter generated in the gas shield arc welding method. Improvement of first welding power supply characteristics, conversion of the shielding gas from the CO ₂ to Ar-based gas, a method of increasing the oxygen concentration in the wire surface layer portion are known, improved welding power supply characteristics and CO ₂
Although it is possible to expect an effect such as conversion from Ar to Ar gas, it is economically expensive and not preferable. On the other hand, many techniques for increasing the oxygen concentration have been studied from the viewpoint of the welding wire. These techniques are intended to reduce arc stability and spatter by the action that wire oxygen lowers the surface tension of molten metal. That is, oxygen lowers the surface tension of the molten metal, changes the electric discharge phenomenon, and the droplets suspended at the tip of the wire atomize the droplets even with a slight pinch force. It is considered that the fine droplets regularly move to the crater and the arc stability is improved. As a technique for increasing the wire oxygen, for example, JP-A-60-406
Japanese Patent Publication No. 85, Japanese Patent Publication No. 3-16237, etc. disclose methods for increasing the oxygen concentration in the wire surface layer portion. As a means for increasing the oxygen concentration in the surface layer of the wire, the wire is annealed in an atmosphere in which the partial pressure of the oxidizing gas is changed to form an oxide film on the surface, and then the pickling condition is controlled to obtain an appropriate amount. This is a method of leaving an oxide film, but if it is tried to increase the surface oxygen concentration, it will be 4
It is not economical because it requires annealing for more than an hour. In addition, since complicated heat treatment and pickling control are required in the manufacturing stage, the plating peels off during welding and clogs the chip, which hinders wire feedability and makes the arc unstable and frequent spattering. Problems arise. In addition, JP-A-7-51
No. 182 contains a certain amount of oxide in the plating layer,
A technique aimed at improving spatter resistance has been disclosed, but since this technique takes in a plating solution together with an oxide, the rust resistance of the wire becomes a problem. Further, a method of mechanically providing irregularities on the wire surface to apply iron oxide or Japanese Patent Laid-Open No. 5-69181 discloses wire drawing using a lubricating oil mixed with iron oxide powder to form iron oxide in the concave portions of the plating layer. A method of incorporating flour is disclosed. All of these have in common that iron oxide is used as the oxygen source, but when iron oxide is used, an arc is generated between the tip and the wire during welding and arc becomes unstable, and further iron oxide powder is contained in the tip. This is an unfavorable method because it obstructs clogging welding.

As described above, the means for increasing the oxygen concentration in the surface layer of the wire has various restrictions and is not always practical. As a solution to this, a wire that increases the oxygen concentration in the center of the wire,
Means have been disclosed for consideration. Japanese Examined Patent Publication No. 48558/1992 discloses a method for producing a solid wire by forging both edges of a heated steel strip and drawing a steel pipe having an oxide layer on the inner surface. Since this manufacturing method is premised on forge welding, there is a problem that the heating temperature is as high as about 1100 ° C. to 1400 ° C., and therefore it is difficult to adjust the amount of the oxide layer on the inner surface of the wire. Further, in JP-A-1-170598, in a wire having a two-layer structure of a wire central part having a high oxygen concentration and an outer layer part having a low oxygen concentration, the cross-sectional area ratio of the central part,
A solid wire technique is disclosed in which the spatter generation amount is reduced by defining the central part oxygen concentration, the central part and outer layer part oxygen concentration ratio, and the total oxygen concentration of the wire. This technique requires a special manufacturing method because the steel wire has a two-layer structure with different oxygen concentrations and the central area has a large cross-sectional area ratio of 10 to 60%.

As described above, although many conventional techniques for suppressing arc stability and spatter generation amount by increasing wire oxygen have been disclosed, there are many problems from the viewpoint of spatter suppression and economics.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the conventional wire manufacturing method, arc stability and reduction of spatter. An improved fully automatic and semi-automatic welding steel wire is provided.

[0006]

Means for Solving the Problems The present inventors have obtained the following findings as a result of repeated basic research aiming at solving the above-mentioned various problems. A hollow method that does not require long-time annealing to increase surface oxygen concentration, complicated heat treatment or pickling control in the manufacturing stage, or prevents iron oxide from adhering to the wire surface that causes chip clogging. After heating the steel pipe to form an oxide layer on the inner surface, it was considered to perform wire drawing to obtain a steel wire for gas shield arc welding. An economical and effective solid wire is provided by identifying a component that easily forms an oxide layer and a component having a high sputtering amount suppressing effect on the inner surface of the hollow tube and then identifying the oxide layer.

That is, (1) C: 0.02 to 0.15% [wt%, the same applies hereinafter], Si: 0.3 to 2.0%, Mn: 1.0 to 3.0
%, P: ≤ 0.03%, S: ≤ 0.03%, Cu: 0.
1 to 0.50%, Al: 0.01 to 0.25%, O: 1
A gas containing 0 to 800 ppm, the balance being Fe, and the material of the steel wire being a steel pipe, wherein the O concentration is increased by the central portion in the range of 50 μm from the inner surface to the outer peripheral direction of the steel pipe. Steel wire for shield arc welding (2) Steel wire for gas shield arc welding according to (1), containing Ti: 0.01 to 0.3% (3) Ni: 0.5 to 2%, Cr: 0. 05-2%, M
o: Steel wire for gas shield arc welding according to (1) or (2), containing one or more of 0.05 to 1% (4) A depth of 50 μm in the outer peripheral direction from the inner surface of the steel pipe. Is a steel wire for gas shielded arc welding according to (1), (2) or (3), which comprises iron oxide.

The present invention limits the wire component and the wire oxygen amount to 100 to 800 ppm, and the oxide formed by concentrating the oxygen in the central portion of the wire effectively atomizes the droplets. It is possible to improve the arc stability and suppress the amount of spatter generation. In order to confirm the effect of the existence position of oxygen on the arc stability, in a wire having almost the same average oxygen concentration, (a) a case where an oxide layer is formed on the surface layer of the wire to increase oxygen, and (b) the wire When the wire having an oxide layer formed at the center was compared and examined, it was found that the case (b) in which oxygen was present at the wire center was superior in arc stability. That is, the arc during welding selectively moves the shortest distance between the droplet and the molten metal. After the droplet grows to a certain size and migrates, the arc migrates to the tip of the wire and the shortest part of the molten metal. At this time, it is considered that, when the wire oxygen source is in the central portion of the wire and in the peripheral portion, the arc transition is smooth when the oxygen source is in the central portion. Especially,
In the case of carbon dioxide welding, which has a shorter arc length than MAG welding using Ar as the main gas, this effect effectively contributes to the improvement of arc stability. However, if the amount of oxygen in the central portion of the wire is too large, the amount of oxide covering the molten tip of the wire after the droplet transfer is too large, and the above-mentioned arc transfer to the distal end of the wire does not become smooth. The oxides to be formed into wires are roughly classified into an outer oxide layer and an inner oxide layer.However, in order to form the inner oxide layer, it is necessary to control and adjust the oxygen concentration of the heating atmosphere to a low level. Requires heating for hours. However, in the case of the outer oxide layer, the oxygen concentration can be effectively increased by heating in the atmosphere for a short time. Since these oxide layers are electrically poor conductors, when an oxide layer is applied to the wire surface, the amount of formation is naturally limited because the electrical conductivity during welding deteriorates. On the other hand, by forming an oxide in the central portion of the wire, such an adverse effect on the electrical conductivity does not occur and a sufficient oxide layer can be formed.
In order to concentrate the oxide layer on the central part of the wire, it is necessary to form the oxide layer 2 on the inner surface of the hollow pipe as shown in FIG. 1 and then perform wire drawing to obtain the wire (1.2 mmφ) shown in FIG. it can. The oxide layer of about 50 μm formed in the central portion of the pipe was elongated by the subsequent wire drawing, and
With a wire finished to about 2 mm, it becomes indistinguishable from the surroundings even when magnified 50 times. Since the adjustment of the oxygen amount is proportional to the scale thickness as shown in FIG. 3, it can be easily performed by adjusting the heating temperature and the heating time. In this way, the sputter amount of the wire with the changed wire oxygen amount is
As shown in FIG. 4, the amount of oxygen can be reduced in the range of 100 to 800 ppm. FIG. 5 shows an oxygen analysis result by EPMA line analysis of the wire cross section of a wire of Example No. 6 of the present invention (oxygen amount: 223 ppm) described later. As is clear from FIG. 5, a large amount of oxygen is concentrated in a narrow area in the center of the wire, and this concentrated oxygen effectively acts on improving arc stability and reducing spatter as described above. is there.

The reasons for limitation of the present invention will be described below. (C: 0.02 to 0.15%) C is an essential component for obtaining the strength of the weld metal, but it has the effect of improving droplet transferability, and if it is less than 0.02%, mild steel / high As the weld metal of the tensile steel, the strength is insufficient, the droplets become coarse and large spatters are generated, and if it exceeds 0.15%, the crack resistance of the weld metal is significantly deteriorated. (Si: 0.3 to 2.0%) Si is indispensable as a deoxidizing element and is effective in increasing the yield strength of the weld metal. The present invention has the effect of efficiently forming oxides and effectively increasing oxygen. However, if it is less than 0.3%, deoxidation is insufficient, and if it exceeds 2.0%, the toughness of the weld metal decreases, which is not preferable. (Mn: 1.0 to 3.0%) Mn is added as a deoxidizer together with Si and is effective for oxide formation, but if it is less than 1.0%, it causes pits and blow holes. 3.
If it exceeds 0%, the amount of spatter increases and the crack resistance deteriorates, and weld cracking is likely to occur. (P: ≤ 0.03% S: ≤ 0.03%) P is required to be less than 0.03% from the viewpoint of preventing cracking.
Further, S causes the occurrence of hot cracking, so it is necessary to make S less than 0.03%. (Cu: 0.10 to 0.50%) When Cu is less than 0.10%, it is difficult to completely expose the plating base (Fe base), which causes rust on the wire surface.
If it exceeds 0.50%, the plating is peeled off inside the feeding roller portion or inside the conduit liner during welding, which deteriorates the feeding performance. (Al: 0.001 to 0.10%) Al is an essential element for forming an oxide layer, and has an effect of increasing droplet viscosity. If the content is less than 0.001%, the effect is insufficient, and if it exceeds 0.10%, the toughness of the weld metal decreases, which is not preferable. (O: 100 to 800 ppm) As described above, O is important in atomizing the droplets to improve welding workability and reduce the amount of spatter generation. 100p in the configuration of the present invention
The effect is exhibited at pm or more. However, 800pp
If it exceeds m, not only the effect of O on the droplet transferability decreases, but also CO gas is significantly generated during the droplet transfer, a boiling phenomenon occurs at the tip of the droplet, and the arc stability deteriorates. Also, the effect of weld metal on oxygen cannot be ignored,
The upper limit was set to 800 ppm in order to increase the oxygen content of the weld metal and deteriorate its impact toughness. The amount of oxygen that has the best arc stability and droplet transferability is about 400 to 650 ppm, which is a preferable range. It should be noted that it is preferable that the existing positions of oxygen are concentrated in the center of the wire rather than in the surface of the wire. This is because if a large amount of oxygen is concentrated on the wire surface layer portion as described above, problems such as wire feedability and plating peeling are likely to occur. Will be resolved.

In addition to the above-mentioned components, the amount of spatter generation can be suppressed more effectively by adding an appropriate amount of Ti. If necessary, one or more of Ni, Cr, and Mo can be added in an appropriate amount. (Ti: 0.05 to 0.3%) Ti is added as a deoxidizing element, and has the effect of refining the microstructure of the weld metal by the formation of oxides, improving the toughness, and refining the droplets, and the amount of spatter generation. Has the effect of suppressing If it is less than 0.05%, the effect of suppressing spatter cannot be obtained, and if it exceeds 0.3%, it becomes difficult to manufacture the wire. (Ni: 0.5 to 2.0%) Ti is effective in increasing the ductility and toughness of the weld metal, and if less than 0.5%, it has no effect, and if it exceeds 2.0%, the ductility deteriorates. (Cr: 0.05 to 1.0%) Cr has the effect of improving the ductility and cracking resistance of the weld metal. If it is less than 0.05%, it has no effect, and if it exceeds 1.0%, the ductility deteriorates and cracking occurs. Cause of. (Mo: 0.05 to 1.0%) Mo is effective in increasing the strength and ductility of the weld metal, and is less than 0.05%, and if it exceeds 1.0%, ductility deteriorates and causes cracking. Become. As a means for concentrating oxygen in the central portion of the wire (with a depth of 50 μm from the inner surface of the hollow steel pipe to the outer peripheral direction), an oxide layer is formed on the inner surface of the hollow pipe, and then wire drawing / The method of working to obtain a wire is economically and practically recommended. In this case, in order to secure a predetermined oxygen concentration, the depth of the oxide layer needs to be about 50 μm. The oxide layer to be generated is not limited as long as it is an oxide that can secure the amount of oxygen, but the oxides of the constituent elements of the wire components are SiO ₂ , MnO, Al ₂ O ₃ , and T.
Although iO ₂ , Cr ₂ O _{3 and the} like can be considered, an iron oxide scale that is effective and easily produced even when the composition of the heating atmosphere such as the air is not limited is most economical and recommended. For iron oxide scale, FeO, Fe ₂ O ₃ , Fe ₃
There is no problem with O ₄ and its mixed oxide. The heating conditions for forming these iron oxide scale layers are 6
The heating may be carried out at 00 ° C. for about 1 hour, and usually it may be carried out as an annealing step for softening the hardening by drawing.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION

(Example) Various hollow steel pipes having the chemical composition shown in Table 1 (outer diameter 1
(2.7 mmφ, wall thickness 2.5 mm), a hollow steel tube → intermediate wire drawing → annealing → pickling → plating → finish wiredrawing → product manufacturing process, and a wire having a diameter of 1.2 mmφ was manufactured as a prototype. Welding was performed on a mild steel base material using these wires, and the presence or absence of pores and cracks was evaluated by welding workability and X-ray transmission test. The oxide layer was formed inside the hollow steel pipe by an annealing process. The conditions were atmospheric air, the temperature was 600 ° C., and the heating time was changed. In the evaluation of the obtained wires, the arc stability and the droplet transferability were investigated as arc stability. As for the amount of spatter, the results shown in Table 1 were obtained by weighing the amount of spatter captured in the copper collection box. Welding is performed with a CO ₂ gas shield under the welding conditions of 320A-32V-30.
Downward bead-on-plate welding was performed at cm / min, and the distance between the tip and the base metal was constant at 20 mm. Regarding the amount of spatter, commercially available wire is usually 2.0 g under these welding conditions.
Since it is around / min, 1.5 g / min in the present invention
The following were accepted.

[0012]

[Table 1] All of Nos. 1 to 10 of the invention examples showed good welding workability, and the amount of spatter was 1.5 g / min or less.

In Comparative Example No. 11, since the amount of C in the wire was small, the sputtered grains were large and the arc was stable, but the sputtered amount was increased.

In Comparative Example No. 12, the amount of oxygen in the wire was proper, but the amount of Mn in the wire was small, so that pits and blowholes were generated in the weld bead.

In Comparative Example No. 13, the scale thickness is large, the oxygen amount exceeds the upper limit, the arc is unstable, and spatter frequently occurs.

In Comparative Example No. 14, the amount of Si in the wire was too large, the arc became unstable, and large-sized spatters frequently occurred.

In No. 15 of the comparative example, the amount of oxygen in the wire was appropriate, but the amount of C in the wire was large and a large amount of spatter occurred, and at the same time weld cracking occurred.

In Comparative Example No. 16, the amount of oxygen in the wire was insufficient, the arc stability was lacking, and a large amount of spatter was observed.

In Comparative Example No. 17, the amount of wire Al is too large, the amount of oxygen increases, and the amount of sputtering increases.

Comparative Example No. 18 was poor in arc stability and sputtering amount due to insufficient amounts of Si and oxygen.

Comparative Example No. 19 has a proper amount of oxygen,
The arc stability and the amount of spatter are good, but cracks occurred in the weld metal due to the large amount of Mo.

Comparative Example No. 19 has an appropriate amount of oxygen,
The arc stability and spatter amount were good, but cracks occurred in the weld metal because the S amount exceeded the specified value.

[0023]

According to the steel wire for gas shielded arc welding of the present invention, as a means for increasing the oxygen concentration in the central portion of the wire, the hollow steel pipe is drawn, so that the annealing process is carried out at a temperature of about 600 ° C. in an atmospheric atmosphere. By setting the temperature, it becomes possible to efficiently increase oxygen, and the conventional controlled atmosphere adjustment, annealing temperature of 700 ° C. or higher and long-term temperature control are not required, and the amount of oxygen in the wire can be easily increased. It is possible to improve the arc stability and reduce the spatter.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a hollow pipe.

FIG. 2 is a cross-sectional view of a wire obtained by wire drawing after forming an oxide layer on the inner surface of a hollow pipe.

FIG. 3 is a diagram showing a relationship between an inner surface scale thickness and a wire oxygen amount.

FIG. 4 is a diagram showing a relationship between a wire oxygen amount and a sputtering amount.

FIG. 5 is a view showing oxygen distribution by EPMA in the cross section of the wire of Example No. 6;

[Explanation of symbols]

 1 pipe 2 oxide layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location C22C 38/16 C22C 38/16 (72) Inventor Tsuyoshi Hirano 3-5-4 Tsukiji, Chuo-ku, Tokyo No. Nippon Steel Welding Industry Co., Ltd.

Claims (4)

[Claims] 1. C: 0.02 to 0.15 in% by weight
%, Si: 0.3 to 2.0%, Mn: 1.0 to 3.0
%, P: ≤ 0.03%, S: ≤ 0.03%, Cu: 0.
1 to 0.50%, Al: 0.01 to 0.25%, O: 1
The content of Fe is 0.00 to 800 ppm, the balance is Fe, and the material of the steel wire is a steel pipe, and the O concentration is increased by the oxide layer formed in the central portion of the steel pipe in the depth direction of 50 μm from the inner surface to the outer peripheral direction. Steel wire for gas shielded arc welding characterized by the fact that 2. The steel wire for gas shielded arc welding according to claim 1, containing Ti: 0.01 to 0.3% by weight. 3. Ni: 0.5 to 2%, C in weight%
The steel wire for gas shield arc welding according to claim 1 or 2, which contains one or more of r: 0.05 to 2% and Mo: 0.05 to 1%. 4. The oxide layer comprises an iron-based oxide.
The steel wire for gas shielded arc welding according to claim 2 or claim 3.