JPH04309488A - Copper-plated steel wire for gas shielded arc welding - Google Patents

Abstract

PURPOSE:To provide the wire for gas shielded arc welding which is usable without troubles, such as interruption, even when used for long-term welding under a high current density condition to feed the wire at a high speed in order to obtain high welding efficiency and yields a weld zone having good quality free from bead meandering, etc., with the copper-plated steel wire (hereafter abbreviated as the wire) loaded into a pail pack mainly used for automatic arc welding to be executed by using a robot, etc. CONSTITUTION:The copper-plated steel wire for gas shielded arc welding to be used under the high current density condition is constituted by specifying the copper plating thickness of the copper-plated steel wire of <=1.6mm diameter to be packed into the pail pack to 0.45 to 1.40mum, specifying the content of the Ca interposed between the wire base and the plating layer on the wire surface so as to satisfy equation (1) including the copper plating thickness and specifying the oil deposition to 0.30 to 1.20g/10kg. The Ca content (mg/m<2>)<=28.1 copper plating thickness (mum)+10... equation (1).

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire for gas metal arc welding using shielding gas. Specifically, the present invention relates to a copper-plated steel wire (hereinafter referred to as wire) loaded in a pail pack mainly used for automatic arc welding using a robot etc. In order to obtain high welding efficiency, the wire is For gas-shielded arc welding, which can be used for long periods of welding without trouble such as interruptions under conditions of high current density delivered at high speeds, and which produces high-quality welds without bead meandering. It concerns wires.

0002

[Prior Art] Recently, gas-shielded arc welding has become more and more widely used as welding becomes more automated and more efficient. As a result, techniques are being developed that can increase the melting rate of wire.

For example, Ar--C, which generates less spatter,
In the O2 mixed gas method, when the current value exceeds a certain level, the penetration shape of the weld bead becomes so-called "finger-shaped" with excessive penetration with a narrow width in the center, resulting in defects such as cracks and blowholes. Although there is a problem, Japanese Patent Application Laid-Open No. 1983-1997 solves the penetration shape problem under high current density conditions by using a mixture of four types of Ar-He-CO2-O2 as the shielding gas.
A method as described in Japanese Patent Publication No. 45084 was developed, and a method was developed in which the wire was made special by Ar-CO2 welding as described in Japanese Unexamined Patent Publication No. 1-35881, and furthermore, a method was developed in which the wire was made special by Ar-CO2 welding as described in Japanese Patent Application Laid-Open No. 1-35881. Furthermore, in CO2 welding, the current density was increased. However, this problem can be solved by using a relatively small diameter (1.2 to 1.4
High current density welding methods, such as the use of metal powder-based flux-cored wire (mmφ), have been put into practical use. In addition, in both of these, the welding machine (power supply and wire feeding device) can feed the wire stably at a higher speed than before (for example, wire feeding speed, conventional 20 m/min max → 40
m/min max ) has been improved and used.

On the other hand, when such high current density conditions are adopted, the wire used is inevitably used in robots and the like, and instead of the conventional spool-wound wire weighing 20 kg or less, Wires housed in so-called cylindrical pail packs that can hold 400 kg will be widely used. The characteristics required of the wire loaded in such a pail pack are: (1) Since welding is carried out almost continuously for many hours, the wire feeding performance can be maintained for a long time without interruptions due to tip clogging, etc. It is stable over time, and (2) the runout of the wire tip is small and the weld bead does not meander.

The present inventors have already solved these required characteristics in the invention of Japanese Patent Application No. 1-258553 (hereinafter referred to as the invention of the prior application). However, as mentioned above, when the wire is used under high current density conditions where the wire is fed at a feeding speed exceeding 20 m/min, the wire according to the earlier invention cannot sufficiently cope with the situation, and the wire is also used during welding. It has become clear that problems with feeding are likely to occur. That is, it has been found that with conventional wire, welding is frequently interrupted due to tip clogging.

[0006] Here, the high current density condition means a welding current condition that exceeds the upper limit of wire feeding speed of 20 m/min in a conventional general welding machine, and the welding current value per unit cross-sectional area of the wire is approximately , that is, welding current density 340A/m
This indicates the condition of m2 or more.

[0007]

[Problems to be Solved by the Invention] The present inventors have attempted to solve the above-mentioned problems with wires used under high current density conditions or high wire feeding speed conditions and loaded into pail packs. First, we investigated what was the problem with the wire according to the invention of the earlier application. As a result, JP-A-58
- As stated in Publication No. 35068, the wire loaded in the pail pack has good straightness, and when the wire passes through the tip during welding, unlike the spool-wound wire, which has a radius of curvature in one direction. It was found that the point where the current flows from the inner wall of the chip to the wire does not tend to be fixed, but moves over a wide range of the inner wall of the chip. When the current-carrying point attempts to move in this way, sparks occur between the inner wall surface of the copper chip and the wire, but the higher the current density, the more likely sparks will occur, causing greater damage to the inner wall surface of the chip. The higher the current density, the more likely it is that a rapid change (decrease) in the current value or momentary breakage of the arc, which is thought to be caused by the difficulty in moving the current point, will occur, resulting in welding interruption. It turned out to be easier.

[0008]

[Means for Solving the Problems] The present inventors have focused on this phenomenon, and have determined the properties of the wire surface under high current density conditions (high speed wire feeding conditions) with wire loaded in a pail pack.
The relationship between adhesion substances and wire strength and feedability was experimentally investigated. As a result, the amount of Ca in the lubricant remaining between the copper plating and the iron base under the plating needs to be more strictly limited than in the case of the prior invention, and the amount (thickness) of the copper plating must be increased. Under current density conditions (high-speed wire feeding conditions), it is basically necessary to maintain it above a certain value;
Furthermore, it was found that the amount of oil attached to the wire surface, as well as the tensile strength or tensile breaking strength of the wire, mutually greatly influenced the feedability and other properties of the wire loaded in the pail pack. .

That is, the gist of the present invention is that the copper plated steel wire with a diameter of 1.6 mm or less to be loaded into a pail pack has a copper plating thickness of 0.45 to 1.40 μm.
m, the amount of Ca interposed between the wire base and the wire surface plating layer satisfies formula (1) including the copper plating thickness, and the amount of oil adhesion is 0.30 to 1.20 g/10 kg. Copper-plated steel wire for gas-shielded arc welding used in high current density conditions is characterized by:

[0010] Ca amount (mg/m2)≦28.1 Copper plating thickness (μ
m ) + 10...Equation (1) Furthermore, in the present invention, by setting the tensile strength in the case of solid wire and the tensile breaking load in the case of flux-cored wire to a certain range, welding can be performed with less runout at the tip of the wire. The structure is such that a high-quality welded part with no meandering bead can be obtained.

[0011] The basic effects of the amount of Ca interposed between the wire base and the wire surface plating layer have already been clarified in the specification of the aforementioned prior invention by the present inventor.

0012

[Operation] First, the reason why the amount of Ca interposed between the wire base and the wire surface plating layer in a copper-plated steel wire is regulated in relation to the copper plating thickness is as follows. That is, in the case of a pail pack wire, the straightness is so good that movement of the energizing point between the inner wall of the chip and the wire occurs frequently with short sparks, but if the amount of Ca is large, the sparks tend to continue due to the presence of Ca ions. A short spark turns into a long spark, damaging the tip in a short period of time, and the formation of a long spark means that it is inhibited from moving to a new energization point, resulting in phenomena such as the welding arc suddenly breaking. .

The present inventors have experimentally confirmed that this phenomenon increases rapidly under high current density conditions. These phenomena are observed when the welding current value drops momentarily and intermittently even though the wire is being fed smoothly, but if this condition becomes severe, the arc suddenly breaks and welding is interrupted. That will happen. In this case, if the copper plating thickness is thick, the extent to which these phenomena appear will be reduced.

FIG. 1 is a diagram showing the relationship between the amount of Ca, the thickness of copper plating, and these phenomena, and the results of the long-term welding feedability test show that the higher the amount of Ca, the more poor feedability occurs in a short time. but,
It is shown that the thicker the copper plating, the longer the time. Note that the experimental conditions were as follows:
Z3312-YGW11 applicable product, diameter 1.2mm, welding conditions are 450A, 40V, Ar + 10% CO2 25
liter/min and wire feeding speed is 25m/min
, downward bead-on-plate welding at a current density of about 400 A/mm2.

[0015] The test wire was taken from a pail pack (for 250 kg) loaded with 50 kg with a general reverse twist.
Welding was carried out using a 6 m long conduit cable and a pistol torch via an extraction device and a conventional feed device. In addition, in order to conduct a long-term feedability test, the torch was fixed and the welding test plate was placed on a rotating jig and rotated so that weld beads formed in continuous layers. Welding was carried out almost continuously for a maximum of 20 cycles, with 5 minutes of continuous welding being considered as one cycle, and welding was performed until the end without any problems with feedability, or welding was interrupted due to feed failure midway through, or welding was interrupted at the end. Welding was not interrupted until then, but the determination was made by checking whether the phenomenon of instantaneous decrease in arc current occurred many times or whether the arc became unstable. In this case, the amount of oil attached to the wire was set to 0.5 to 1.0 g/10 kg.

Although FIG. 1 shows experimental data for a wire diameter of 1.2 mm, results showing almost the same tendency were obtained for other wire diameters of 1.4 mm and 1.6 mm, as well as for flux-cored wire. Ta. Ca is in the form of metal soap containing Ca, which is a lubricant used in wire drawing, or in the case of annealing, it is thermally decomposed to form CaO or Ca(OH).
It remains in the form of 2. The method for quantifying the amount of Ca in wire is 1.
00g of wire was cleaned with ethyl alcohol for 5 to 10 minutes.
The wire is cut into a length of cm, and the wire is boiled in dilute hydrochloric acid (7%) for 10 minutes to dissolve and filter Ca, and then Ca is quantified using an atomic absorption spectrophotometer. In this case, the steel base will also melt to some extent, but since the amount of Ca contained in general steel is small,
All the detected amounts of Ca are taken as the amounts of Ca interposed between the steel base and the wire surface plating layer.

Various methods can be considered to control the amount of Ca interposed between the wire surface plating layer and the steel base.
The most effective method is the pretreatment method before plating, and the bipolar electrolytic degreasing method is particularly effective. However, in addition to this method, there are methods such as cathodic electrolytic pickling, normal anodic electrolytic degreasing, cleaning methods after using lime soap as a lubricant (cleaning method with pressure water, mechanical methods such as brushing, etc.). ) is effective in addition to the above plating pretreatment method. Note that by sufficiently controlling the concentrations of the degreasing solution and the pickling solution, it is possible to further reduce the amount of Ca. C as a residue on the wire surface
In addition to a content, Na, Ba, K content, etc. are also harmful, but it is desirable that these are all reduced to 30 mg/m2 or less. The reason why the copper plating thickness was restricted to 0.45 μm or more was that under high current density welding conditions, the wire inevitably
Although the welding is carried out at a high speed of 0 m/min or more, intermittent long-term welding with high-speed feeding is thought to be caused by heating of the chip or damage to the inner surface of the chip, which is not thought to be significantly related to Ca residual content. It was observed that a defective phenomenon occurred, and it was found that this phenomenon was greatly reduced by increasing the copper plating thickness to 0.45 μm or more. On the other hand, the reason why the copper plating thickness is set to 1.40 μm or less is because the copper content in the weld metal increases, which adversely affects mechanical properties (such as an increase in tensile strength).

Control of the copper plating thickness is easy and can be achieved by changing the plating size, plating current, time, etc. It is necessary to limit the amount of oil adhesion to 0.30 g/10 kg or more in order to reduce the frictional resistance at the conduit and tip during welding and improve feeding performance, but in the case of pail pack wire, especially 1. If it exceeds 20g/10kg, it is not preferable. When loading the wire into the pail pack, it passes through a straightening roller to ensure straightness, but it is 1.20
When the amount of oil adhesion exceeds g/10 kg, slippage phenomenon on the rollers tends to occur, and small waviness tends to occur in the loaded wire. This impairs the two characteristics necessary for the pail pack wire: deflection of the wire tip and good feeding performance over a long period of time.

The tensile strength of the wire affects both the long-term feedability of the pail pack wire and the wire runout during welding in conjunction with the amount of oil adhesion and the amount of Ca. In other words, if the tensile strength of each wire diameter is less than the lower limit, the rigidity of the wire is small;
It tends to follow the bends of the conduit during feeding, and the wire tends to get curled, causing the tip of the wire to run out. On the other hand, if the upper limit is exceeded, the feeding resistance will increase at the bent portion of the conduit during feeding, which will worsen the feeding performance. The tensile strength of the wire also affects the amount of oil adhesion during manufacturing when loading the wire into a pail pack; if it is too low, it tends to cause waviness, and if it is too high, stable loading cannot be performed.

In the case of a flux-cored wire, the inside of the wire is filled with flux, and the tensile strength, which is calculated by dividing the tensile breaking load by the cross-sectional area, cannot indicate the rigidity of the wire.
The tensile breaking load (kgf) of each wire diameter was specified as is. Note that these tensile strengths or tensile breaking loads can be set by changing the dimensions and components of the raw wire or pipe, whether or not annealing is performed in the manufacturing process, the annealing diameter, and the annealing conditions.

[0021]

EXAMPLES Below, the method of manufacturing the wire of the present invention will be explained in detail using examples. First, the solid wire has an original wire diameter of 5.5 mm, chemical components C: 0.06%, and Si: 0.72.
%, Mn: 1.68% hot rolled steel wire was used as a raw wire, and after removing scale by mechanical descaling, it was pickled, immersed in a suspension of lime soap as a lubricant, coated and dried, and wire drawn. 2.0-2.4m using Na-based metal soap as a lubricant
After drawing the wire to m, the presence or absence of washing with pressure water shown in Table 1,
Wires of the present invention and comparative wires having product diameters of 1.2 to 1.6 mm were manufactured with or without annealing, through a plating pretreatment process, and a plating process, and were subjected to the long-term welding feedability test described above. For flux-cored wire, chemical component C: 0.06%,
A 12 mm raw pipe containing Si: 0.01% and Mn: 0.32% was filled with flux and drawn to 2.4 to 4 mm using Ca-based metal soap. After undergoing the cleaning with pressure water, annealing, pre-plating process and plating process shown in 1), the product diameter is 1.2~1.
A 6 mm wire of the present invention and a comparative wire were manufactured, and the long-term welding feedability test described above (the evaluation method was also the same) was conducted. The results are shown in Tables 1 and 2.

[0022]

[Table 1]

[0023]

[Table 2]

[0024] Here, the annealing conditions are 550 to 750°C x 3
Nitrogen was used as the atmospheric gas. The plating pretreatment and plating conditions were as follows. 1) Bipolar electrolytic degreasing 50A/piece, 7-12V solution NaOH 100g/liter liquid temperature
80℃, line speed 50-120m/min2) Cathode electrolytic pickling 110A/piece, 7-12V Solution HCl 10-20g/liter Liquid temperature
25℃, line speed 50-80m/min 3) Plating 70-130A/piece, 7-12V Solution KCN 5-20g/liter liquid temperature
60° C., wire speed 50 to 80 m/min, and a vegetable lubricant was used as the final wire drawing lubricant.

As shown in Tables 1 and 2, wires manufactured under various wire manufacturing conditions with wire characteristics that satisfy all the requirements of the present invention gave good results throughout the long-term welding feedability test. has been obtained (○ mark Test No.
1-13). However, as shown in the comparative wires, those with low copper plating thickness (No. 14, 15 and No. 21)
, Ca amount - copper plating thickness does not satisfy formula (1) (
No. 16, 17, 20 and 22) are wire feeding interruptions (
(x mark), or there was no interruption but the supply became unstable (△ mark), or the arc current decreased many times (▲ mark). Also, No. No. 18 was discontinued due to an inappropriate amount of oil. In addition, No. In No. 19, the wire tensile strength was too low, and when loaded into the pail pack, the wire had large undulations, causing bead meandering during welding, so welding was discontinued.

[0026]

Effects of the Invention According to the present invention, when welding with a pail-packed wire for high current density welding, which has recently been developed and is being used to improve the efficiency of welding, there is no problem with feeding performance even during long-term continuous welding. The effect is that a good welded part can be obtained without bead meandering due to wobbling of the tip of the wire.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the results of a long-term welding feedability test when the amount of Ca interposed between the wire base and the wire surface plating layer and the copper plating thickness were varied.

Claims

[Claims] Claim 1: Diameter 1.6 loaded in a pail pack
In a copper-plated steel wire of 0.45 to 1.40 μm or less, the copper plating thickness is 0.45 to 1.40 μm, and the amount of Ca interposed between the wire base and the wire surface plating layer includes the copper plating thickness (1) Satisfies the formula and has an oil adhesion amount of 0.30 to 1
．． A copper-plated steel wire for gas-shielded arc welding used under high current density conditions, characterized by a weight of 20g/10kg. Ca amount (mg/m2)≦28.1 Copper plating thickness (μ
m)+10...Equation (1) 2. The copper-plated steel wire for gas shielded arc welding according to claim 1, wherein the wire is a solid wire having a tensile strength within the following range. Wire diameter: 1.6mm 70-100kgf/
For mm2 1.4mm 75-115kgf/m
For m2 1.2mm 80-130kgf/mm
2 3. The copper-plated steel wire for gas-shielded arc welding according to claim 1, which is a flux-cored wire having a tensile breaking load within the following range. For wire diameter 1.6mm: 75-110kgf1
．． For 4mm: 65~90kgf For 1.2mm: 55~80kgf