JP2000288769A - Steel wire for gas shield arc welding and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a feedability of a steel wire for gas shield arc welding in the whole automatic and a semi-automatic welding in a conduit tube. SOLUTION: In the steel wire for gas shield arc welding, grain boundary oxidized layer with annealing and copper plating 2 are applied on the surface of the steel basis material, and in the copper plating 2, potassium is contained and also, sodium and/or tin are contained and in the copper plating 2,100-6000 ppm potassium content A, 100-4000 ppm sodium and/or tin contents B and 160-9000 ppm A+B and contained. Further, phosphorus in the copper plating, is contained at 10-1000 ppm, and the copper plating has the crack crossed to the longitudinal direction of the wire and on the wire surface, liquid lubricator is stuck.

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, such as fully automatic and semi-automatic welding, which has excellent feedability in a conduit tube.

[0002]

2. Description of the Related Art Generally, a gas shielded arc welding is performed with a pressure of 0.1 mm.
8 to 2.0 mm welding steel wire is used,
At the time of welding, it is installed on a feeder, which is an auxiliary device of the welding machine, and is passed through a feed roller and welded through a conduit tube having a length of about 3 to 20 m. Therefore, it is necessary to supply the wire at a constant speed in the conduit tube. However, since contact resistance with the conduit liner, torch, and tip and resistance at the bent portion of the conduit tube act, the feeding speed becomes non-uniform, and welding defects such as instability of the welding arc occur. For this reason, conventionally, a technique to improve the feedability by improving the lubricating ability by improving the lubricating ability by forming fine cracks on the surface and impregnating it by drawing wire after forming grain boundary oxidation on the steel wire surface, arc stability on the surface Techniques for adhering the promoting element have been proposed. As described above, the welding steel wire is required to have both the feeding property and the arc stability in the conduit tube.

[0003]

Problems to be Solved by the Invention JP-A-60-2315
In Japanese Patent No. 90, the wire surface layer is oxidized to form grain boundary oxidation, and the feedability and arc stability are improved by increasing the amount of oxygen in the surface layer and forming small cracks in the surface layer. In this case, it is necessary to adjust the oxygen content of the surface layer to 1100 to 8000 ppm. However, the grain boundary oxidation has a large variation in the longitudinal direction and the circumferential direction due to the heat treatment. There was a problem in stably manufacturing such that some parts disappeared. In Japanese Patent Application Laid-Open No. 54-141349, the flatness of the wire surface is specified to reduce the resistance to the conduit tube and improve the feedability. In this case, there are conditions such as the forced lubrication drawing method and the use of a high-viscosity lubricant, and operating know-how such as the need to properly adjust the yield stress of the wire and the pressure of the lubricant is required. It was difficult to operate. Further, as an invention in which an element is added during copper plating of a welding wire, addition of potassium in Japanese Patent Application Laid-Open No. 63-149093 has been proposed. Potassium is an element that surely stabilizes the arc and improves the feedability, but recently a higher level is required in order to cope with higher tensile strength, and the present invention has become unable to cope with it. Further, since potassium is contained in a form taken in between copper particles, it is difficult to uniformly distribute potassium during plating. However, from the scope of the claims and the description, potassium is contained in the entire wire by 0.5 to 2%.
It is clear that there is an appropriate range of 0 ppm, and it is clear that it is necessary to control potassium to a predetermined amount. Therefore, it is considered that there is considerable know-how in operation. Since the control method is not described, it is difficult for a person skilled in the art to easily implement the control method, and it has become impossible to cope with the current high quality. As described above, although many techniques for improving the feedability have been proposed, there remains a problem to be applied stably in actual operation.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and its gist is to provide a steel wire for gas shielded arc welding, a grain boundary oxide layer formed by annealing on a surface of a steel substrate, It has plating, contains potassium in the copper plating, contains one or more of sodium or tin, and has a potassium content A: 10 based on the copper plating.
0 to 6000 ppm, content of at least one of sodium or tin B: 100 to 4000 ppm, and A +
B contains 160 to 9000 ppm, further contains 10 to 1000 ppm of phosphorus in the copper plating, the copper plating has cracks crossing in the wire longitudinal direction, and a liquid lubricant is attached to the wire surface. A method for producing a steel wire for gas shielded arc welding and a steel wire for gas shielded arc welding, comprising:
Wire drawing to about 3 mm, an oxide layer is formed on the surface by annealing, and then the annealed wire is made mainly of copper pyrophosphate and potassium pyrophosphate, and further, sodium pyrophosphate,
Electroplating is performed using an aqueous solution containing at least one type of tin pyrophosphate to form a copper-plated wire, and the copper-plated wire is subjected to wire drawing with a reduction in area of 3 to 20% per die. Wherein the flow rate is 5 to 60 m / min.

Since the feedability in a conduit tube is governed by the lubricating ability of the surface, the present inventor has been keenly promoting research on improving the lubricating ability of the surface and maintaining the lubricating ability at the time of feeding. It has been found that it is most effective to have a large number of cracks crossing in the directions and to contain the liquid lubricant. It is known that this crack can be generated by annealing in the manufacturing process to form grain boundary oxidation on the surface layer of the wire and then performing copper plating and wire drawing, but the degree of grain boundary oxidation varies. In order to stably generate a crack without being affected by the partial disappearance of the grain boundary oxide layer in the plating pretreatment, one or more elements from among sodium and tin in addition to potassium during copper plating, and It was found that phosphorus had to be contained. The presence of these elements causes cracks to be generated by grain boundary oxidation, and the cracks are easily propagated to the surface. Therefore, cracks are more stably generated by wire drawing. FIG. 2 shows the prior art,
It is a schematic diagram which shows the surface layer part cross section of the product after annealing, copper plating, and further finishing wire drawing. FIG. 2A shows the grain boundary oxidized portions 3 and 4 of the substrate 1 and the copper plating layer 2, and FIG.
The wire shown in (a) is finish-drawn and the crack 7 is extended from the grain boundary oxide layer 5 to the plating surface to reach the surface, and the finish wire is drawn in the relatively narrow grain boundary oxide layer 9. As a result, no crack is generated in the copper plating layer 2. Therefore, conventionally, as described above, no crack is generated on the surface of the copper plating in the narrow small grain boundary oxidized portion 4, and the required amount of the lubricant is uniformly applied to and held on the surface of the copper plating wire by strong annealing. A grain boundary oxide layer had to be generated. In that case, the adhesion of the plating was poor, and the feedability required for a welding wire and other required qualities could not be obtained.

[0006]

Further, the present invention can sufficiently contribute to the generation of cracks in the copper plating layer even at the grain boundaries where the degree of grain boundary oxidation of the wire surface layer is weak. And a predetermined amount of the liquid lubricant is held, thereby contributing to an improvement in wire feedability. The form of the cross section of the wire surface layer portion of the present invention will be described in detail with reference to the schematic diagram shown in FIG. FIG.
(A) shows a substrate 1 with grain boundary oxidized portions 3 and 4 and a copper plating layer 2
FIG. 1B is a cross section of a surface layer portion of a product obtained by finish-drawing the wire shown in FIG. 1A at a reduction rate of 3 to 20% per pass, and shows a grain boundary oxide layer 5 up to the plating surface. FIG. 6 is a schematic view showing a state in which cracks 7 and 8 are extended from the grain boundary oxidized portion to the copper plating portion 2 to reach the surface. FIG.
As shown in (b), even in the relatively narrow and small grain boundary oxide layer 6, it can be seen that the crack 8 propagates to the copper plating layer 2 by the finish drawing. As described above, in addition to the cracks based on the conventional grain boundary oxide layer, the plating layer 2 of the present invention also generates relatively small cracks from the grain boundary oxide portions 4 on the surface of the copper plating 2 and occupies the wire surface. The areas of the cracks 7 and 8 also become large, and the ability to hold the liquid lubricant becomes very uniform and large.
The lubricant necessary for improving the wire feedability can be applied uniformly and in a required amount. Thus, a large number of cracks 7,
What can be ensured in finish wire drawing without impairing the characteristics of plating is that the copper plating layer contains a predetermined amount of potassium, sodium, tin, or phosphorus.

Next, the composition and content of the copper plating layer and the method of crack generation in the plating layer will be described in detail. To contain potassium, sodium, tin, or phosphorus in copper plating, use a plating solution containing copper pyrophosphate or potassium pyrophosphate as a main component, and further containing at least one of sodium pyrophosphate and tin pyrophosphate. The copper pyrophosphate plating bath used is the most efficient and stable. Since tin is electrically deposited, it can be controlled. However, potassium and sodium are elements that enter by being taken in during plating and are difficult to control. Therefore, as shown in FIG. It was clarified that it can be adjusted by controlling the composition of the inside. Further, if this wire is drawn at a reduction rate of 3 to 20% per pass, the surface layer has a greater degree of deformation than the center of the wire, so that tensile stress can be efficiently applied to the surface layer. It is even easier to form cracks on the surface.

[0008] Further, the present invention will be described in detail.

[0009] The surface of the steel substrate has grain boundary oxidation by annealing and copper plating, contains potassium in the copper plating, contains one or more of sodium or tin, and has a potassium content A in the copper plating. : 100 to 6000 ppm,
Content of at least one of sodium or tin B: 100 to
4000 ppm and A + B is 160 to 9000
ppm, and 10 to 1000 pp phosphorus during copper plating
The reason for containing m will be described. Conventional technology is shown in FIG.
As shown in (a) and (b), when the surface has grain boundary oxidation, a tensile stress is added to the surface by wire drawing, and a crack is easily generated in the copper plating. In this case, since the plating adhesion is poor and cracks are generated, the portions where the grain boundary oxidation is weak and the width is narrow do not contribute to the formation of cracks. Therefore, by adding potassium, further sodium or tin in the copper plating layer, it is possible to contribute to the occurrence of cracks in the copper plating even in the places where the degree of grain boundary oxidation is weak. Grain boundary oxidation mainly consists of iron oxides FeO, Fe ₃ O ₄ , F
Although e ₂ O ₃ is the main, potassium during plating, sodium and tin are present, receiving the oxygen from the grain boundary oxidation unit by heat generation during drawing, the grain boundary oxidation unit (K, Na) O, K
Generates potassium-based minute oxides such as ₂ SnO ₃ .
Therefore, these oxides serve as starting points at the time of wire drawing to easily contribute to the formation of cracks. Since these oxides are easily formed even if the grain boundary oxidation is weak, they can contribute to the formation of cracks regardless of the degree of grain boundary oxidation, and as shown in FIG. Cracks form. Therefore, it is essential to contain potassium, and further, sodium or tin is required. K ₂ Fe ₄ O for potassium alone
₇ , potassium-iron-based oxides such as K ₆ Fe ₂ O ₆ are easily formed. However, these are more easily dispersed and uniformly generated on the surface than at the grain boundary oxidized portions, so that they are unlikely to be the starting points of cracks. Since cracking only occurs at a portion where the grain boundary oxidation width is large, potassium alone has no effect. The reason why the potassium content A is 100 to 6000 ppm is that if it is less than 100 ppm, the oxide forming ability is weak, and if it exceeds 6000 ppm, the oxide is liable to be formed other than at the grain boundary oxidized part, and the plating adhesion is easily lowered. The same applies to the case where the content B of one or more of sodium or tin is 100 to 4000 ppm. Since the oxide that contributes to the crack is a combination of potassium and sodium or tin, it is not sufficient to use only these single elements, and a total specified amount is also required at the same time. When investigating this, A + B was 16
If it is less than 0 ppm, a small amount of potassium-based oxides such as (K, Na) O and K ₂ SnO ₃ is not generated so much that it cannot contribute to crack generation, and if it exceeds 9000 ppm, plating adhesion is reduced, so that 160 to 9000 ppm And
In addition, plating has lattice defects during the deposition process, and phosphorus has a property of easily collecting in the defects. Phosphorus is an effective element for promoting crack propagation, because defects tend to crack propagation in processing. That is, cracks are easily formed by adding potassium, sodium and tin, and cracks are easily propagated by adding phosphorus, so that cracks can be effectively formed on the plating surface. Phosphorus is ineffective at less than 10 ppm in copper plating, and becomes brittle at more than 1000 ppm, further reducing the toughness of the weld metal.
Therefore, it was limited to 10 to 1000 ppm.

The reason that the wire surface has a crack crossing in the longitudinal direction and the liquid lubricant adheres to the surface is that the lubricant contained in the crack reduces the frictional resistance due to the contact with the wire surface in the conduit tube. And to improve the feedability. The reason that the crack crossing the longitudinal direction is good
This is because the lubricating ability can be maintained because it is difficult for the liquid lubricant to escape from the cracks when being fed in the conduit tube. The effect can be maintained even if the intersection is not necessarily 90 degrees with the longitudinal direction.

The reason why an aqueous solution containing copper pyrophosphate or potassium pyrophosphate as a main component and further containing at least one of sodium pyrophosphate and tin pyrophosphate for copper plating is as follows. Potassium, sodium, phosphorus, when contained in a large amount in the plating bath, when the metal is deposited,
It is taken in by plating particles and enters a trace amount. On the other hand, tin is an element that can be electrically deposited. The present inventor has paid attention to this point, and has found that a bath capable of incorporating potassium, sodium and phosphorus into the plating and further capable of electroplating tin is a pyrophosphate bath. The addition amount of these elements can be adjusted by the plating bath concentration, the temperature, the current density, and the flow rate of the plating solution.
Since A / dm ² and the temperature are almost fixed at about 50 ° C., it is easiest to change the concentration of the plating bath and the flow rate of the plating solution. Since potassium and sodium are difficult to electrodeposit, when sodium is contained as shown in FIG. 3, by adjusting the ratio of (potassium pyrophosphate + sodium pyrophosphate) / copper pyrophosphate in the copper pyrophosphate plating bath. Adjustable. Since tin can be electrodeposited in the same manner as copper, it can be adjusted by the metal concentration ratio in the bath.

The reason why the flow rate of the plating solution is 5 to 60 m / min is to control the phosphorus content. It is known that phosphorus is related to the flow rate of the plating solution, and should be adjusted to the range shown in FIG. When the flow rate is less than 5 m / min, the phosphorus content is less than 10 ppm.
The liquid flow rate was limited to 5 to 60 m / min since the amount exceeded 00 ppm and did not fall within the phosphorus content range of the present invention. As described above, by using an aqueous solution composed mainly of copper pyrophosphate and potassium pyrophosphate as well as one or more of sodium pyrophosphate and tin pyrophosphate, potassium, sodium, tin and phosphorus can be removed. Incorporation into copper plating becomes possible.

The reason why wire drawing is performed with a reduction rate of 3 to 20% per die is that a tensile stress is efficiently applied to the surface by wire drawing, thereby making it easier to generate cracks. When wire drawing is performed at a surface reduction rate of 3 to 20%, a tensile stress acts relatively more on the surface layer side than the center of the wire, and a crack is easily generated if there is a starting point. As described above, by adding one or more of sodium and tin in addition to potassium during copper plating, a fine oxide is generated in the grain boundary oxidized portion, so that a crack origin is formed, and by further adding phosphorus, Since cracks are easily propagated during plating, cracks can be efficiently and stably formed by adjusting the drawing reduction ratio. If it is less than 3%, the area reduction rate is too low and the number of dice passes increases, which is not suitable for industrial production. If it exceeds 20%, the degree of deformation of the surface layer becomes equal to that of the inside, and tensile stress does not act on the surface layer preferentially, so that efficient crack formation cannot be performed.

[0014]

Examples are shown below.

C 0.1%, Si 0.75%, Mn 1.5
%, Ti + Zr 0.25% component 5.5mm wire rod
Wire drawing to 3mm, annealing in nitrogen gas atmosphere 700 ~
After performing 750 ° C. × 3 to 5 hours, the thickness is 1 to 1.5 μm
Copper plating of 1.2mm by wet wire drawing
Finished. Electro copper plating is copper pyrophosphate plating,
Copper plating under standard conditions of copper cyanide plating and copper borofluoride plating was also performed for comparison. In the copper pyrophosphate plating bath, potassium pyrophosphate and copper pyrophosphate were mainly used, and when sodium was added, the amount of sodium pyrophosphate was changed as shown in FIG. 3 to adjust the content in the plating. p
H was unified to 8.8. Since tin can be deposited by electroplating, tin pyrophosphate was added according to the amount of deposition. The phosphorus content was adjusted by changing the flow rate during plating. In addition, the wet wire drawing was performed by using a diamond die having an approach angle of 12 degrees and changing the area reduction rate per die.

Regarding the state of occurrence of cracks in the copper plating layer,
Cracks intersecting the longitudinal direction of the surface of the 1.2 mm drawn wire were evaluated, and 「indicates“ present on the entire surface ”, ○ indicates“ about half present ”, and“ x ”indicates“ almost no ”.

As shown in FIG. 7, the wire feedability of the wire was evaluated by rotating a conduit tube 12 having a length of about 3 m to a diameter of about 200 mm at substantially the center and further fixing a radius of the welding torch 13 side to about 250 mm. The feed resistance in the conduit tube was evaluated based on the armature current value of the feed motor at the time of welding. Regarding the feeding property, 1 to 2 A was rated as good (◎), 2 to 3 A was rated as average (○), and 3 A or more was rated as poor (×).

The arc stability was determined by sensory evaluation when the above welding wire was fed to a welding torch and a steel sheet was continuously subjected to an arc to perform welding.良好: good, ○: normal, and x: poor.

Test results are shown in Tables 1-1, 1-2 and 1-3. [Test conditions] Wire diameter: 1.2 mm Welding conditions: 300 A, 32 V, 30 cm / min Wire protrusion length: 25 mm Shielding gas: CO ₂ 25 liter / min Steel plate: SM400, thickness 20 mm

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

In Comparative Examples 1, 3, and 7, potassium, sodium, and tin were less than 100 ppm in the copper plating, respectively, and the starting point of the crack was not sufficiently formed, and only a small crack was formed on the surface of the 1.2 mm drawn wire. The feedability and arc stability were average.

In Comparative Examples 2, 4, and 8, the amounts of potassium, sodium, and tin exceeded the predetermined amounts, and the starting points of cracks were formed too much, resulting in poor plating adhesion after 1.2 mm wire drawing and cracking. On the contrary, the feeding property and the stability of the arc became poor due to clogging of the plating tube peeled at the time of feeding in the conduit tube.

In Comparative Examples 5 and 9, potassium + sodium and potassium + sodium + tin were less than 160 ppm in the copper plating, and the starting point of the crack was not sufficiently formed, and only a slight crack was found on the surface of the 1.2 mm drawn wire. Because of the inability to do so, feedability and arc stability were average.

In Comparative Examples 6 and 10, potassium + sodium and potassium + sodium + tin were 9000 ppm, respectively.
And the starting point of the crack was formed too much and 1.2 mm
Adhesion of plating after wire drawing was poor, and although cracks could be formed, the plating peeled off during feeding was clogged in the conduit tube, and conversely the feeding properties and arc stability were poor.

In Comparative Example 11, phosphorus was less than 10 ppm, and cracks could not be sufficiently propagated in wire drawing.
Since only a few cracks were formed on the surface of the 2-mm drawn wire, the feedability and arc stability were average.

In Comparative Example 12, the phosphorus content was more than 1000 ppm, and the plating was brittle and the plating was peeled off after drawing 1.2 mm. Therefore, cracks were formed, but the plating clogged in the conduit tube at the time of feeding. Feedability and arc stability were poor.

In Comparative Example 13, the tensile stress was not preferentially applied to the surface layer because the one-pass area-reduction ratio exceeded 20%, and a crack could not be formed on the entire surface. The properties and arc stability were average.

In Comparative Examples 14 and 15, the element in the copper plating was only potassium, which did not contribute to the generation of cracks, did not allow sufficient cracks to be generated, and had good feedability and arc stability.

Comparative Examples 16 and 17 were copper cyanide,
In the case of copper plating using a copper borofluoride bath, copper cyanide cannot contribute to crack initiation when it contains only potassium as in Comparative Examples 14 and 15, and copper borofluoride is the starting point of cracks and the element that affects propagation is under plating. Cracks are formed in the wide grain boundary oxidized part, but not enough.
Arc stability was modest.

Compared to the above comparative examples, the examples of the present invention can generate cracks sufficiently, and the oil accumulates in the cracks to enhance the lubricating ability, so that the feeding property in the conduit tube is extremely good.

[0033]

The present invention can be implemented as described above.
There is a remarkable effect of solving the above-mentioned technical problem. In other words, according to the present invention, it is possible to remarkably improve the feedability of the steel wire for gas shielded arc welding in the conduit tube, and the industrial merit is great.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a cross section of a surface layer portion of a welding steel wire according to the present invention after copper plating (a) and a product (b).

FIG. 2 is a schematic diagram of a cross section of a surface layer portion of a conventional welding steel wire after copper plating (a) and a product (b).

FIG. 3 shows the relationship between the copper pyrophosphate plating bath composition and the total potassium + sodium content in copper pyrophosphate plating.

FIG. 4 shows the relationship between the phosphorus content in copper pyrophosphate plating and the plating solution flow rate during plating.

FIG. 5 is a photograph showing formation of a crevices on the surface of a product according to the present invention.

FIG. 6 is a photograph showing the formation of a crack on the surface of a conventional product.

FIG. 7 shows a schematic diagram of a wire feedability test.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Wire base 2 Copper plating part 3 Strong grain boundary oxidation (wide) 4 Weak grain boundary oxidation (narrow) 5 Crack-like crack of the product after finish drawing which occurred in strong grain boundary oxidation part 6 Weak grain boundary oxidation part Cracks in the product after finishing wire drawing occurred in the cracks 7 Cracks in the copper plating part (strong grain boundary oxidized part) 8 Cracks in the copper plating part (weak grain boundary oxidized part) 9 Does not develop into a turtle-shaped crack Weak grain boundary oxidation part 10 Feed motor 11 Wire spool 12 Conduit tube (about 3 m length) 13 Welding torch 14 Steel plate (SM400 20 mm thick) 15 Turntable 16 Arc

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Hitoshi Tashiro 23-15 Suzukocho, Kamaishi Nippon Steel Corporation Inside Kamaishi Works (72) Inventor Susumu Isozaki 3-5-4 Tsukiji, Chuo-ku, Tokyo Nippon Steel F-term (reference) in Welding Industry Co., Ltd. 4E084 AA09 AA14 BA22 CA25 CA38 DA10 HA01 4K023 AA04 AA19 BA12 CA09 DA11 4K024 AA09 AB01 AB19 BA02 BB27 BC03 CA01 CA02 CA10 DA10 DB07 GA14 GA16

Claims (3)

[Claims] 1. A steel wire for gas shielded arc welding, comprising a grain boundary oxide layer by annealing and copper plating on the surface of a steel substrate, wherein the copper plating contains potassium and at least one of sodium and tin. And potassium content A in the copper plating: 100 to 6000 ppm, content of at least one of sodium or tin B: 100 to 4
000 ppm, and A + B is 160-9000p
pm, and 10 to 1000 ppm of phosphorus during copper plating
A steel wire for gas shielded arc welding, comprising: a copper plating having cracks intersecting in a longitudinal direction of the wire, and a liquid lubricant adhered to a surface of the wire. 2. A method for producing a steel wire for gas shielded arc welding, comprising the steps of:
m, and a grain boundary oxide layer is formed on the surface by annealing. Subsequently, the annealed wire is made of copper pyrophosphate, potassium pyrophosphate as a main component, and sodium pyrophosphate and tin pyrophosphate. The copper plating wire is electroplated using an aqueous solution containing at least one or more seeds, and the copper plating wire is drawn with a reduction in area of 3 to 20% per die. Of manufacturing steel wire for gas shielded arc welding. 3. The method for producing a steel wire for gas shielded arc welding according to claim 2, wherein the flow rate of the plating solution is 5 to 60 m / min.