JPH08999B2 - Electrolytic surface cleaning method for steel wire for welding - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for electrolytically surface-cleaning a steel wire coil after batch heat treatment in a welding wire manufacturing process.

[Conventional technology]

As shown in FIG. 4, the manufacturing process of the steel wire for welding includes rough drawing wire-winding, batch annealing, surface cleaning-plating-finish drawing wire-winding step. 10 is a supply stand for rewinding a bundle of wire rods rolled to a desired diameter and supplying it to the wire drawing step.
Although not shown, the wire drawing process includes a descaler, a cleaning tank, a drying device, a rough wire drawing machine, and the like. The wire rod (steel wire) that has been roughly drawn is wound on a steel bobbin 12, a predetermined number of these bobbins are stacked, a bell-shaped inner cover and an outer cover are covered, and batch annealing is performed to prevent distortion caused by wire drawing. except.
After that, a steel wire is unwound from the bobbin, subjected to pretreatment, plated with copper, dried, finished drawn, and then wound.

[Problems to be solved by the invention]

In the batch type annealing described above, a predetermined number of bobbins, that is, wire coils are installed in the inner cover, a non-oxidizing atmosphere gas (for example, N ₂ ) is supplied into the inner cover, and heating is performed from the outside of the inner cover (electrothermal heater). , Radiant tube, open flame burner, etc.) to anneal the wire coil. Although the wire coil is heated by convective heat transfer and radiant heat transfer by the atmospheric gas circulating and convection, the degree of annealing differs between the inner peripheral portion and the outer peripheral portion of the wire coil due to the difference in position. In this case, the outer peripheral portion (wire) is better annealed than the inner peripheral portion (wire), and as a result, the thickness of the oxide layer of the wire surface layer produced by annealing is larger in the outer peripheral portion than in the inner peripheral portion. This oxide layer adhered to the wire surface, or was generated by the reaction of oxygen from H ₂ O present in the furnace with the alloying elements such as silicon, manganese, and titanium in the steel wire.
Fe ₂ SiO _4, FeMnO _2, iron oxides hard intergranular oxidation layer and the wire surface made of oxide such as TiO ₂ of _{(FeO, Fe 3 O 4,} Fe 2 O 3 , etc.) consisting of an external oxide layer two It has multiple layers. Of these, the external oxide layer deteriorates the plating adhesion on the surface of the steel wire, while the grain boundary oxide layer is essential for forming a hexagonal groove on the wire surface that provides good wire feeding performance as a steel wire for welding. In the subsequent electrolytic surface cleaning treatment step of the pre-plating treatment step, the external oxide layer is removed and the thickness of the grain boundary oxide layer is adjusted so that the hexagonal groove can be formed well in the final finish wire drawing step. Plate and finish wire drawing (Japanese Patent Laid-Open No. 62-57798).

However, as described above, despite the difference in the thickness of the oxide layer between the outer peripheral portion (wire) and the inner peripheral portion (wire) of the wire coil after annealing, the processing conditions of the conventional electrolytic surface cleaning treatment step are Since the same condition was applied from the outer circumference to the inner circumference, there was a difference in the thickness of the oxide layer (grain boundary oxidation layer) on the surface of the wire after the treatment. Therefore, the product wire manufactured from a single coil Quality (wire feeding performance, etc.) was uneven.

That is, the state of formation of the hexagonal groove of the wire portion of the product corresponding to the outer peripheral portion (wire) and the inner peripheral portion (wire) of the wire coil is large and small, respectively, and the wire feedability is good, respectively.
It becomes defective. In addition, since the outer boundary of the wire coil has a deep grain boundary oxide layer (hard and low elongation), peeling of the surface material is likely to occur during the finish wire drawing in parallel with the formation of the hexagonal groove, and the wire is fed as a product wire. There is a drawback that the surface material is easily peeled off by bending during feeding.

INDUSTRIAL APPLICABILITY According to the present invention, a steel wire coil after heat treatment having a different oxide layer thickness in the outer peripheral portion of the coil is subjected to electrolytic surface cleaning treatment by changing the treatment degree according to the surface state, and thus a welding steel having a uniform surface quality is obtained. It is an object of the present invention to provide an electrolytic surface cleaning method capable of obtaining a wire.

[Means for solving problems]

Where the gist of the present invention to achieve the above object is a method of continuously rewinding a steel wire coil that has been batch-type heat treated in a non-oxidizing gas atmosphere to perform electrolytic surface cleaning treatment on a steel wire, This is a method of electrolytic surface cleaning treatment of a welding steel wire in which the degree of electrolytic treatment is made to correspond to the remaining amount of untreated wire in a single coil and gradually reduced.

[Operation] In the present invention, the thickness of the oxide layer, particularly the grain boundary oxide layer, formed on the surface material of the steel wire subjected to the batch type heat treatment in the coil (bobbin winding or bobbinless winding) is determined from the outer peripheral portion (wire) of the wire coil. Since the thickness gradually decreases toward the inner circumference (wire), the degree of electrolytic treatment is also correspondingly reduced and the thickness of the grain boundary oxide layer of the steel wire surface base material after treatment is made uniform, The quality variation of the product wire due to the difference in the thickness of the grain boundary oxide layer was eliminated. As for the degree of electrolytic treatment, if the state of the treatment liquid (type, concentration, temperature, etc.) is determined, the current density D, treatment time T (T = L / V, L:
Processing length, V: wire speed). That is, the degree of treatment and D, T, L, V have a relation of electrolytic degree ∞D · T = D · L / V, and one of D, L, V, for example, the current density D is changed to adjust the degree of treatment. To do.

The atmosphere gas for the batch heat treatment uses a non-oxidizing gas because it is necessary to satisfactorily form a grain boundary oxide layer on the steel wire and suppress the formation of an external oxide layer. It is desirable to use nitrogen in consideration of running cost and safety when using an inert gas such as argon or a neutral or reducing gas such as nitrogen or CO as the non-oxidizing gas.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

The manufacturing process of the steel wire for welding is similar to that of FIG. 4 in the present invention as well, but differs from the conventional one in that the processing degree is gradually changed in the electrolytic surface cleaning process. That is, the original wire diameter is 5.5 m
A hot-rolled steel wire having mφ, chemical components C: 0.08%, Si: 0.84%, and Mn: 0.20% was used as a raw wire to manufacture a welding steel wire with a product diameter of 1.2 mmφ through the steps shown in Table 1. First, after reducing the diameter to 2.2 mmφ in the rough wire drawing process, the steel wire is bobbin wound into a coil body with a weight of 1000 kg, and in the next batch annealing process, a predetermined number of stacks (for example, 3 stacks) are installed inside the inner cover,
Annealing is performed in an N ² gas atmosphere. An oxide layer is formed on the surface layer of the steel wire after the heat treatment. As described above, the thickness of the oxide layer is different between the outer peripheral wire and the inner peripheral wire of the coil, and tends to be thicker in the outer peripheral wire.

1 (a), (b), (c) and (d) are the wire positions (horizontal axis, (1000 kg: coil outermost position, 0 kg : (Innermost circumference position of coil)), oxide layer thickness (left vertical axis), and electrolytic surface cleaning current density (right vertical axis). (A) shows (b), (c) after annealing. ) Shows the figure after the electrolytic surface cleaning process of the present invention example and the conventional example, respectively. In the figure, A is a grain boundary oxide layer,
B indicates an outer oxide layer, and D ₁ and D ₂ indicate current densities of the present invention example and the conventional example, respectively. Also, (d) is (a), (b),
The wire position of (c) is illustrated, and the wire coil 1c wound around the bobbin 12 is shown corresponding to the wire position (horizontal axis). Explaining the oxide layer thickness with reference to FIG. 1A, a grain boundary oxide layer is formed on the wire surface layer after batch annealing, and an external oxide layer is formed on the outer surface thereof. The grain boundary oxide layer A is the thinnest wire of the coil at the innermost circumference of about 5 μm, and becomes thicker toward the outer circumference and thickest at the outermost circumference of about 20 μm. The outer oxide layer B is seen from the wire position of about 200 kg, becomes thicker toward the outer circumference, and forms about 2 μm at the outermost circumference. The outer oxide layer B deteriorates the adhesion of the plating, and the grain boundary oxide layer A is an essential layer for forming a hexagonal groove on the surface of the product wire. However, since the formation state of the turtle groove is almost proportional to the thickness of the intergranular oxide layer, it is necessary to make the thickness uniform to eliminate the variation in the formation state of the turtle groove. That is, in the electrolytic surface cleaning step following the batch annealing step, the degree of electrolytic treatment is changed in accordance with the thickness of the oxide layer to completely remove the external oxide layer and make the thickness of the grain boundary oxide layer uniform. FIG. 2 is a view showing an electrolytic surface cleaning treatment apparatus used in the example of the present invention, and Table 2 shows treatment conditions when this apparatus is used. The degree of treatment is adjusted by changing the current density D in the present invention. The treatment method is electrolytic cleaning by an indirect power supply method, in which a plurality of tubular electrodes whose both ends are open are arranged in a non-contact state in the series direction by changing their polarities and passed through the electrolytic treatment liquid present in the electrodes. In this way, the wire is passed through the tubular electrode, and indirect power supply is performed while the electrode and the wire are kept in a non-contact state. (Publication of Japanese Laid-Open Patent Publication No. 57-140899 and Japanese Laid-Open Publication No. 53-116232) When the wire is an anode, the steel base of the wire melts violently, so the surface becomes smooth and the wire surface is highly cleaned. .
On the other hand, when the wire is the cathode, the steel base material is not melted, and the cleaning effect of the wire surface base material and the oxide layer, which is promoted mainly by chemical degreasing, cannot be expected very much. Therefore, by arranging the electrodes alternately with the positive and negative electrodes, the cleaning effect can be optimized and an appropriate surface texture can be obtained.

As shown in FIG. 2, tubular electrodes 5 whose both ends are open are arranged in series and in a non-contact state with different polarities.
Sulfuric acid 4 as the electrolytic treatment liquid flows from the liquid inlet 2 to fill the inside thereof, and then is discharged from the exhaust liquid outlet 3 to be sequentially repeated and refluxed.

The wire 1 to be processed penetrates through the central portion of each electrode 5 and is first processed by indirect power supply, and then the processing is sequentially repeated.

The degree of electrolytic treatment is adjusted by changing the electrode density, which is performed by changing the voltage of the power source 6. That gradually decreasing in correspondence with the coil within the position of the processing in the wire current density from 800A / dm ² to 200A / dm ^2. In this case, the coil body weight of 1000 kg is divided into 5 and the current density is set to 1 for every 200 kg of treatment.
Decrease by 50A / dm ² . The switching of the current density was performed when 200 kg passage time = 100 minutes had elapsed. Of course, the switching frequency may be increased, or the rotation meter 7 may be provided to directly correspond to the processing weight to continuously reduce the current density.

FIG. 1 (b) shows the thickness of the grain boundary oxide layer (A) in this case. The thickness of the grain boundary oxide layer is almost averaged and is about 5 μm. FIG. 1 (c) shows a case of a conventional example for comparison, in which the current density was set to 500 A / dm ² constant from the outer circumference to the inner circumference of the coil. At this time, the grain boundary oxide layer thickness was 0 μm for the innermost coil wire and for the outermost wire.
The difference is as large as 10 μm, and the variation in the thickness of the grain boundary oxide layer of the wire after annealing (FIG. 1 (a)) is maintained as it is.

As described above, in the present invention, the variation in the thickness of the grain boundary oxide layer on the wire surface generated in the batch annealing step is eliminated by changing the treatment degree in the electrolytic surface cleaning treatment step to obtain a uniform thickness. Then, in the subsequent plating step, the wire is copper-plated, and after a finish wire drawing step, it is wound as a product wire on a bobbin or the like.

Explaining the formation process of the hexagonal groove on the wire surface, the triple layer structure of the plated layer with a soft and stretched outer periphery after the plating process, the hard grain boundary oxide layer in the middle part, and the softened and stretched steel base inside A steel wire exhibiting a wire cross section of Next, when the steel wire is drawn in the finish drawing process, cracks are generated in the grain boundary oxide layer having a small elongation in the circumferential direction of the wire, and a hexagonal groove is formed.

A liquid lubricant such as oil, mineral oil, or a lubricant for wet wire drawing is applied to the surface of the welding steel wire for wire feeding and rust resistance, but this lubricant is retained in the hexagonal groove on the wire surface. To be done. Since the surface of the wire is in a microscopic oil-impregnated state, the wire lubricating ability is extremely good and the contact resistance with the conduit liner is reduced. As a result, the feeding resistance itself is low, the fluctuation range is narrowed, and the feeding performance is stable. The arc is stable due to the stable and uniform wire feeding, and welding defects such as uneven bead shape and defective fusion do not occur. Furthermore, since the liquid lubricant is held in a stable state in the hexagonal groove, stable feedability of the liquid lubricant can be obtained with the minimum amount of adhesion, and excess welding causes welding defects such as pits and blowholes. No welding occurs and excellent welding workability is achieved.

FIGS. 3 (a), (b), and (c) are drawing-substitute micrographs (× 100) showing the generation state of the hexagonal groove of the product wire, and (a) is an example of the present invention showing a coil body. A uniform and good hexagonal groove is formed in all the wire portions, and the above effect is evenly distributed over all the wire portions of the same coil body. On the other hand, (b) and (c) are according to the conventional example, (b) is the inner peripheral portion of the coil body, (c)
Indicates a tortoise shell groove formed in the wire portion on the outer peripheral portion. As is clear from this, the tortoise shell groove is hardly generated in (b) and the above effect cannot be expected, and in (c), the tortoise shell groove is remarkable. In other words, the steel wire for welding has different feeding performance in the longitudinal part of the wire obtained from the same coil body and quality control is difficult. Further, in the outer peripheral wire (c) in which the hexagonal groove is remarkably formed, the surface material is easily peeled off as described above, and in any case, the conventional manufacturing method has many drawbacks. The present invention has no such inconvenience.

〔The invention's effect〕

Since the present invention is configured as described above, it has the following effects. A steel wire coil that has been heat-treated in a batch process in a non-oxidizing gas atmosphere has an intergranular oxide layer on the wire base.The thickness of the wire wound around the innermost circumference of the coil is the thinnest, and the wire becomes thicker toward the outer circumference. It tends to be thickest on the outer circumference. On the other hand, as a characteristic that the welding steel wire should have, there is a feeding performance, and the performance is determined by the quality of the formation state of the hexagonal groove on the wire surface.

There is a close relationship between the thickness of the grain boundary oxide layer and the quality of the formation of the hexagonal groove, and the thicker the grain boundary oxide layer, the more remarkable the formation of the hexagonal groove. Therefore, it is necessary to make the thickness of the grain boundary oxidation layer of the steel wire after the batch type heat treatment uniform in all the wire portions of the coil body. In the present invention, the grain boundary oxidation is performed by applying the above electrolytic surface cleaning treatment method. A uniform layer thickness was achieved.
As a result, it is possible to obtain a good quality welding steel wire having a uniform wire surface property and no variation in feeding performance.

[Brief description of drawings]

(A), (b) and (c) of FIG. 1 are diagrams showing the relationship between the wire position in the coil and the oxide layer thickness and current density.
(A) is after annealing, (b) and (c) are examples of the present invention,
The figure after the electrolytic surface cleaning process of a prior art example is shown. FIG. 3D is a diagram showing a wire coil wound around a bobbin, FIG. 2 is a diagram showing an electrolytic surface cleaning treatment device, and FIGS. 3A and 3B.
(C) is a photomicrograph (× 100) of the metal structure showing the formation state of the hexagonal groove on the surface of the product wire, and (a) is according to the example of the present invention. (B) and (c) are based on a conventional example.
FIG. 4 is a diagram showing a manufacturing process of a welding steel wire.

Claims (1)

[Claims] 1. A method for continuously rewinding a steel wire coil that has been subjected to a batch heat treatment in a non-oxidizing gas atmosphere to perform electrolytic surface cleaning treatment on the steel wire, wherein the electrolytic treatment degree is a single coil untreated wire. A method for electrolytically cleaning a surface of a steel wire for welding, which is characterized by gradually reducing the amount of the residual steel according to the remaining amount.