JPH046478B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical Field of the Invention) The present invention relates to a method for producing steel wire for fully automatic and semi-automatic welding using copper plating treatment with excellent feedability. (Conventional technology) Generally speaking, CO ₂ gas shield welding, MIG welding, etc.
Copper-plated welding steel wire with a diameter of 0.8 to 2.4 mm is used. These welding wires are usually used for welding while being wound around a spool or bobbin, or loaded into a cylindrical container called a pail pack. When these wires are used, they are installed in a feeder, which is an attached device to a welding machine, and welding is performed through a feeding roller, a flexible conduit tube extending 3 to 20 meters, a welding torch, and a contact tip. There are many examples. In addition, devices are used in which a wire spool is mounted on a traveling trolley and no conduit tube is used, but this device is more complex and larger than the installation type described above, and requires a welding area. There are drawbacks such as limitations, and its uses are limited. Now, there are three types of welding wire feeding systems using flexible conduit tubes: push type, pull type, and push-pull type, but the push type is used more frequently because it is easier to handle. However, the conduit tube of a push-type feeder is usually 3
When welding a wide area, a length of about 20 m is used, and at this time problems arise with wire feedability. Welding wire is required to be fed at a constant speed. However, the wire is subject to contact resistance with the liner, torch, and tip that are guide tubes of the flexible conduit, and resistance force due to passing through the bent portion of the flexible conduit tube. There is almost no on-site work where the flexible conduit tube is in a direct state, and it is usually used in a bent state, and the more bends there are and the smaller the bend radius, the greater the resistance to passing through the bends. The wire is pushed forward and fed by the force that overcomes the contact resistance force with the welding wire as described above, but as the contact resistance increases, the feeding speed of the welding wire becomes uneven and eventually In this case, a situation where the supply is stopped occurs. For this reason, the welding arc becomes unstable,
Various welding defects such as irregular bead shapes, poor fusion, and undercuts occur. Recently, as welding work has become more complex, faster, and wider, welding wires that have low frictional resistance with flexible conduit liners, can be fed smoothly and stably, and can always be fed at a constant speed have been developed. There has been a strong demand for welding wires with stable feedability. Conventionally, in order to improve the feeding performance of the wire, the feeding power of the feeder has been increased or the feeding performance of the wire itself has been improved. For example, in order to improve the feedability of the wire itself, as in the wire disclosed in Japanese Patent Publication No. 50-3256, liquid lubricant is applied to the surface of the wire, which has a sufficiently microscopically dense and smooth surface. Although methods are known for increasing the lubricating ability of the material and reducing the feeding resistance, it has not always been possible to obtain a method that shows stable feeding performance.
The reason for this is that because the wire surface is dense and smooth, it is difficult to apply liquid lubricant evenly and stably to the wire surface, and in order to achieve the desired performance, a large amount of lubricant must be applied. Because it was not profitable. Moreover, lubricating oil applied to the wire surface in an unnecessarily large amount only causes changes in the material of the welded part or adversely affects welding workability. Figure 1 is a metal micrograph (magnification x 400) showing the surface condition of a conventional wire with a dense and smooth surface.
It is. This conventional wire is annealed in the atmosphere, that is, in a state with a lot of oxygen, so it is several μm below the wire surface.
Iron oxides (FeO, Fe ₃ O ₄ ,
This produces an oxide film, the so-called external oxide layer, whose main component is Fe ₂ O ₃ , etc.). Since this external oxidation layer has a negative effect on the plating adhesion of the wire, it is removed in the next plating pretreatment (pickling), and the surface of the wire is cleaned, and plating such as copper plating is applied to the surface. . The steel wire at this time has a plating layer with elongation on the outer periphery, and a double structure wire cross section with elongation that has been softened and annealed on the inside. Since the plating layer stretches, a wire with a dense and smooth surface as shown in FIG. 1 is obtained. In addition, as disclosed in JP-A-54-141349, there is a method of forcibly pressurizing the surface of the wire to change the surface roughness and reduce the contact resistance, but this method is less effective than the above-mentioned lubricating oil. The effect is almost the same as that of improving feedability by coating, and is still not satisfactory. As a welding steel wire that overcomes the drawbacks of conventional wires, the present applicant has developed a wire disclosed in Japanese Patent Application Laid-open No. 144892/1983. That is, the original wire diameter 5
When manufacturing steel wire for welding using ~6mmφ hot-rolled steel wire, wire drawing is performed to remove stress from the wire that has been hardened by wire drawing in order to obtain the appropriate tensile strength that the product should have. Batch-type softening annealing is performed in an atmospheric gas midway through the process. For example, batch annealing is performed at 700°C for 4 hours in a nitrogen gas atmosphere. This annealing lowers the tensile strength of the steel wire to a predetermined level, and the surface layer of the steel wire is oxidized by moisture, lubricant, etc. that has adhered to the wire surface from the previous process and is brought into the annealing furnace. It becomes a hard internal oxidation layer with a thickness of several μm to 10 μm. Next, the upper layer of the wire surface that deteriorates plating adhesion is removed by pickling treatment in the plating pretreatment process, and the hard internal oxidation is removed so that hexagonal grooves are well formed in the final wire drawing process. After adjusting the layer thickness, plating such as copper plating is performed. In this way, a soft and stretchy plating layer is formed on the outer periphery,
A wire rod having a wire cross section with a triple structure is obtained, with a hard internal oxidation layer generated and adjusted by annealing in the middle portion and an elongated wire rod which has been softened and annealed in the inner portion. The thus-obtained thinned steel wire is drawn to a desired product diameter in a final wire drawing step. When the wire is drawn in the final wire drawing process, the adhesion between each layer is not impaired, and horizontal grooves are formed in the circumferential direction of the wire surface, starting from the thinnest and least elongated part of the intermediate internal oxidation layer whose thickness has been adjusted. It develops, and tortoiseshell-shaped grooves are formed on the wire surface. This manufacturing method is a so-called passive manufacturing method in which an internal oxidation layer is generated on the wire surface layer only by oxygen sources such as moisture and lubricant that have adhered to the wire surface in the previous process. For this reason, at least 2
This necessitated annealing for an extended period of time, making it difficult to carry out each process continuously. This is because the time required for each process such as wire drawing, plating pretreatment, and plating treatment is within a few minutes, and if annealing alone takes several hours, an extremely long annealing furnace would be required for continuous operation. This is because it must be installed. Therefore, a batch-type annealing furnace is conventionally used. FIG. 2 is a metallurgical micrograph (magnification x 400) showing the surface condition of this welding steel wire, and it can be seen that hexagonal-shaped horizontal grooves are formed on the wire surface. This lateral groove is a groove formed in the circumferential direction of the wire, and this groove exhibits a hexagonal pattern as a whole. With this wire, it is possible to deposit as little liquid lubricant as possible in a stable and uniform manner in the longitudinal direction of the wire. That is, the liquid lubricant is retained in the cracks on the wire surface, and the surface of the wire becomes microscopically oil-impregnated, so that the lubrication ability of the wire surface 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 wire feedability is stabilized. Stable and uniform wire feeding makes the arc stable, and welding defects such as irregular bead shapes and poor fusion do not occur. Furthermore, since the liquid lubricant is held in a stable state within the plating cracks, stable feeding performance can be achieved with a minimum amount of wire adhesion, resulting in welding defects such as pits and blowholes caused by excessive lubricant. Excellent welding workability is achieved. (Object of the Invention) The present invention is the most preferable method for manufacturing a welding wire having hexagonal grooves formed on the wire surface and having good feedability. It is an object of the present invention to provide a manufacturing method capable of obtaining a welding steel wire having a groove in the shape of a groove. Another object of the present invention is to provide a method of manufacturing steel wire for welding, which allows the manufacturing process to be continuous. (Structure and operation of the invention) The gist of the present invention to achieve this object is to mix an alkali metal carbonate into a powdered lubricant in a die box, and apply the alkali metal carbonate to the surface of a steel wire using a hole die or a roller die. A method for manufacturing a steel wire for welding, which comprises applying a metal carbonate under pressure, annealing in a non-oxidizing atmosphere, followed by plating and wire drawing. The present invention will be explained in detail below. In the present invention, an internal oxidation layer is generated in the wire by soft annealing in a non-oxidizing atmosphere. In order to reduce the amount of oxygen in the annealing furnace, it is possible to use an inert gas such as argon gas, or a so-called neutral or reducing gas such as nitrogen gas or a mixed gas of carbon monoxide and carbon dioxide, but this reduces the running cost. For example, nitrogen gas is used in consideration of safety and the like. In addition, in the present invention, in order to shorten the time required to generate an internal oxide layer on the wire, an alkali metal carbonate is pressure-coated on the wire before annealing, and then annealing is performed in an annealing furnace with the above atmosphere at a temperature of 650°C or higher for 1 minute. By holding the temperature above, a desired internal oxidation layer is generated. The reason why the alkali metal carbonate applied to the wire surface promotes the formation of an internal oxidation layer on the wire is explained using potassium carbonate as an example of an alkali metal carbonate.The potassium carbonate decomposes at a high temperature of 650°C or higher, It is thought that internal oxidation progresses in the wire surface layer due to the effect of the carbon dioxide gas generated as K ₂ CO ₃ →K ₂ O + CO ₂ effectively increasing the oxygen partial pressure in the atmosphere. Sources of oxygen supply are moisture adhering to the wire being annealed, wire drawing lubricant, or impurities in the atmosphere gas, and carbon dioxide gas generated by decomposition of alkali metal carbonates is a stable source of oxygen supply. Oxygen brought from these oxygen sources reacts at high temperatures with alloying elements such as silicon and manganese, which have a stronger affinity than iron in the steel wire, forming Fe ₂ SiO ₄ and FeMnO within approximately 10 μm from the wire surface. Generates an internal oxide layer consisting of oxides of grade ₂ . At this time, if annealing is performed in a nitrogen gas atmosphere, some nitrides and carbides inevitably generated by the nitrogen and carbon in the lubricant adhering to the wire will also be contained in the internal oxidation layer. Also, some iron oxides (FeO, Fe ₃ O ₄ ,
Fe ₂ O ₃ etc.) are also produced, but since there is very little oxygen in the furnace, the above-mentioned iron oxide film state, ie, external oxidation state, does not occur. In this way, an alkali metal carbonate is applied to the wire surface prior to wire annealing, and the application method is to mix the alkali metal carbonate with a powdered lubricant (for example, metal soap) in a die box (lubricant box). A pressure application method using a hole die or roller die is used. In this way, a hard internal oxide layer consisting of the above-mentioned oxides, nitrides, and carbides is formed within approximately 10 μm from the wire surface. Following the annealing process, the pickling process removes the upper surface layer such as iron oxides that are generated during annealing and impairs the adhesion, and also ensures that the tortoise-shell pattern grooves are well formed in the final wire drawing process. After adjusting the thickness of the hard internal oxide layer, plating (not essential) is performed. In this way, the wire rod has a wire cross section with a triple structure: a soft and elongated plating layer on the outer periphery, a hard internal oxidation layer generated and adjusted by annealing in the middle, and an elongated steel wire that has been softened and annealed inside. can get. When this triple-layered wire is drawn in the final wire drawing process, the adhesion between each layer is not impaired, and the hexagonal pattern grooves are formed around the circumference of the wire surface, starting from the point of least elongation in the hard intermediate layer. occurs in the direction. Here, preferred annealing conditions will be explained. In the present invention, the atmosphere inside the furnace is a non-oxidizing atmosphere,
In order to effectively generate an internal oxide layer on the wire, the atmosphere should have an oxygen content of 2 vol% or less, preferably 1 vol% or less. Further, as described above, when a steel wire coated with an alkali metal carbonate is annealed in a non-oxidizing atmosphere, it is necessary to maintain the annealing temperature at 650°C or higher for 1 minute or more. That is, the lower limit of the annealing temperature of 650°C is the temperature necessary to decompose the alkali metal carbonate. On the other hand, the upper limit is not particularly limited, but in consideration of energy costs, 900°C or less is desirable. As for the annealing time, keeping the steel wire at a temperature of 650° C. or higher for 1 minute or more is sufficient for the purpose of forming hexagonal pattern grooves. If the annealing temperature is maintained for more than 1 minute, the thickness of the internal oxidation layer will increase as the annealing time increases; however, since there is no adverse effect even if the internal oxidation layer becomes slightly thicker, the upper limit of the annealing time is The value is not particularly limited and may be appropriately determined based on energy costs and the like. The annealed wire thus heated at a predetermined temperature and for a predetermined time to form an internal oxidation layer and softened is cooled and supplied to the next step. A lubricant is applied to the surface of the produced steel wire for welding to improve wire feedability and rust resistance. These lubricants contain surfactants. The reason why the welding wire manufactured by the manufacturing method of the present invention has good feedability is that, as mentioned above, lubricant such as liquid lubricant during wire drawing enters the hexagonal cracks on the wire surface. The surface is in a micro-lubricated state, so when it comes into contact with the inner wall of the conduit liner during welding, the liquid lubricant present in the cracks is discharged, which reduces contact resistance and provides stability with less variation. This provides excellent feedability. Examples of the manufacturing method of the present invention will be described below. Original wire diameter 5.5mmφ, chemical composition C: 0.08%, Si: 0.80
%, Mn: 1.53% hot-rolled steel wire as the raw wire, welding steel wire of 1.2 mmφ from (a) to (c) in Table 1.
It was manufactured through the steps shown in the following. Manufacturing process (a)
is a process using potassium carbonate (K ₂ CO ₃ ),
Step (b) is a step using sodium carbonate (NaCO ₃ ), and step (c) is a step using lithium carbonate (Li ₂ CO ₃ ).

【table】

[Table] Figure 3 is a metallurgical micrograph (magnification x 400) showing the surface condition of the welding steel wire manufactured based on Table 1 (a). is formed on the wire surface. Although the wires in FIGS. 2 and 3 have tortoise-shell-shaped cracks formed on their surfaces, the time required for annealing is significantly different; in the case of the wire shown in FIG. According to the present invention, a very short softening annealing time is required to obtain a wire surface condition having hexagonal grooves. Therefore, in the present invention, it is possible to make the process continuous. FIG. 4 is a diagram showing the relationship between the amount of liquid lubricant adhering to the wire surface and the feeding resistance. The feedability was tested under the conditions shown in Table 2.

[Table] The wire feeding performance can be equivalently expressed by the feeding motor armature current, and the larger the armature current value, the greater the feeding resistance and poorer feeding performance. The smaller the value, the better the feedability. As is clear from the figure, the conventional wire C has a dense and smooth surface.
Wires with hexagonal cracks on the surface compared to
Both the wire A manufactured by the manufacturing method (a) of the present invention and the wire B manufactured by the conventional manufacturing method have low feeding resistance and good wire feeding performance. Note that the wire feedability according to the manufacturing methods (b) and (c) of the present invention shown in Table 1 was also good, as was the case with wire A. (Effects of the Invention) As described above, according to the present invention, a steel wire for welding having hexagonal grooves formed on the wire surface can be manufactured stably in a short time. Therefore, each process can be made continuous. The present invention, which exhibits such effects, is of great industrial benefit.

[Brief explanation of drawings]

Figures 1, 2, and 3 are metallurgical micrographs (magnification x 400) showing the surface condition of steel wire for welding. Fig. 3 shows a wire having cracks produced by the conventional manufacturing method, and Fig. 3 shows a wire produced by the manufacturing method (a) of the present invention. FIG. 4 is a diagram showing the relationship between the amount of liquid lubricant deposited and the feeding resistance. In Fig. 4: A: Wire with hexagonal cracks on the surface made by the method (a) of the present invention, B: Wire with hexagonal cracks on the surface made by the conventional method, C: Surface dense and smooth. conventional wire.

Claims (1)

[Claims] 1. Mix an alkali metal carbonate in a powdered lubricant in a die box, pressure apply the alkali metal carbonate onto the surface of a steel wire using a hole die or a roller die, and then anneal it in a non-oxidizing atmosphere.
A method for manufacturing a steel wire for welding, which comprises subsequently performing plating treatment and wire drawing.