Flux Cored Welding Wire Manufacturing

Flux Cored Welding Wire Manufacturing

EPA1 - Method of production of welding wire

FIELD OF THE INVENTION

• The present invention relates to a method for production of welding wires of small diameters such as solid wires and cored wires ensuring particular smooth feeding to welding torches through conduit tubes during welding operation.

BACKGROUND ART

• Conventionally in welding like CO2 gas shielded arc welding and MIG welding, solid wires and cored wires of small diameters such as 0.8 to 1.6 mm are used. Solid wires are homogeneous through the diameter and cored wires are filled with fluxes and others in the core of steel tube shell, then also called flux cored wires. These welding wires are provided in spools or, for requirement of continuous supply of long wires, in pail packs. In usual welding operation, a wire feeding machine set near to the spool and or the pail pack produces a driving force on wires, and then feeds out wires through a conduit tube as far as to the electrode tip in a welding torch at the position of welding. The wire feeding machine is composed of a wire-feeding roller driven by a motor and a free-rotating pinch roller to grip and press the wire between the wire-feeding roller. At the central part of the conduit tube which contacts the wire, a liner made by spiral steel wires is provided for flexible guide for the wire.

• Though the conduit tube is usually in a length of 3 to 6 m, for welding of wide areas a tube as long as 20 m is required; the length of conduit tube is selected in accordance with distance to the welding position. By proper choice of the long conduit tube, welding operation can be easily conducted by moving only a light-weight welding torch even in a narrow space and a high or low place such as in the field welding for ship building.

• On the other hand, the long conduit tube has a problem to increase a resistance in feeding of welding wires. Wires are pushed into the liner inside of the conduit tube by a driving force of the feeding machine, and are subjected to the resistance in feeding due to friction in contact with the inside wall of liner. Although for a straight conduit tube high feeding forces are not required, for a conduit tube with a small radius of curvature or with a number of deflection positions, the resistance to feeding is large especially when the tube is long. In order to perform stable welding operation without occurrence of defects, it is necessary to feed the welding wire at a predetermined constant speed to the welding spot, that is, good feeding performance. However, if the resistance to feeding is high, the balance with driving force of feeding machine is difficult to be kept, leading to bad feeding performance.

• Application of some lubricants is necessary to reduce the feeding resistance of wires through the conduit tubes. For this purpose solid lubricants such as MoS2 are applied to the liner of the conduit tube. However, since the effects are not satisfactory, application of additional lubricants like oil on the surface of wires is necessary. The application of oil on wires could be made in the neighborhood of wire feeding machine, however, accurate control of coating amount of oil requires excessive burden of welding operators; it is difficult in the actual welding operation. If the amount of oil is not enough, naturally satisfactory lubrication cannot be achieved resulting in bad welding performance. On the other hand if the amount of oil is excessive, slipping occurs between the wire and the wire-feeding roller leading to unstable wire feeding speed and also an increase in hydrogen content by pick-up in weld metal is anticipated. Besides, since the wire driven out of the feeding roller is subjected to compression, for prevention of buckling, the wire is lead into a guide tube connected to the conduit tube immediately after departure from the wire feeding roller. Thus application of oil on the wire must be done before the entry into the feeding roller and the problem of slipping is inevitable.

• Accordingly, makers of welding wires are requested to supply wires with an adequate amount of lubricants and such wire products are available now. For instance, Japanese published patent No. Sho 50- discloses welding wires coated with lubricants on smooth and fine surfaces. However, uniform coating of a given amount of lubricants on the smooth surfaces was revealed to be difficult. To overcome the difficulty and obtain wires with sufficient lubrication, amounts of coating lubricants should be increased, resulting in slipping of wire-feeding rollers and picking-up of hydrogen in the weld metal.

• As a countermeasure for the above difficulty a proposal was made to coat lubricants stably and uniformly along the longitudinal direction of wires by depositing lubricants on dents by increasing roughness of wire surfaces. For instance, Japanese published patent No. Hei 4- discloses a method of increasing roughness of wire surfaces by drawing wires after annealing in a particular atmosphere. The method is not usually applicable since the chemical compositions in wires must sufficiently include the elements having a stronger affinity for oxygen than iron, such as Ti, Si and Mn, at the annealing temperature.

• On the other hand, Japanese published patent No. Sho 58- discloses a method for obtaining rough surface by drawing wires through hole dies under forced lubrication by increased pressure on lubrication oils. Although the method decreases the flatness of wire surface, it can hardly obtain deep dents to retain lubricants. Therefore, improvement of feeding performance is not expected if a coating amount of lubricants on the surfaces is not higher than 2.0 grams per 10 kilograms of wire. Other methods proposed for increasing the surface roughness such as laser irradiation, shot blasting, and embossing by cemented carbide rolls with uneven surfaces are not practically applicable because of problems of high costs in equipment and operation.

DISCLOSURE OF THE INVENTION

• The present invention is intended to provide a method for producing wires which have rough surfaces necessary to retain lubricants by modifying the process of reduction of diameter in sequence from raw wires to welding wires. Application of lubricants on the surfaces of wires produced by the present method permits satisfactory feeding of welding wires without lack of lubricants even in severe operation conditions.

• The present method for production of welding wires through drawing of raw wires is characterized by comprising steps of dry hole die drawing with application of powder lubricants, roller dies drawing by such as cassette-type roller dies, and wet hole die drawing, at least in a part of a sequence of wire drawing processes. Furthermore a succeeding step of drawing by hole dies with application of lubrication oil may be conducted to make the wire to a product diameter.

• In the present method the wires prior to the dry hole die drawing have surface roughness of preferably at least 0.3 µm in terms of Ra along a longitudinal direction of wires.

• Furthermore, the welding wires produced by the present invention are either sold wires or cored wires and have surface roughness Ra of preferably at least 0.08 µm along a longitudinal direction of wires.

BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a schematic diagram representing an example of equipment for carrying out the present invention, FIG. 2 is a schematic diagram of cassette-type roller dies, and FIG. 3 is a schematic diagram of an apparatus used for testing wire feeding performance. FIG. 4 is a scanning electron micrograph of a surface of a welding wire produced by the present invention and FIG. 5 is a scanning electron micrograph of a surface of a welding wire produced by a comparison method.
BEST MODE FOR CARRYING OUT THE INVENTION

• In the method for production of welding wires by drawing from raw wires to smaller diameters, the present invention differs from the conventional methods at least in a part at the later stage of drawing. The raw wires for production of solid wires are hot-rolled wires of 10mm or so in diameter produced by wire rod mills. Besides, the raw wires for production of cored wires are tubes in which filler materials such as fluxes are filled by supplying from one end of long tubes of 10 mm or so in diameter with application of vibration, otherwise, tubes which are made by steel bands continuously bent by rolls into U shape, filled with filler materials, further formed into a cylindrical shape and welded at the seam. Besides, in the present invention the cored wire is not limited to the closed-seam type, but also includes a open-seam type with folded-in seam.

• Although drawing into welding wires is sometimes executed continuously in a single stage, explanation will be made for the case of separate two-stage drawing of roughing and finishing. In manufacturing of solid wires, starting wire rods are pickled to remove oxide scale formed at high temperatures in hot rolling, lubrication films such as phosphate are formed on them, and transferred into roughing process. In the roughing process wires are reduced in diameter by passing continuously through a series of hole dies under dry lubrication with lubricants containing mainly metal soap. In the roughing process some of the hole dies can be replaced by roller dies which pass the wire through a pair of free rotating rollers. Roller dies drawing permits a high reduction in a draft, while a large reduction in hole die drawing needs a high drawing force tending to lead in fracture of wires.

• Because the drawn wires after roughing into as much as several times of the final diameter are work hardened, they are softened by annealing to facilitate the latter drawing process. Subsequently the surfaces are cleansed and plated with copper, then the wires are transferred to further drawing processes. In the above process copper plating may not be applied for stainless steel wires and annealing may be omitted for some usage of welding wires. In the finishing process while wires are continuously drawn into the final diameter through a series of hole dies, drawing is performed usually under wet lubrication by immersing the hole dies in emulsion oil or spraying emulsion oil to the hole dies. For prevention of buckling while feeding in welding operation, welding wires should have sufficient strength and rigidity; so work hardening during the finish drawing can give this property.

• In the above process for production of welding wires, roughing drawing is sometimes executed in multiple stages separated by intermediate annealing for softening. The annealing may be executed as batch in a form of coil in furnaces or continuously by passing through a furnace. And another modification is a combination of continuous annealing and copper plating in a line. Details in processes can be different in accordance with production factories. In the above the production method of solid wires are mentioned. In the production of cored wires, since drawing just after filling of filler material may leads to nonuniform distribution of them, cold rolling before roughing drawing is executed by groove rolls to be dense enough for prevention of movement of the filler material. The subsequent process is the same as the process for solid wires.

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  Hereupon, the present invention comprises steps of dry hole die drawing with application of powder lubricants, subsequent roller dies drawing and subsequent wet hole die drawing, at least in apart of the sequence of the above mentioned wire drawing processes for production of welding wires, in place of conventional drawing solely by hole dies. Through these processes, welding wires of good feeding performance can be produced by forming roughness enough for deposition of lubricants on the surfaces of welding wires.

• The finishing wire-drawing process of the present invention represents the processing after the dry hole die drawing in the sequence of wire drawing. By operation of the above mentioned three types of drawing processes at least in a part of a sequence of the wire drawing processes in particular in the final process or just prior to the final process, the effects of the present invention can be attained. Therefore no particular specification is made for roughing process in the present invention, and also, any additional drawing process into the finishing process represents no departure from the present invention, although such necessity is not usually found. Furthermore, as will be mentioned later, finish drawing through hole dies with a small reduction into a final diameter can be carried out by application of lubrication oil.

• The welding wires produced in accordance with the present invention are provided with a good feeding performance being coated with both of solid lubricants and lubrication oil. The purpose of the present invention is to provide welding wires which are coated these lubricants uniformly and stably on the surface of wires. The solid lubricants to be used are one or two kinds of MoS2 and WS2. In the following description the solid lubricants and the lubrication oil to be applied on welding wire product are distinguished from the lubricants for drawing by describing as solid lubricants for feeding and lubrication oil for feeding respectively. Details of the present invention will be explained in the following.

• FIG. 1 shows a schematic diagram of an example of equipment for executing the present invention. In this example the starting material of wire 11 is coiled in a supply reel 12. The starting wire is an intermediate product of solid wires or cored wires of about 2 to 5 mm in diameter with or without copper plating and is desired to have a surface roughness at least 0.3 µm in terms of the Ra value defined by JIS B- in the profile along a longitudinal direction of wire. This means that some degree of roughness on the surface of starting material is desirable to effectively achieve the effects of the present invention for formation of the required roughness in the final products. These rough surfaces can be produced mostly by drawing through hole dies under dry lubrication at the last stage of roughing, or sometimes by drawing through roller dies with rough surfaces produced by shot blasting. Furthermore rough surfaces can be produced by chemical etching with controlling the conditions for pickling prior to the copper plating. Besides, the roughness Ra represents an average of the absolute derivation values from the central of a measured roughness curve; Ra is used in the same manner in the standards of many nations as Japanese industrial standards (JIS). The surface roughness described in the present invention represents values measured as roughness curves along a longitudinal direction of wires if not particularly mentioned otherwise.

• To begin with, dry hole die drawing as the first process of the present invention is performed through hole dies 13 by use of powder lubricants containing solid lubricants for feeding without use of liquid lubricants. 31 in Fig. 1 represents a capstan exerting a force to pull wire; the wire is wound repeatedly on the cylinder driven for rotation. 32 and 33 in the another place are also capstans having the same function. Powder lubricants are strongly inlayed on the surface of drawn wire by the drawing through the hole dies 13. Therefore, the original surface roughness is kept and the powder lubricants are retained in the dents on the wire surfaces. As the hole dies 13 for dry hole die drawing, use of rotary dies is favorable in order to maintain their holes exactly circular.

• In the subsequent roller dies drawing, cassette type roller dies 21, 22, 23 and 24 are employed in the example shown in FIG. 1. FIG. 2 shows a schematic diagram of one of the above four cassette-type roller dies. As shown in the figure, small diameter rollers 41 to 50 having a groove with a profile to match the size of wire 51 to be drawn are arranged in each pair such as 41 and 42, 43 and 44, 45 and 46 to form a unit of roller dies. These roller dies are arranged at a near position so that the rotating axes are set alternately to be oriented in perpendicular direction as shown in FIG. 2 for five pairs. These pairs of roller dies are called a cassette-type roller dies since the units are compactly combined into a block as a whole. Drawing through the roller dies is executed without further use of lubricants and wires are reduced in diameter in sequence. Because the powder lubricants inlayed on the wire surfaces by the dry hole die drawing resist collapse of the dents, decrease in roughness is minimized. In other words in contrast to the conventional hole die drawing which occurs much slip between wire surfaces and dies, the roller dies drawing retains much of the powder lubricants on the wire surfaces with little stripping off of them.

• The wires reduced to a given diameter through the roller dies drawing are further drawn into a product size of 1 to 2 mm diameter by wet hole die drawing. The wet hole die drawing-equipment 14 is composed of multistage slip-type drawing machine with a multiple of hole dies 15 immersed in a bath containing lubricant oil. The speed of wet hole die drawing reaches as high as m per minute. The wet drawing has effects for removal of excessive lubricants and stains and for making wire cross-section accurate circle. During the drawing passes through a multiple of hole dies in the wet drawing process, the dents on the wire surface are gradually flattened and then the powder lubricants on the wire surfaces are reduced. Therefore in the process of wet hole die drawing, area reduction must be kept within an amount enough to retain necessary roughness and lubricants satisfactory for feeding performance for use as welding wires. Thus by designing an optimum allotment of area reduction between dry hole die drawing, roller dies drawing and wet hole die drawing, necessary amount of roughness and adhered lubricants are ensured. In the example in FIG. 1, finishing drawing after the wet hole die drawing is further executed into a given product size by using hole dies 16 with application of lubrication oil. For the purpose of product size adjustment and others such an additional drawing without significant reduction in surface roughness after the wet hole die drawing represents no deviation from the scope of the present invention. 17 in FIG. 1 is a take-up reel for coiling of the welding wires produced in the sequence of drawing processes.

• Thus the present invention aims to decrease an amount of reduction in wet hole die drawing by replacing the hole die drawing with roller dies drawing, where in conventional processes hole die drawing is exclusively adopted in the finishing drawing process. By this process powder lubricants are dented on the wire surfaces during the dry hole die drawing and the dented rough surfaces are retained in the following process of the roller dies drawing due to the compressive deformation mode of the roller dies drawing. In the next process of the wet hole die drawing the powder lubricants in the dents tend to be discharged without further supply, then the dents get smaller and shallower. Therefore by limiting an amount of reduction in the wet hole die drawing necessary roughness is guaranteed for satisfactory performance as welding wire products.

• The favorable roughness on the surfaces of welding wires ensuring good feeding performance is at least 0.08 µm in terms of Ra along the longitudinal profile. The desirable amount of adhered lubricants for feeding as a sum of the amount of solid lubricants for feeding and lubrication oil for feeding is at least 0.3 g for a wire of 10 kg weight. The solid lubricants for feeding which might be any of MoS2, WS2 or a mixture of MoS2 and WS2 as mentioned before, are desirably applied at least 0.1 g for a wire of 10 kg weight. MoS2 and WS2 have effects of decreasing friction between inner walls of conduit tube liners and wires, and of suppressing increase in feeding resistance. Solid lubricants for feeding are adhered on the wire surfaces by mixing at least 10% of powder lubricants in the above mentioned dry hole die drawing process.

• The lubrication oil for feeding which might be any of animal fats, vegetable oils, mineral oils or synthetic oils is desirably adhered at least 0.2 g for a wire of 10 kg weight. The lubrication oil supplements the lubrication by solid lubricants retained in the dents on wire surfaces. As explained with FIG. 1, the lubrication oil for feeding can be adhered on the product surfaces by using as lubrication oil for wire drawing in the finishing wire-drawing process through the hole dies 16. Another way is to apply on the wire surfaces in the recoiling process of coiled wires.

EXAMPLES

• In the following the present invention will be explained by referring examples. Starting wires were prepared by drawing in roughing process down to 3.3 mm diameter, annealing and copper plating. By following the process shown in FIG. 1, welding wires of 1.4 mm diameter were made in a product form of spool coils. Types of welding wire products were flux cored wires (JIS Z YFW-C50DR, packing ratio of flux: 15%) and solid wires (JIS Z YGW11). Examination was made for surface morphology and performance in feeding of the wire products. Roughness of the starting wires along the longitudinal direction profile were 0.7 µm and 1.5 µm.

• The dry hole die drawing was executed to 20% in area reduction using hole dies of a rotary type. The used powder lubricants were composed of a mixture of graphite, PTFE, potassium soap, titanium oxide, talc, wax and others; and of MoS2 and/or WS2 as lubricants for feeding which were added to the mixture to be a portion of 30 and 50% to the total.

• In the cassette-type roller dies drawing the wires were drawn to area reduction of 40 and 70% without lubrication.

• No. type of wire sureface roughness of staring wires Ra (µm) kind and amount of lubricants for feeding in powder lubricants (%) drawing schedule dry hole dies roller dies wet hole dies diameter finished (mm) area reduction (%) diameter finished (mm) area reduction (%) area reduction (%) 1 F 0.7 MoS2 40 3.04 15.1 1.70 68.7 32.2 2 F 0.7 MoS2 40 2.95 20.1 1.70 66.8 32.2 3 F 0.7 MoS2 40 2.86 24.9 1.70 64.7 32.2 4 F 0.7 MoS2 30 2.95 20.1 2.20 44.4 59.5 5 F 0.7 MoS2 40 2.95 20.1 2.20 44.4 59.5 6 F 0.7 MoS 2 50 2.95 20.1 2.20 44.4 59.5 7 F 1.5 MoS2 40 2.95 20.1 2.20 44.4 59.5 8 F 0.7 WS2 40 2.95 20.1 2.20 44.4 59.5 9 F 0.7 MoS2+WS2 40 2.95 20.1 2.20 44.4 59.5 10 S 0.7 MoS2 40 2.95 20.1 1.70 66.8 32.2 11 F 0.7 MoS2 30 2.95 20.1 - - 77.5 12 F 0.7 WS2 30 2.95 20.1 - - 77.5 13 S 0.7 WS2 30 2.95 20.1 - - 77.5 14 F 0.7 - - - - - 82.0 15 S 0.7 - - - - - 82.0

  In the wet hole die drawing the wires were drawn to total area reduction of 30 to 60% through five to ten dies in a drawing bath containing emulsion oil main components of which were synthetic oil and anion surfactant. Successively, drawing to the product diameter at the finishing dies (16 in FIG. 1) was carried out by using palm oil which acts also as lubricant for feeding.

• Table 1 shows the testing conditions; examples of No.1 to No.10 represent the conditions in accordance with the present invention. At the examples of No.1 to No.3 the area reduction in the dry hole die drawing was varied 15, 20 and 25% for a given content 40% of MoS2 in the powder lubricants. At the examples No.4 to No.6 the contents of MoS2 in the powder lubricants were varied 30, 40 and 50% at a given area reduction of 20% in the dry hole die drawing. The diameters of wires after the roller dies drawing were 1.70 mm (area reductions: 65 to 69%) for the examples Nos.1 to 3 and 2.20 mm(area reduction: 44%) for Nos.4 to 6. The example No.7 is the case for changing No.5 with the surface roughness of starting wires, the example Nos.8 and 9 are respectively the cases for changing No.5 with the types of solid lubricants for feeding, and the example No.10 is the case changing the flux cored wires of No.2 with solid wires.

• Examples No.11 to No.15 represent comparisons not included in the present invention. Examples Nos.11 to 13 are the cases where the roller dies drawing was not conducted between the dry hole die drawing process and the wet hole die drawing process, consequently, the area reduction in the wet hole die drawing was large as 70% or more. Examples Nos.14 and 15 represent the conventional method process without dry hole die drawing and roller dies drawing.

• roughness Ra at least 0.10 µm amount of solid lubricants for feeding at least 0.10 g/ 10 kg wire amount of lubrication oil for feeding at least 0.10 g/ 10 kg wire resisting force to feeding at most 6.0 kgf slip ratio at most 10.0%

  For evaluation of the effects of the present invention in these tests, examination was made for surface condition and feeding performance of the test produced wires. As the surface condition, the roughness in terms of roughness Ra along the longitudinal profile of wires and the deposit amounts of solid lubricants and lubrication oil for feeding were examined. As the tests for feeding performance, resistance force to feeding and slip ratios of wires were evaluated according to the procedure as explained later. Then, if the measured values were in the ranges shown below, judgment was made to be satisfactory.

• The test of feeding performance of wires was conducted by the equipment a schematic diagram of which is shown in FIG. 3. The welding wire 62 coiled on a spool 73 was fed by the wire feeding machine 61 to the welding position 66 through the conduit tube 65. On the spot of welding 66 a steel plate 68 was set on a turn table 69, then, by using the welding wire fed out of the welding torch 67 connected with the conduit tube 65, bead-on-plate welding was carried out on the steel plate 68.

• The conduit tube 65 was 6 m long, and for giving a feeding resistance to wires, two rings 70 of 150 mm diameter were formed along the length of the conduit tube. Peripheral velocity Vγ (=preset velocity of wire feeding) of the feeding roller 64 in the wire feeding machine 61 was measured and also speed Vω of the wire was measured with the wire speed detector 72 in contact with the moving welding wire. Besides, 63 in FIG. 3 is a pinch roller. These measured values were sent to a computer not shown in the figure, then slip ratio SL was calculated as below. SL = (Vγ-Vω)/Vγ × 100

• The feeding resistance was detected by a load cell 71 connected to the mechanism of the feeding roller 64, as a reaction force upon the conduit tube caused by the welding wire. The feeding performance of the test wires was evaluated in terms of values of the resistance to feeding and the slip ratio as formerly mentioned.

• 2 gas as the shielding gas, 33V as the welding voltage, 300A as the welding current, 30cm/min as the welding speed, and 10 m/min as the feeding velocity of wire. No. surface condition wire feeding performance total evaluation roughness of product Ra (µm) lubricants for feeding (g per 10kg of wire) resistance to feeding (kgf) slip ratio (%) solid lubricants lubrication oil 1 0.18 0.66 0.64 2.4 5.5 good 2 0.17 0.54 0.53 2.5 5.3 good 3 0.17 0.67 0.55 2.3 5.6 good 4 0.12 0.20 0.49 3.3 3.0 good 5 0.13 0.24 0.56 3.5 3.5 good 6 0.13 0.30 0.54 3.4 4.3 good 7 0.19 0.73 0.63 2.1 6.9 good 8 0.12 0.18 0.57 3.2 3.2 good 9 0.12 0.21 0.71 3.3 3.5 good 10 0.17 0.53 0.82 2.5 5.7 good 11 0.08 0.06 0.51 6.7 11.1 slightly bad 12 0.08 0.05 0.48 7.2 13.8 slightly bad 13 0.08 0.07 0.52 6.8 12.7 slightly bad 14 0.06 0 0.56 8.9 30.5 bad 15 0.06 0 0.49 9.0 36.7 bad

  The welding conditions in the above feeding performance test were set to be COgas as the shielding gas, 33V as the welding voltage, 300A as the welding current, 30cm/min as the welding speed, and 10 m/min as the feeding velocity of wire.

• The test results are shown in table 2. The examples Nos. 1 to 10 in accordance with the present invention show low values of feeding resistance in a range of 2 to 4 kgf and slip ratio 3 to 7%, then give stable welding arc because of excellent feeding performance. Among them the examples Nos. 1, 2, 3 and 10 give higher contents of lubricants for feeding than the examples No.4,5,6,8 and 9, because of higher product roughness that is caused by smaller area reductions in wet hole die drawing as a result of smaller wire diameters at the finishing of roller dies drawing. Therefore the examples Nos.1, 2, 3 and 10 show lower resistance to feeding and a little higher slip ratio within the good performance range. In the example No.7 the surface roughness of the starting wire Ra is as high as 1.5 µm, then the surface roughness of the product wire is high and a rather higher amount of lubricants is retained, resulting in a rather higher slip ratio than the example No.5.

• The examples for comparison Nos.11 to 13 give a surface roughness as low as 0.08 µm and the lubricant content is rather small; consequently show higher resistance to feeding and higher slip ratio than the examples Nos.1 to 10 of the present invention, resulting in bad feeding performance. The examples Nos.14 and 15 have surface roughness lower than 0.08 µ m and have not adhered solid lubricants for feeding; consequently have higher resistance to feeding and higher slip ratio, leading to failure in welding because of unstable arc due to bad feeding performance.

• FIG. 6 and FIG. 7 show scanning electron micrographs of the surfaces of the products manufactured under the conditions No.2 and No.11. The surface in FIG. 6 is sufficiently rough for the welding wire product by the present invention and the surface in FIG. 7 is rather smooth for the product by the method for comparison.

APPLICATION TO INDUSTRIES

• The present invention provides with low cost satisfactory rough surfaces on welding wires necessary for retention of lubricants, by use of dry hole die drawing and roller dies drawing in place of conventional processes using totally hole die drawing in the sequence of drawing to smaller diameters from starting wires into welding wires. By coating lubricants for feeding on these surfaces, welding wires can be supplied which ensure good feeding performance without occurrence of deterioration in lubrication even under severe operating conditions.

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