JPH032599B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of manufacturing a flux-cored wire by applying lubricating oil to a steel strip, bending it in the width direction using forming rolls, and filling the cavity with flux. The present invention relates to a method for manufacturing a flux-cored wire that has good properties, can improve forming speed, and can economically obtain weld metal of good quality. Fig. 1 is a schematic explanatory diagram showing general manufacturing equipment and processes for flux-cored wire, and Figs. 2 A to F are cross-sectional shapes in the width direction of the steel strip H at points A to F shown in Fig. 1. FIG. In the above manufacturing equipment, a steel band winding spool 1, a degreasing device 2, a steel band bending section 7, and a wire drawing machine 6 are arranged in order from the upstream side along the flow direction of the steel band H (direction of arrow a). The band steel curve forming section 7 is constructed by combining a forming roll 3, a feeding roll 4, and a holding roll 5, which rotate in the directions of the arrows. That is, the steel strip H unwound from the steel strip winding spool 1 enters the degreasing device 2, and is degreased and cleaned while passing therethrough. Next, the steel strip H enters the steel strip curve forming section 7, and is sent to the wire drawing machine 6 side by the feed roll 4 and holding roll 5, and is shaped into a flat plate by the forming roll 3.
The flux FL is sequentially deformed from the shape shown in FIG. A to the curved shape shown in FIGS. Then, the steel strip (rough wire) Ha with a circular cross-sectional shape (Fig. 2 E) is sent to the wire drawing machine 6, where the rough wire is drawn.
After being drawn as a flux-cored wire W having a diameter smaller than Ha, it is wound up. When bending the steel strip H using the forming roll 3 in the above procedure, assuming that no forming lubricating oil (hereinafter simply referred to as lubricating oil) is used, the surface of the steel or forming roll will become rough. In order to avoid this, the molding speed has to be reduced, resulting in a decrease in productivity and a rise in production costs. Therefore, attempts have been made to improve the slippage between the steel strip H and the forming rolls 3 by applying lubricating oil to the steel strip H, thereby increasing the forming speed. However, in the conventional manufacturing process, careful consideration was not paid to the conditions for applying lubricating oil (i.e., lubricating oil was applied to the entire surface of the steel strip using an extremely rudimentary concept and method). Lubricating oil was attached and remained on the inner surface of the steel strip Ha, and this remained in the product wire W. Therefore, when welding is performed using this wire, diffusible hydrogen remains in the weld metal due to the lubricating oil, resulting in welding defects such as pits and microcracks. Steel strip curved into a tubular shape
The lubricating oil that remains on the outer surface of the Ha is decomposed and vaporized when the wire is heated during welding, and is dissipated from the outer surface of the wire, so it is thought that the effect on the weld metal is extremely small. Therefore, in the conventional method of applying lubricating oil to the entire surface of the steel strip, consideration has been given to heating the rough wire Ha to several hundred degrees to gasify and remove the lubricating oil remaining inside the rough wire Ha. However, in this case, heating equipment and thermal energy are required, which inevitably increases production costs. Concerned about the above-mentioned situation, the present inventors have proceeded with studies on a method of obtaining high-quality welding wire without increasing production costs, and in particular have proceeded with studies on the conditions for applying lubricant. In other words, the cause of welding defects is that lubricating oil adheres to the inside of the rough wire Ha (on the cavity Q side), so if measures are taken to prevent lubricating oil from being applied to the inside, no lubricating oil will remain. I thought about it. In particular, the inner surface of the rough wire Ha originally has a small contact area with the forming roll for regulating the inner surface, and the relative slippage between the forming roll and the rough wire is also small, so even if this application is omitted, the lubrication performance will not deteriorate and high forming will occur. It was thought that the speed could be maintained. Therefore, using a lubricating oil applicator as shown in Fig. 3, oil-impregnated material (for example, sponge, etc.) 8
The lubricating oil L is supplied to both ends of the steel strip H to moisten the oil-impregnated material 8, and the lower surface of the steel strip H (the side corresponding to the outer circumferential surface of the product wire)
A flux-cored wire was manufactured by applying lubricating oil L to the wire (however, no heat treatment was performed). This should have resulted in good results as lubricating oil would not be applied to the inner circumference of the wire, but when welding was performed using the flux-cored wire manufactured in this way, contrary to expectations, welding defects occurred. There has occurred. Therefore, we conducted further research to investigate the cause of this problem, and found that even when the coating was applied only to the lower surface of the steel strip H, at the stage of bending the steel strip H with the forming roll 3, it was found that ) was found to be squeezed by the forming rolls 3 toward the end surface of the steel strip H. Therefore, when the curved steel strips H are butted together to form a tubular shape, the squeezed lubricating oil may penetrate into the butted portion, and some of it may even penetrate into the inside of the rough wire Ha, resulting in the infiltration. It was concluded that welding defects may be caused by lubricating oil, etc. The above inference is also based on the fact that pits and microcracks occur in the seam weld when the butt parts of the strip steel are welded and sealed (the above reasoning that lubricating oil infiltrates the butt part and this causes the occurrence of pits). I was confident. The present invention has been made in view of these circumstances, and it is an object of the present invention to provide a method for producing a flux-cored wire that can economically produce a welding wire that is free from welding defects. be. The method of the present invention, which achieves the above object, has a method of applying the method of the present invention to the surface of the steel strip, which is the outer circumference side of the product wire, at any point up to the initial bending stage of the steel strip, leaving the vicinity of both ends in the width direction, and extending the surface to the center side. The gist is that only lubricating oil is applied. That is, in the present invention, lubricating oil is applied only to the center side of the steel strip surface, which is the outer peripheral surface side of the product wire, leaving the vicinity of both ends in the width direction. It corresponds to a portion C on the lower surface side of the steel H excluding both ends E. It is desirable that the width of such non-applied portion E be large in order to completely prevent lubricating oil from penetrating into the forming wire, but if the non-applied portion E is made too large, it will interfere with the band steel H during forming. The lubricity with the roll 3 is impaired, and the steel strip and forming roll are likely to become rough. In order to prevent this, it is necessary to reduce the molding speed, which in turn reduces productivity. Therefore, in order to prevent the occurrence of welding defects without significantly reducing productivity, it is desirable to make the width of the non-applied area as small as possible to the extent that the above-mentioned purpose of preventing infiltration of lubricating oil can be achieved. However, it is recommended to ensure at least 0.5mm. Next, since the lubricating oil is used to improve the lubricity between the steel strip H and the forming rolls 3, the lubricating oil is applied to the surface of the steel strip before it is introduced into the steel strip curve forming section 7. However, the amount of deformation of the strip steel at the initial stage of bending [for example,
Since the amount of deformation shown in FIG. On the other hand, as the forming progresses, the lubricating oil applied to the surface of the steel strip is squeezed toward the ends in the width direction of the steel strip, and as the thickness of the oil film decreases, it becomes easier for the oil film to break partially, so the amount of lubricant applied is not constant. Assuming that, the further downstream the coating point is, the less likely it is that the final forming roll will run out of oil, giving a more favorable result. Under these circumstances, the lubricating oil may be applied at any point up to the initial bending stage of the steel strip, but it is preferable to apply the lubricating oil at a relatively later stage of the initial bending stage, since this can prevent the occurrence of oil film depletion. Incidentally, as a specific method of applying oil when carrying out the present invention, for example, the method shown in FIGS. 4 and 5 can be mentioned. That is, FIG. 4 is a cross-sectional explanatory view showing an embodiment in which lubricating oil L is applied to a steel strip H that has not yet been bent. When the steel strip H is run in the direction penetrating the page while applying the narrow oil-impregnated material 8,
The lubricating oil L can be applied only to the center side of the lower surface of the steel band H, leaving the vicinity of both ends in the width direction. FIG. 5 is a cross-sectional explanatory view showing an embodiment in which lubricating oil L is applied to the steel strip H at the end of the initial bending stage, in which the curved steel strip H is pressed against the oil-impregnated material 8 by the presser roll 5 and the strip is rolled. When H is run in the direction penetrating the plane of the paper, the lubricating oil L can be applied only to the center side of the lower surface (convex surface) of the curved steel strip H, leaving the vicinity of both ends in the width direction. The present invention is configured as described above, and can obtain the effects summarized below. (1) Since lubricating oil is not applied to the vicinity of both ends in the width direction of the steel strip surface, which is the outer peripheral surface of the product wire, lubricating oil may seep into the butt part of the strip or inside the rough wire during bending. There isn't. Therefore, when the obtained wire is used, welding can be performed without generating welding defects. (2) Since lubricating oil is applied to the main part of the steel strip surface that will be in contact with the forming rolls before the initial bending stage, a good lubrication condition can be obtained, and the production speed can be sufficiently increased. Can be done. This allows the production cost of the wire to be reduced. (3) The lubricating oil removal (baking) process can be omitted. Examples of the present invention will be described below. Example Steel strip with a thickness of 0.8 mm and a width of 14 mm (JIS-G-3141,
When manufacturing flux-cored wire using SPCE), lubricating oil was applied only to the center side of the steel strip surface, which is the outer circumferential side of the product wire, leaving a portion up to 1 mm from both ends in the width direction (applied amount: 0.5 g). / ^m2 ).
This was curved and a flux having the following composition was charged into the cavity and drawn to obtain a flux-cored wire (straight line 1.2 mmφ, flux rate 14%). Flux composition (wt%) TiO ₂ : 36 SiO ₂ : 7 Fe-Mn: 19 Fe-Si: 10 CaCo ₃ : 3 Iron powder: 20 CaF ₂ : 5 Total 100 Comparative example 1 Band on the outer peripheral side of the product wire A flux-cored wire was produced in the same manner as in the example, except that lubricating oil was applied to the entire surface of the steel (coating amount: 0.5 g/m ² ), and no heat treatment was performed to vaporize and dissipate the lubricating oil. Comparative Example 2 A flux-cored wire was manufactured in the same manner as in Example without applying any lubricating oil to the surface of the steel strip. When welding was performed using each of the above wires and the amount of hydrogen in the obtained wires was measured, the results shown in Table 1 were obtained.

[Table] As shown in Table 1, in Comparative Example 1, the amount of hydrogen in the wire was as high as 50 ppm, which caused welding defects such as pits and microcracks. On the other hand, in the example, the amount of hydrogen is as low as in Comparative Example 2 (no lubricant applied at all), and not only does no welding defect occur at all, but the molding is performed without any problems at the same molding speed as Comparative Example 1. I was able to do that. However, in Comparative Example 2, no lubricating oil was applied, so the lubricity between the steel strip and the forming roll was poor, and the surfaces of the steel band and forming roll were severely roughened.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the manufacturing process of flux-cored wire, Fig. 2 A to F are cross-sectional views showing the cross-sectional shape of the steel strip in the width direction at A to F in Fig. 1, and Fig. 3 is an explanatory diagram showing the manufacturing process of flux-cored wire. FIGS. 4 and 5 are perspective explanatory views showing the oil applying method, and cross-sectional views showing the lubricating oil applying method according to the present invention. 1... Steel band winding spool, 2... Degreasing device, 3
... Forming roll, 4 ... Feeding roll, 5 ... Pressing roll, 6 ... Wire drawing machine, 7 ... Curving forming process, 8
...Oil-impregnated material, H...Strip steel, FL...Flux.

Claims (1)

[Claims] 1. When manufacturing a flux-cored wire by bending a steel strip in the width direction with forming rolls and filling it with flux, any desired temperature is applied to the surface of the steel strip, which is the outer circumferential side of the product wire, up to the initial bending stage of the steel strip. A method for manufacturing a flux-cored wire, characterized in that at the time of , lubricating oil is applied only to the center side, leaving the vicinity of both ends in the width direction.