JPS621551B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for coating wire rods. Conventionally, when applying paint to a wire, an excessive amount of paint is applied to the wire in advance, and then the paint is squeezed out to a predetermined thickness. In this case, the paint can be squeezed out by pulling up the wire rod with excess paint applied vertically and squeezing out the paint by gravity without using a squeezing device, or by running the wire horizontally and squeezing it out with upper and lower rollers. There are methods such as running the wire horizontally and drawing it with a die block with a U-shaped groove, using felt drawing or rubber plate drawing, and pulling the wire vertically and drawing it with a drawing die that has a die hole with a circular cross section. be. However, in the first method of gravity falling, it takes a long time to squeeze out the paint, making it impossible to increase the moving speed of the wire, and contacting guide rollers etc. after coating and before baking is completed. This causes the paint to peel off, making it necessary to install the baking furnace vertically, which increases equipment costs. In addition, in the method of squeezing with the second upper and lower rollers or the method of squeezing with the third U-shaped grooved die block, the wire diameter is 1.0 mm.
It is difficult to uniformly apply paint to such thick wire rods. The fourth method using felt drawing or rubber plate drawing lacks stability during long hours of work. Furthermore, in the method using a die with a fifth round hole, it is difficult to center the wire and the die hole correctly, and if the wire becomes eccentric and comes into contact with the peripheral wall of the die hole, paint will not adhere to this part. There are drawbacks. Therefore, as an improvement to this fifth method, using a plurality of dice,
A method has been considered in which the material is passed through the first die and then coated with paint again before being passed through the next die, but this method has the problem of poor workability. In view of these circumstances, the present invention is advantageous in terms of equipment costs and work efficiency compared to the method of vertically pulling the wire from a plating bath. This horizontal running type improves the uniformity of the paint layer thickness, which was an issue with conventional methods of this type, and improves the quality of the coated wire, and also improves workability by eliminating the need to repeatedly pass it through a die. The object of the present invention is to provide a method for coating wire rods that can improve the quality of the coating. That is, the present invention provides a method for guiding wire rods that contacts the inner circumferential surface of the wire rod after excessive coating is applied to the wire rod surface by dipping, spraying, pouring, or other coating operations while the wire rod is running horizontally. By passing the wire through a paint drawing die in which a large number of convex portions and concave portions for storing paint separated from the wire are arranged alternately in the circumferential direction, and the concave portions are formed with a radius of curvature of 0.3 mm or less, the wire can be A fixed amount of paint is uniformly distributed and applied over the entire surface of the wire due to surface tension. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an outline of the entire painting operation including pre-treatment and post-treatment. In the figure, a wire rod 1 led out from a wire rod supply means 2 is sent to a paint application section 5 through a pretreatment device 3 that performs degreasing and chemical conversion treatment and a drying device 4. In the paint application section 5, an excessive amount of paint 54 is applied to the wire 1 by a device comprising, for example, a paint storage tank 51, a circulation pump 52, a spray nozzle 53, and the like. Next, this wire rod 1 is passed through a paint squeezing die 6, and the excess paint 54 is removed by the die 6. After passing through the die 6, the wire 1 is sent to a baking furnace 7 to bake the paint adhering to the surface of the wire, and after passing through a cooling device 8, it is wound up by a winder 9. Note that the application means in the paint application section 5 is not limited to the above example, and any conventionally known means such as dipping, spraying, pouring, etc. can be employed. Further, in the example shown in FIG. 1, the paint is applied while the wire rod 1 is running horizontally, but as shown in FIG. After being immersed, it may be pulled upward, passed through a die 6, and then sent to a vertically arranged baking furnace (not shown). The paint drawing die 6 is shown in FIGS. 3 and 4.
As shown in the figure, a die hole 61 through which the wire 1 is inserted
The inner peripheral surface thereof has a shape in which a large number of wire guide convex portions 62 that contact the wire rod 1 and paint storage recesses 63 that are spaced apart from the wire rod 1 are arranged alternately in the circumferential direction. The convex portions 62 and concave portions 63 are each formed into an arcuate cross-section with a constant radius of curvature r ₁ , r ₂ , and the top of each convex portion 62 is connected to the wire rod 1 to be processed.
The recess 63 is recessed outward from the circumference by approximately its radius of curvature _r2 . Then, for reasons to be described later, the recess 63
The radius of curvature _r2 is 0.3 mm or less. Note that the front end of the die hole 61 is desirably tapered with an appropriate approach angle to facilitate the introduction of the wire rod 1 and the introduction of the paint. Then, the inner circumferential surface of the parallel portion behind the tapered portion 61a may have the above-mentioned uneven cross-sectional shape. The wire rod 1 with excessive paint attached is passed through the die 6.
By passing it through, the protrusions 62 on the inner circumferential surface thereof come into contact with the wire 1, thereby regulating the passing position of the wire 1, and a certain amount of paint is stored in each recess 63. Since a large number of the recesses 63 are arranged at equal intervals throughout the circumferential direction, it is possible to prevent the paint from being biased to one side of the wire 1. Immediately after the wire rod 1 passes through the die 6, the paint 54 adheres to the surface of the wire rod 1 in a shape corresponding to the inner peripheral surface of the die 6 as shown in FIG. Due to the tension, the paint 54 is attached to the wire 1 as shown in FIG. 5b.
The paint layer is evenly distributed over the surface and has a uniform thickness. In this method, by changing the cross-sectional shape of the die 6, that is, the size of the unevenness (radius of curvature) on its inner peripheral surface, and changing the gap area between the wire rod 1 and the die 6, the amount of paint stored in this gap can be changed. Since the amount also varies, the thickness of the paint layer can be adjusted.
That is, the thickness and uniformity of the paint layer depend on the cross-sectional shape of the die 6 and are almost unrelated to the length of the die 6 and the moving speed of the wire 1. Therefore, it can be effectively applied to high-speed work. Next, a specific example of this method and the results of an experiment using it will be shown. When baking a hardening polyester paint onto a steel wire with a diameter of 2.0 mm, the thickness of the paint layer after baking was measured by changing the uneven shape of the inner peripheral surface of the die 6, as shown in Figure 6. It looked like a graph. As for the die 6, the radius of curvature r ₁ of the convex portion 62 is
The radius of curvature r ₂ of the recess 63 is 0.13 mm and 0.20 at 0.35 mm.
mm, 0.25 mm, and 0.30 mm, these are ordinary wire drawing cemented carbide dies with irregularities formed on the inner circumferential surface by electric discharge machining, and due to machining accuracy, ±1/100 mm. The tolerance was too high. As shown in this graph, when the size of the recess 63 (radius of curvature r ₂ ) is changed, the thickness of the paint layer changes approximately in proportion to the size (radius of curvature r 2 ). In this case, if the thickness of the paint layer after baking exceeds 20μ, defects such as so-called wrinkles and bumps will occur on the surface, so
The radius of curvature r ₂ of No. 3 is preferably 0.3 mm or less. In addition, in this specific example, the radius of curvature r ₁ of the convex portion 62
is assumed to be constant, but the thickness of the paint layer can also be changed by changing this in various ways. In addition, in order to examine the uniformity of the thickness of the paint layer in each case shown as the above specific example,
The thickness of the paint layer on wire rod 1 after baking was measured at eight different locations in the circumferential direction using a betascope.
The table became as shown below. In the table, r ₂ is the radius of curvature of the recess 63, t min and t max are the average, minimum and maximum values of the thickness of the paint layer, and R is the variation in the thickness of the paint layer (t max - t min ).

[Table] As shown in this table, the variation R was sufficiently small compared to the thickness of the paint layer, and the uniformity was good. In addition, when examining the coating condition when coating and drawing were performed using a conventional paint drawing die with a die hole having a circular cross section, it was found that the diameter of the die hole was 2.01 mm and 2.02 mm for a steel wire with a diameter of 2.0 mm. In all cases, no paint was applied to the contact area between the steel wire and the inner peripheral surface of the die, making it impossible to measure the thickness. Further, when examining conventional commercially available coated steel wires, it was found that when the average thickness of the paint layer was 17 microns, the variation was about 6 to 7 microns. As described above, the present invention uses a paint drawing die in which a large number of convex portions that contact the wire rod and concave portions that are spaced apart from the wire rod are arranged alternately in the circumferential direction on the inner peripheral surface, and while the wire rod is running in the horizontal direction. By passing the wire with excessive paint applied through the die, the paint is prevented from adhering eccentrically to the wire, and after passing through the die, the paint is spread over the entire die surface due to surface tension. . For this reason, while basically adopting the method of horizontal movement, which is advantageous in terms of workability and equipment costs compared to the method of moving the wire vertically, the above-mentioned die increases the uniformity of the thickness of the paint layer. In particular, minute irregularities with a radius of curvature of 0.3 mm or less are formed on the inner circumferential surface of the die, making it possible to adjust the thickness of the paint layer with high precision.
It is possible to prevent so-called wrinkles and bumps from occurring on the surface of the coating film, and improve the quality of the coated wire. Furthermore, it is possible to perform high-speed work and improve workability.

[Brief explanation of the drawing]

Fig. 1 is an overall schematic diagram of the painting process using the method of the present invention, Fig. 2 is a partial schematic diagram showing another example of the adhesion and squeezing portion of the paint, and Fig. 3 is the paint squeezing die used in the present invention. FIG. 4 is an enlarged sectional view of the same part, FIGS. 5 a and b are partial sectional views showing changes in the paint adhesion state of the wire after passing through the die,
The figure is a graph showing the relationship between the shape of the inner peripheral surface of the die and the thickness of the paint layer after baking. 1...Wire rod, 5...Paint attachment part, 6...Dice, 61
...Dice hole, 62...Convex part, 63...Concave part.

Claims (1)

[Claims] 1. After applying paint excessively to the surface of the wire by dipping, spraying, pouring, etc. while running the wire in a horizontal direction, apply paint from the wire guide protrusion that comes into contact with the wire on the inner peripheral surface and from the wire. By passing the wire through a paint drawing die in which a large number of spaced apart paint storage recesses are arranged alternately in the circumferential direction and the recesses are formed with a radius of curvature of 0.3 mm or less, a predetermined amount of paint is applied to the surface after passing through the die. A method for coating a wire rod, characterized in that the coating is uniformly distributed over the entire surface of the wire rod under tension.