JPS6315076B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a flux-cored wire for welding, and more particularly to a method for uniformly filling a tubular pipe with flux and manufacturing a homogeneous, high-performance flux-cored wire with high productivity. It is something.

Wires made of a metal sheath filled with welding flux are called flux-cored wires or composite wires.For example, there is no need to supply flux from the outside, so welding preparation is easy, and the wires have good porosity resistance. Suitable for on-site welding
Compared to using coated arc welding rods, it can be expected to be more than twice as efficient, has shallower penetration, and has better cracking resistance.
It is becoming popular mainly in the field of automatic or semi-automatic welding. However, the growth rate of consumption is stagnant, reaching only about 10% of solid wire consumption. The reason for this sluggish growth is
The problems include a large amount of fume, somewhat unstable wire feedability, easy absorption of moisture by the filling flux, low productivity and high cost. These problems are largely due to the poor flux sealing performance of the metal jacket. In other words, general flux-cored wire is manufactured by bending a steel band in the width direction, forming it into a tubular shape, filling it with flux, and then drawing it to a predetermined cross-sectional dimension. Since both ends of the steel strip are simply pressure-welded and lack sealing properties, moisture may infiltrate from these parts and moisten the flux, or the feeding resistance at the pressure-welded portion may become uneven and the flux may not be fed properly. It is believed that this leads to unstable speed and poor contact with the current-carrying chip, resulting in the problems described above.

As a measure to deal with such problems, for example, as seen in Japanese Patent Application Laid-Open No. 56-148494, the butt portions of both side edges obtained by bending a steel band in the width direction are sealed by seam welding. A method is known, and by using such a method, it is possible to obtain a flux-cored wire without the above-mentioned disadvantages. However, with this method, the heat input during seam welding causes the flux to deteriorate or burn out, so the type and properties of the filling flux are limited. In the high-frequency induction welding method, which can only achieve a welding speed of about 1/2 min and has extremely low productivity, an impeder must be inserted into a small diameter curved wire, which inhibits flux filling. Therefore, there are problems such as the fact that the flux filling rate in the longitudinal direction of the wire tends to be non-uniform.

On the other hand, for example, Japanese Patent Publication No. 45-30937 and
As seen in Publication No. 56-148494, one end of a seamless tubular wire is filled with flux and then drawn, and its surface is plated with a conductive material such as copper to make it conductive. Higher versions have also been proposed. With such a flux-cored wire, there is no seam in the steel outer shell, so there will be no deterioration or deterioration due to moisture absorption of the filling flux or welding heat. However, filling a small-diameter tubular wire with powder flux is itself extremely complicated, and it is extremely difficult to make the filling rate uniform over the entire length. Moreover, the conventional filling method, which utilizes the vibration of the tubular wire and the gravity flow of the flux, has an extremely slow filling speed and is inefficient, and it is often experienced that the tubular wire becomes clogged with flux, resulting in unfilled areas. .

The inventors of the present invention have focused on the above-mentioned circumstances, and have conducted research to establish a method that can uniformly fill flux into a tubular wire, particularly in the method of manufacturing flux-cored wire by filling flux into a tubular wire. We have been progressing. The present invention was completed as a result of such research, and involves running a metal wire in the longitudinal direction within a coating booth, and electrostatically coating the outer surface of the wire with a powdery flux composition containing a powdery adhesive. The gist is that the flux is then heated and fired, then inserted into a steel pipe and subjected to expansion and contraction processing.

The structure and effects of the present invention will be explained below based on the drawings showing the embodiments. However, the following are representative examples and do not limit the present invention, and only within the scope that can comply with the spirit of the above and below. Appropriate changes in the electrostatic coating method, heating annealing conditions, etc. are all within the technical scope of the present invention. FIG. 1 is a schematic process explanatory diagram showing an embodiment of the present invention, in which a wire W _-1 made of mild steel or the like (generally the same material as the tubular wire described later) is wound around a spool 1, and After sending it to the derusting/degreasing device 2 to clean the surface, it is sent to the drying device 3.
, and send it to electrostatic coating station 4. Here, the flux F is attached by an electrostatic dipping method or an electrostatic spraying method which will be described in detail later. The wire W _-2 coated with the flux F is sent to the heating and firing device 5, where the flux F that has simply adhered electrostatically is removed.
is fixed. A long tubular wire W _-3 is prepared at the rear of the heating and firing device 5, and a piano wire is attached to the wire W _-1 protruding from the tip of the flux-coated wire W _-2 that has been fired or cooled as necessary. 6 etc. and by pulling it, the painted wire W _-2 is inserted into the tubular wire W _-3 . It is effective that the length of the tubular wire W _-3 is as long as possible to insert the coated wire W _-2 against its insertion resistance.
In addition, in order to reduce the insertion resistance, painted wire
It is better to make the outer diameter of W _-2 slightly larger than the outer diameter of tubular wire W _-3 . Further, the wire W _-2 and the piano wire 6 can also be joined by welding.
The obtained flux-filled wire W _-4 is then sequentially passed through wire-drawing dies 7a and 7b to be wire-drawn to a predetermined size, and if necessary, subjected to copper plating or the like to form a product.

The principle of electrostatic coating is to charge powder using a DC high voltage obtained by an electrostatic generator, and make it adhere to a grounded object by electrostatic attraction. When carrying out the electrostatic coating in the present invention, an electrostatic dipping method and an electrostatic spraying method can be adopted, but these methods themselves can be carried out in accordance with methods already practiced in the field of electrostatic coating of powder coatings. For example, in the case of the electrostatic immersion method, there are special considerations regarding the capacity of the immersion tank, the material and shape of the bottom plate, the air feeding mechanism, the grounding method, the voltage, the wire supply mechanism, the wire gripping mechanism in the ground, etc. There are no restrictions. The flux powder may be charged either positively or negatively, but in view of convenience of operation and the problem of residual electrostatic voltage in subsequent steps, it is preferable to ground the wire and charge the flux negatively. Regarding the electrostatic coating of flux, each electrostatic coating means has its own problems, which will be explained below.

First, when implementing the electrostatic spraying method, it has the advantage that it is less affected by differences in the specific gravity of the flux composition and can be coated uniformly even if there is a slight difference in specific gravity. There are some problems in obtaining the coating thickness, especially when forming a thick coating film, the coating film becomes thinner in areas where the spray direction is tangential to the surface of the object to be coated, resulting in uneven coating, eccentricity, etc. Because defects tend to occur, it was necessary to use a device to rotate the metal wire, or to change the direction of the metal wire and apply multiple coats, but in any case, as the coating thickness increases, electrostatic repulsion due to flux increases. Therefore, it is recommended to improve the charging voltage or raise the temperature of the object to be coated.

Next, in the electrostatic dipping method, the flux powder placed on a porous plate is blown up by compressed air from below.
This is done by forming a primary fluidized bed of powder and applying a high voltage between the electrodes installed on the porous plate and the booth ceiling, and the wire connected to the ground wire. By arranging the wires, it is possible to paint relatively uniformly and thickly from the top, bottom, left and right. However, when various component powders are blown up at once, there is a problem in that the fluidized bed itself varies due to the difference in specific gravity of each powder, causing variations in the flux composition above and below the wire. That is, when the wires are arranged horizontally, variations occur in the circumferential direction, and when the wires are arranged vertically, variations occur in the vertical direction. Therefore, it is recommended to divide the materials with large differences in specific gravity into separate groups, change the orientation of each group in separate painting booths, and apply redundant coating. The flux used in the present invention contains a non-powdered adhesive as described below, but since this is melted during heating and baking and functions as a binder, it is not suitable for repeated coatings as described above. If so, their respective presence in each composition is required. Therefore, it is recommended that the powdered adhesive be mixed evenly with each of the raw material powders.

Powdered adhesives include low melting point glass adhesives, inorganic polymer adhesives, organic polymer adhesives, etc., but phenolic resin, which is a carbon bond adhesive, has a high adhesive strength and baking conditions. It was perfect in terms of

Flux often contains non-conductive substances such as carbonates, silicates, and fluorides, as well as conductive substances such as ferroalloys, but conductive substances do not adhere electrostatically, so these should not be mixed. It is necessary to coat the surface with an insulating material in the previous preliminary treatment.
In this case, if an adhesive for fixing the flux is used as the insulating material for surface coating, the effect of killing two birds with one stone can be obtained.

The electrostatic coating booth 4 shown in FIG. 1 employs the electrostatic dipping method, and a porous ceramic plate 9 is arranged below the coating booth 8, on which electrodes are placed at approximately regular intervals. Electrodes 10 are arranged on the ceiling surface of the booth 8 as well as on the ceiling surface of the booth 8. These electrodes 10 are connected to a high voltage generator (not shown) and receive a negative applied voltage. On the other hand 11
is a ground wire that is in contact with the wire W _-1 running inside the booth, and strong electrolysis occurs between the electrode 10 and the ground wire 11. Therefore, when air is blown from the air blowing fan 12 and the flux component placed on the ceramic plate 9 is blown up to form a fluidized bed, the powder becomes negatively charged in the ionized air and becomes grounded. It adheres to the outer periphery of wire W _-1 . If it is desired to increase the amount of Flux F deposited, it is sufficient to perform repeated coatings. In this case, it is preferable to increase the charging voltage sequentially, for example -60 KV at the beginning and -130 KV at the final stage.

FIG. 2 is an explanatory diagram showing an example of coating by electrostatic spraying, in which the wire W _-1 is being electrostatically sprayed in the coating booth 8 while traveling in the direction penetrating the page.
Flux F is stored in the hopper 13 and is blown into the booth 8 via the spray gun 15 by the constant supply injector 14. 1
Reference numeral 6 is a high voltage generator, 10 is an electrode, and 11 is a ground wire, which charges the flux F that is sprayed toward the wire W -1.In this state, the flux F that is sprayed toward the wire W _-1 will be charged to the spray gun 15 side of the wire W _-1 . Since the coating will be applied intensively, it is recommended to twist the wire W _-1 or arrange multiple spray guns around the wire W _-1 to spray uniformly around the periphery. Ru. Reference numeral 17 indicates a flow path for returning flux.

After electrostatic coating has been carried out in this manner, the wire may be sent to a heating and baking device to fix the flux F as described above, then inserted into a tubular wire, and then wire-drawn to a predetermined size. As described above, since the present invention adopts a method in which the flux is once attached to the wire and then inserted into the tubular wire, the filling rate of the flux may be uneven in the longitudinal direction or there may be local unfilled areas. There is no fear that this could happen,
A flux-cored wire of extremely stable quality can be obtained. However, electrostatic coating is used to apply the flux, and no liquid binder such as water glass is used at all, and since the flux is filled into the tubular wire immediately after heating and baking, the flux can be applied in an absolutely dry state. This, together with the fact that there are no seams in the steel shell, provides extremely high performance.

Next, examples of the present invention will be shown.

Example 1 A flux-cored wire was manufactured according to the method shown in FIG. 1 under the following conditions. After being filled with flux and drawn to a specified size (1.2 mmφ), the wire was subsequently degreased, washed, and copper-plated to improve electrical conductivity before being made into a product.

[Materials used and operating conditions]

Wire (W _-1 ): Low carbon steel, 1.0mmφ Tubular wire (W _-3 ): Low carbon steel, inner diameter 6.0mmφ outer diameter
10.0mmφ Flux: Basic flux (iron powder, Fe-
Mn, Fe-Si, Fe-Ti, _CaF2 , _TiO2 , _SiO2 ,
ZrO ₂ : However, these are mixed by insulating the surface with phenolic resin in advance) Powder adhesive: Phenol resin Electrostatic coating Conditions: Voltage 60KV Wire running speed 1m/
Firing conditions: 200°C x 30 minutes Flux coating thickness: 3 mm The obtained flux-cored wire has no seams on the outer skin, lubricants, etc. are completely removed, and is copper-plated, making it easy to feed. It was confirmed that both the flux and the conductivity were extremely good, and since the flux packing density was uniform and the degree of dryness was high, it exhibited extremely good weldability.

[Brief explanation of the drawing]

FIG. 1 is a schematic process explanatory diagram showing an embodiment of the present invention, and FIG. 2 is an explanatory diagram illustrating an electrostatic spray coating method. 1...Spool, 2...Rust removal/degreasing device, 3...
... Drying device, 4 ... Electrostatic coating equipment, 5 ... Heating and baking device, 6 ... Piano wire, 7a, 7b ... Telescopic die, W _-1 ... Wire, W _-2 ... Flux coating wire, W _-3 ...Tubular wire, W _-4 ...Flux-filled wire.

Claims (1)

[Claims] 1. A metal wire is run in the longitudinal direction in a coating booth, and a powder flux composition containing a powder adhesive is electrostatically applied to the outer surface of the wire, and then the flux is heated and baked. A method for manufacturing a flux-cored wire for welding, which comprises the step of inserting the wire into a steel pipe and drawing the wire. 2. In claim 1, manufacturing a flux-cored wire using a powdery flux composition in which the surface of the conductive material contained in the powdery flux composition is insulated and the entire surface is made of an insulating material. Method.