JPS58181496A - Production of flux cored wire for welding - Google Patents

Abstract

PURPOSE:To obtain a titled wire which causes less segregation of a flux and has no seam with a simple production stage by reducing a large-diameter steel pipe, which is packed therein with the flux, by hot rolling then subjecting the same to the area reducing processing by cold drawing and surface treatment. CONSTITUTION:A flux 2 having controlled components is packed into a steel pipe 1 of D>=50mm., 0.1<=t/D<=0.3 in the diameter D and wall thickness (t) thereof. Both ends of the pipe 1 are drawn with a swaging machine or the like to provide gas vent holes 5 thereby forming gas vent parts 3. The parts 3 play the role of preventing the outflow of the flux 2 and discharging thermally expanded air, steam, etc. during rolling. Gas vent seals 4 discharge gas efficiently to minimize the leakage of the flux. Such steel pipe as a departing material is heated in a soaking pit and is then hot rolled to reduce the diameter of the pipe 1 considerably, whereby the flux-packed steel pipe is obtained. The gas vent parts thereof are removed, whereafter the pipe is subjected to cold drawing and a surface treatment such as plating or the like, whereby the flux cored wire for welding having a prescribed wire diameter is obtained.

Description

[Detailed description of the invention] This invention relates to a method for producing earrings.

Flux-cored wire for welding uses a deoxidizer. It is a wire with a composite structure in which a metal-sheathed steel pipe is filled with granular flux consisting of a slag-forming agent, etc., and is used for a wide range of applications, from welding mild steel to low-alloy and high-temperature alloy steel.

Conventional methods for producing flux-cored wire for welding can be roughly divided into two methods. One method is to form a thin steel strip into a U-shape and then weld it in the form of powder particles after predetermined composition adjustment. There is a method of uniformly filling the wire with flux, forming it into a predetermined cross-sectional shape, and then wire-drawing it. Although this method is a manufacturing method commonly used at present, the flux-cored wire manufactured by this method has various drawbacks because it has seams. In other words, the seams are likely to open, and moisture on the outer surface of the wire or organic substances such as lubricants used during the manufacturing process enter the flux inside the sheathed steel pipe through the openings. When welding using such a wire, it may increase the diffusible hydrogen in the weld metal or promote the oxidation of the inner skin wall of the wire, increasing the oxygen in the weld metal, resulting in mechanical damage to the weld. This will lead to performance deterioration.

Also, since it has seams, it cannot be plated and therefore has poor rust resistance.

Other methods overcome the shortcomings of the above methods and include welding the joints of the steel strips after filling with flux, or
Another method is to fill the steel pipe with flux. The method of welding the joints of copper strips has the drawback of poor productivity and increased cost.

Also, among the methods of filling flux into steel pipes, one straight pipe is used.
This filling method has a limit on the amount of filling units, and companies
It is difficult to produce locally. That is, if the length of the steel pipe exceeds lom, it becomes very difficult to transport the steel pipe and the flux filling device becomes complicated. As a method for solving this problem, for example, a technique described in Japanese Patent Publication No. 45-30937 is known. In this method, a long steel pipe is coiled and flux is transported and filled into the pipe through the open part of the pipe using vibration. Although this method does make the filling unit larger, it takes a long time to fill the flux into the long and thin steel pipe, and because each flux has a difference in specific gravity and particle size, back mixing occurs during vibration filling. This causes segregation in the filled flux, making it difficult to satisfy the product quality of the flux-cored wire. To solve this problem, it is possible to prepare the flux in advance and then granulate it with a binder such as water glass. However, this makes it easier for the flux to absorb moisture, so after filling it, the flux is heated at around 500C in a heating furnace.
It is necessary to incorporate a water removal step that involves heating for more than 1 hour. Segregation of flux can be eliminated to some extent by granulation, but it is not satisfactory.

The first object of the present invention is to provide a welding flux-cored wire with less flux segregation and no joints, the second object is to simplify flux filling, and the third object is to provide a welding flux-cored wire with less flux segregation. The object of the present invention is to provide a flux-cored wire with small seams, less segregation of flux, less moisture and gas content, and low cost.

In order to achieve the above object, in the present invention, the pipe diameter and the pipe wall thickness t are such that D ≧50 y and 0.1≦t/D≦0.
．． 3 steel pipes are filled with flux, the steel pipes are hot-rolled and stretched, and then cold-drawn to form wires of a predetermined wire diameter.
This is then surface treated. That is, in the present invention, the starting material is a large-diameter steel pipe filled with flux whose composition has been adjusted in advance, and this is hot-rolled to significantly reduce its cross section, and then cold-drawn and surface-treated. By performing this treatment, we can completely remove moisture in the flux, prevent the segregation of the filling flux in the wire, and perform surface treatments such as plating to improve the quality of the flux-cored wire for product welding, as well as shorten manufacturing time. Achieve lower costs by simplifying the manufacturing process.

The reason why the diameter of the steel pipe is limited to 0850 m in the present invention is that if D<50 m, the filling unit becomes too small, which is disadvantageous in terms of simplifying work, increasing efficiency, and equalizing product quality. be. Although the upper limit of the diameter of the steel pipe is not particularly limited, it is approximately 200 U from the viewpoint of hot rolling equipment capacity.

Also, the ratio t/D of the steel pipe thickness and the pipe wall thickness t is 0, 1 <, t
The reason for specifying /D≦0.3 is that if t/D is less than 0.1, the strength will be insufficient in the subsequent cold wire drawing, and wire breakage will easily occur during wire drawing, which will impede productivity. Also, in the final process, when the wire is wound onto a spool as a product, breakage occurs due to insufficient strength. On the other hand, if t/D exceeds 0.3, flux filling rate (flux weight/wire weight)
This is because the deoxidizing agent, slag forming agent, etc. in the flux necessary for welding flux-cored wire are insufficient.

The diameter of the flux-filled steel pipe after hot rolling, that is, the finished diameter of hot rolling, is not particularly limited, but it is 5 to 20 mm in consideration of the current general-purpose hot rolling equipment and the cold wire drawing process in the subsequent process.
A value within the range of u is appropriate.

Note that flux-filled steel pipes are subjected to hot rolling and exposed to high temperatures, but it is necessary to take into account the composition of the flux filled in the steel pipes so that the quality does not change due to this high-temperature heating. However, there are cases where it is necessary to fill in a welding flux with a low melting point, so the hot rolling temperature is slightly lower than the hot rolling temperature from a normal steel ingot, taking into consideration the deterioration of the flux. It is desirable that the temperature be the same. For example, the hot rolling temperature is set to 750 to 850°C.

In a preferred embodiment of the present invention, a gas venting portion is formed at one or both ends of the flux-filled steel pipe. It is formed in order to efficiently discharge gas that expands inside the pipe due to thermal expansion of the residual air inside the pipe, vaporization of water adhering to the flux, etc. to the outside of the steel pipe without causing the flux to flow out. Furthermore, during hot rolling, the filling flux as well as the gas leaks from the gas venting part, which may damage the rolling rolls, etc.
It is preferable to provide a tab section in the gas vent section to prevent leakage flux from dissipating.

Hereinafter, the present invention will be specifically explained with reference to the drawings.

Fig. 1 is a diagram showing a specific example of a flux-filled steel pipe that is a starting material for hot rolling. A gas venting hole 5 is provided to form a gas venting portion 3 by machining with a machine or the like. This gas venting part plays the role L1 of preventing flux from flowing out during rolling and also exhausting thermally expanded gases such as air and water vapor from the gas venting hole. Reference numeral 4 denotes a gas vent seal, which is provided in the gas vent hole 5 for the purpose of efficiently discharging gas and minimizing leakage of flux. The material for the gas venting seal 4 is preferably a thin steel plate with many gas venting holes, steel wool, glass wool, or the like.

Figure 2 shows that both ends of the flux-filled steel pipe shown in Figure 1 are
It is a figure which showed the example which provided the tab 7 for leakage flux dissipation prevention. The material of the tab is preferably the same as that of the steel pipe 1, and the shape is either cylindrical with the same diameter as the steel pipe 1 as shown in the figure, or a truncated conical shape with the diameter becoming smaller towards the end, so that the tab can be easily attached to the rolling roll. A shape that is easy to bite into is desirable.

By providing this tab 7, even if flux leaks from the gas vent hole 5, the flux remains inside the tab and does not dissipate. Note that if there is no leakage of flux from the gas vent hole 5 or the leakage amount is extremely small and does not cause any problem, it is not necessary to provide a tab. 6 is a welding part that connects the tab part and the steel pipe.

FIG. 3 is a sectional view showing another example of a flux-filled steel pipe, and FIG. 3b is a sectional view taken along the line IB-IB in FIG. 3a. In this example, the gas vent portion 3' is formed by welding a stopper 8 having a plurality of (four in the illustrated example) gas vent holes 5' to the steel pipe 1.

The material of the stopper 8 is preferably the same as that of the steel pipe 1. 4' is a gas venting seal, and 7' is a tab for preventing dissipation of leaked flux, which has a truncated conical shape with a smaller diameter toward the end.

The present invention uses the flux-filled steel pipe configured as described above as a starting material, heats it in advance in a soaking furnace, significantly reduces the steel pipe diameter in a hot rolling process, and fills it with flux to a diameter of 5 to 2011 J. Use steel pipe. Next, the gas vent portions at both ends of the flux-filled steel pipe are cut off, and then surface treatments such as cold wire drawing and plating are performed to obtain a welding flux-cored wire of a predetermined wire diameter.

The relationship t/D between the diameter of the steel pipe and the pipe wall thickness t is determined by the density of the flux to be filled and the flux filling rate of the target wire. Before filling, the flux is thoroughly mixed with a mixer to prevent segregation, and then the flux is filled. The amount of filling is adjusted by adjusting the packing density of the flux.

In the present invention, since the flux-filled steel pipe is exposed to high temperatures during the hot rolling process, moisture in the flux is inevitably discharged to the outside. The manufacturing process can be simplified without requiring a water removal process.

EXAMPLE A flux-cored wire for carbon dioxide gas welding was manufactured using the flux-filled steel pipe shown in FIG. 1 as a starting material and according to the manufacturing method of the present invention described above. Table 1 shows the manufacturing conditions.

Table 1 It was confirmed that in the wire thus produced, the moisture in the filling flux was almost completely removed, and there was no segregation of the flux. Also, since the wire surface is copper plated, it has good rust resistance.

When welding was performed using this wire, both the wire feedability and welding workability were good, the amount of diffusible hydrogen and oxygen in the weld metal was low, and the mechanical properties were extremely good.

As described above, according to the present invention, it is possible to obtain a flux-cored wire for welding with good quality, and it is also possible to shorten the manufacturing time and simplify the manufacturing process, and the industrial value of the present invention is Extremely large.

[Brief explanation of the drawing]

FIGS. 1, 2, and 3a are longitudinal sectional views of a flux-filled steel pipe used for carrying out the present invention, and FIG. 3b is a sectional view taken along line IB-IB in FIG. 3a. 1: Steel pipe 2: Flux 313': Gas vent section 4, 4/: Seal 5 g 5': Gas vent hole 6: Welded section 7, 7/: Tab 8:
Patent applicant: Nippon Steel Welding Industry Co., Ltd.

Claims (7)

[Claims] (1) Pipe diameter and pipe wall thickness t are D≧50 and 0.1≦
A flux-cored wire for welding is produced by filling a steel pipe with t/D≦0.3 with flux, hot rolling the steel pipe to elongate it, then cold drawing it into a wire of a predetermined wire diameter, and surface-treating the wire. Production method. (2) A method for manufacturing a flux-cored welding wire according to claim 1, wherein at least one end of a steel pipe filled with flux is squeezed and then the steel pipe is hot-rolled. (3) A method for manufacturing a flux-cored wire for welding according to claim (2), which comprises hot rolling a steel pipe with a gas vent hole formed at the narrowed end. (4) A method for manufacturing a wire to be inserted into a welding flank according to claim (3), wherein a tab is fixed to the narrowed end and then hot rolled. (5) Manufacture of a flux-cored wire for welding according to claim (1), in which an end plate is fixed to at least one end of a steel pipe filled with flux, and then the steel pipe is hot-rolled. Method. (6) The method for manufacturing a flux-cored wire for welding according to claim (5), wherein the end plate has a gas vent hole. (7) The method for manufacturing a flux-cored wire for welding according to claim 1, wherein the steel pipe is hot-rolled after a tab is fixed to the end plate.