JPS5854918B2 - Manufacturing method and device for molten flux for welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for producing a melt-type flux for general welding, such as a low-hydrogen melt-type flux with excellent crack resistance used in submerged arc welding of high-grade steel.

With the advancement of industrial technology in recent years, it has also been used as an automatic welding material.
Applicability to high tensile strength steel of 80 kg/m4 class or higher is now required.

A major problem associated with welding such high-grade steels is cold cracking caused by hydrogen.

It is known that the most effective measure against this problem is to reduce the amount of hydrogen absorbed by the weld metal, that is, to reduce the hydrogen source in the flux.

Conventionally, molten flux for submerged arc welding is melted in a suitable melting furnace, then brought into direct contact with cooling water to rapidly solidify into fine particles, and then undergoes a drying process. It has been produced by pouring it into a container or surface plate, allowing it to cool, and then going through a process of coarsely crushing the solidified plate.

The present inventors conducted a detailed study on the relationship between the above-mentioned conventional manufacturing method and the hydrogen absorption amount of each flux, and as a result, discovered the following new fact.

Firstly, the conventional method of contacting with water generally absorbs more hydrogen than the method of cooling on an iron plate, although it depends on the cooling rate.

This is because a considerable amount of basic components in the flux composition react with water upon contact with water, resulting in Ca(OH)2, Mg(OH)2,
) 2. This is considered to be due to the fact that Mn(OH)2 remains in the flux in the form of hydroxide.

It is recognized that these hydroxides do not release water molecules under normal drying conditions of about 300 to 400°C, but dissociate as hydrogen under the high-temperature arc during welding and enter the molten steel. It has become clear that the conventional production method using granulation is inappropriate for producing fluxes with low hydrogen uptake.

Second, even with the conventional manufacturing method of cooling on a fixed thick steel plate, there is still a hydrogen source that poses a problem when welding on an industrial scale.

This is thought to be due to the formation of crystals during the manufacturing process, and as a characteristic of crystals, alkaline earth crystals also have crystal water, so they have a high hygroscopic ability, and the hydration This is thought to result in the generation of hydrogen in the arc atmosphere during welding, similar to the production of hydrogen.

FIG. 1 shows the results of an experiment regarding the relationship between the passage of time and the amount of moisture absorbed for crystalline flux and amorphous flux, that is, glassy flux.

From this figure, it is clear that the glassy flux absorbs less water and does not increase after about 4 hours, whereas the crystalline flux absorbs more water and increases linearly with time. Ta.

Therefore, when a molten flux is cooled and solidified, whether or not it becomes a uniform amorphous glass without forming crystals depends on the solidification thickness specified by the flux composition and cooling. Depends on speed.

Therefore, if the entire surface of the flux on a thick iron plate can be cooled under uniform cooling conditions, it can be made glassy by reducing the thickness to within the limits determined by the composition of the flux.

For practical flux, this value is 10 to 30
If the thickness exceeds this limit,
It was found that heat of crystallization is generated and the heat possessed by the flux itself brings about a slow cooling effect, resulting in partial crystallization.

In addition, even if the thickness is within the above limit thickness, under conventional cooling conditions on fixed thick plates where heat flow is not uniform, local crystals may be present in the glass due to the recuperation effect, etc. It turned out to be true.

Quantifying and classifying such crystalline materials is difficult in practice, and the only way to determine whether or not they exist is to qualitatively determine their presence or absence. It is relatively easy to be exposed on the surface of the flux.

Crystalline materials have a larger volume than glassy (amorphous) materials, so when crystals form from glassy materials, the structure becomes distorted and is not smooth, exposing a large physical surface area or a chemically active interface. Therefore, it is thought that the hygroscopic ability functions.

By the way, in the conventional fixed plate type flux production method in which the flux is poured into a container with a fixed volume, it is difficult to satisfy the cooling conditions for uniformly cooling the entire surface of the flux, and therefore, there is always a considerable amount of crystalline material mixed in. In this sense, it has become clear that the conventional method using fixed thick iron plates is also inappropriate for producing vitreous flux.

As a result of research, the present inventors succeeded in devising an innovative method and apparatus that can be readily adapted to the industrial production of vitreous flux, which cannot be produced using conventional methods.

That is, the present invention provides a method for producing molten flux, in which molten flux is continuously flowed out of a melting furnace, and the flowed flux is rapidly cooled by contacting the other surface of a rotating metal tube whose one surface is forcedly cooled. 1. A method for producing a molten flux, which comprises solidifying it into a glassy thin film, and crushing the glassy thin film into powder.

A rotating metal tube whose outer surface is forcibly cooled, a gutter for flowing molten flux into the inner surface of the metal tube, a crushing device button for solidified flux inside the metal tube, and a flux delivery device below the crushing device are provided. A manufacturing device for molten flux for welding, which is characterized by:

A rotating metal tube whose inner surface is forcibly cooled and an auxiliary metal roll that rotates close to the outer surface of the metal tube with a narrow gap are provided. This is a welding molten flux manufacturing device characterized by having a flux discharge device provided at the bottom of the crushing device.

Here, when implementing the present invention, if the temperature of the molten flux before cooling is low, the fluidity of the flux is poor, so a solid phase is generated in the thickness direction of the flux at the moment it contacts the metal tube surface. Once growth begins, crystalline formation will occur due to the slow cooling effect in areas far from the metal surface, and the complete effect of the present invention cannot be expected. It is better to take a look.

As mentioned above, the essential feature of the present invention is to form a glassy thin film, thereby obtaining a flux with a small amount of absorbed hydrogen, but the thickness of this thin film is different from that of a conventional product cooled on a thick iron plate. Since it is thin compared to the thickness, it is extremely easy to crush it, which is a significant effect on manufacturing operations.

The method of the present invention will be explained below with reference to the drawings.

2 and 3 show an embodiment of the apparatus to which the method of the present invention can be applied. Flux 1, which is maintained at a temperature moderately higher than the liquidus temperature, flows into thin-walled metal tube 3 through gutter 2.

The metal tube 3 is rotated by a rotating mechanism 4 such as a rotary gear or a roller whose rotation speed can be arbitrarily adjusted, and its inclination angle is set to a desired inclination by a push-up device 5 using hydraulic pressure or the like.

In this example, the outer surface of the metal tube is forcibly cooled using the water spray 6, but this can also be done using a water jacket method.Also, in order to further strengthen the cooling of the molten flux, blowing air into the tube may be used. May be added.

The molten flux that has flowed into the lower part of the metal tube starts to solidify from the contact surface with the inner wall of the metal tube along the inner surface of the metal tube as the metal tube rotates, and rises while forming a thin film.

At this time, in order to obtain a uniform glassy solidified layer, it is necessary to adjust the flux thickness by selecting the tube cooling conditions, rotation speed, inclination angle, tube diameter, and tube length according to the composition. However, this condition can be easily set by experiment.

The glassy thin film 8 that has continuously risen along the inner wall of the tube as the metal tube rotates as described above is separated from the inner surface of the rotating tube by a guide 9 installed at a desired position in the upper part of the metal tube. The glass-like seven lacs 11 that are crushed by the crusher 10 continuously fall onto a conveyor 12 such as a belt conveyor and are conveyed out of the metal tube.

FIG. 4 shows another embodiment of the apparatus to which the method of the present invention can be applied, in which 3' is a rotating metal tube whose inner surface is forcedly cooled, and 13 is a rotating metal tube with a narrow gap between the outer surface and the outer surface of the rotating metal tube 3'. Auxiliary metal rolls rotate close to each other at a distance, 8' is a glass-like solidified flux layer, 9' is a guide, and 10' is a solidified flux crushing device provided at the outer lower part of the rotating metal tube.

Although not shown, a flux transport device is provided at the bottom of the crushing device.

The apparatus shown in FIG. 2 or 4 allows continuous operation.

Next, the production of flux and the performance of the flux by the method of the present invention using the apparatus shown in FIG. 2 or FIG. 4 will be explained with reference to Examples and Comparative Examples.

EXAMPLE In a heating furnace, fluxes of three compositions, acidic (a), neutral (a), and basic (c) were melted, and while maintaining the desired temperature, they were solidified and turned in steps 2 and 3, and cooled by the apparatus shown in FIG. 4. Processed.

Table 1 shows the processing conditions at this time.

All of the resulting fluxes were completely glassy.

Moreover, since it was in a thin film form, coarse crushing and subsequent crushing were easy.

※※ continuation,
A welding performance test was conducted using the flux obtained in this example.

Table 2 shows this result and the results for the comparative example flux.

Flux, A, B, C is a glass-like thin film produced by the method of the present invention, whereas flux, which has the same composition as the inventive example when melted, is a thick iron plate. These were manufactured by solidifying them to a thickness of about 20 mm by leaving them to cool at the top, and those manufactured by immersing them in water to rapidly cool them, crushing them, and drying them.

In each case, the flow was rectified and comparison welding was performed at the same time on the day after melt manufacturing.

As is clear from the above examples, the flux obtained by the method of the present invention maintains a significantly lower amount of hydrogen than the flux obtained by the conventional method.

By carrying out the method of the present invention, it is not only possible to produce the low-hydrogen flux, but also the apparatus of the present invention allows cooling of the molten flux under uniform conditions, and it is possible to form a thin film in a desired range. Therefore, the glass-like thin film flux can be manufactured reliably and easily.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing moisture absorption characteristics depending on flux properties. Figures 2 and 3 are route diagrams for explaining the device as an embodiment of the second invention, in which 1... molten flux, 2... gutter, 3... thin-walled metal pipe, 4... Pipe rotation mechanism, 5... Push-up device, 6.
...Water-cooled spray, 7...In-tube flow flux, 8...
Flux solidified layer, 9... guide, 10... coarse crusher, 11... coarsely crushed flux, 12... recovery machine. FIG. 4 is an explanatory diagram of another embodiment of the device of the present invention, in which 1'... molten flux, 3'... thin-walled metal tube, 1
3...Auxiliary metal roll, 8'...Flux solidified layer, 9'...Guiding guide, 10'...Crushing machine.

Claims (1)

[Claims] 1. A method for producing molten flux, in which molten flux is continuously flowed out of a melting furnace, and the flowed flux is transferred onto the other surface of a rotating metal tube whose one surface is forcedly cooled. 1. A method for producing a molten flux for welding, which comprises the steps of: contacting the flux to rapidly cool and solidify it into a glassy thin film; and crushing and pulverizing the glassy thin film. 2. A solidified metal tube whose outer surface is forcibly cooled, a gutter that flows molten flux into the inner surface of the metal tube, a crushing device for the solidified flux inside the metal tube, and a flux transport device below the crushing device. An apparatus for producing a molten flux for welding, characterized in that it is provided with: 3. A rotating metal tube whose inner surface is forcibly cooled and an auxiliary metal roll that rotates close to the outer surface of the metal tube with a narrow gap are provided, and a crushing device for solidified flux and the crusher are installed at the outer lower part of the rotating metal tube. 1. A welding flux manufacturing device, characterized in that a flux delivery device is provided at the bottom of the device.