JP4208665B2 - Manufacturing method of recycled backing flux for single-sided submerged arc welding - Google Patents

Description

  The present invention relates to a method for producing a backing flux for single-sided submerged arc welding arranged on the back side of a welded portion of a material to be welded in single-sided submerged arc welding, and in particular, is obtained by regenerating a used backing flux. The present invention relates to a regeneration method of a regenerative backing flux for single-sided submerged arc welding.

  Conventionally, single-sided submerged arc welding has been performed in which a powdery flux is supplied to the part to be welded, the tip of the welding wire is thrust into this flux, and welding is automatically performed while the weld and arc are cut off from the atmosphere. It has been broken. Single-sided submerged arc welding is highly efficient and can be applied to welding of various structures including ships, because it can weld relatively thick plates by welding only on one side. When performing single-sided submerged arc welding, a backing flux for single-sided submerged arc welding may be disposed between the material to be welded and the backing copper plate (see, for example, Patent Documents 1 to 3).

  The backing flux for single-sided submerged arc welding is preferably a powder so that it can be in close contact with the welded part of the material to be welded before welding, and is preferably solid so that the bead part can be supported during welding. . Therefore, a single-sided submerged arc that is coated with a thermosetting resin on the surface of each powder in a powdery flux, is a powder before welding, and is solidified by hardening or burning off the thermosetting resin during welding. A backing flux for welding has been developed (see, for example, Patent Document 4).

Japanese Patent Laid-Open No. 5-337651 Japanese Unexamined Patent Publication No. 7-303989 Japanese Patent Laid-Open No. 10-314983 JP-A-11-90680

  However, the conventional techniques described above have the following problems. The single-sided submerged arc welding backing flux (hereinafter also simply referred to as flux) coated with the above-mentioned thermosetting resin is heated unevenly during welding. For this reason, in the flux after welding, the thermosetting resin was burned away by welding heat, and the flux was melted and solidified to become slag, and the thermosetting resin was hardened by welding heat and became a lump. The part and the part where the heat is not transmitted so much and the powder remains are mixed. Therefore, at least the powder portion of the used flux can be reused.

  However, when the used flux is recovered, it is recovered in a state where the above-mentioned powder part, lump part and slag part are mixed. And it is extremely difficult to separate only the powder portion from the used flux, and the work is not troublesome. For this reason, conventionally, the spent flux, including the powder part, has been disposed of as industrial waste. As a result, disposal costs are incurred and a new backing flux is used every time welding is performed, resulting in high welding costs.

  The present invention has been made in view of such problems, and provides a method for producing a regenerated backing flux for single-sided submerged arc welding that regenerates and produces a used one-sided submerged arc welding backing flux. Objective.

The method for producing a regenerative backing flux for single-sided submerged arc welding according to the present invention is used for welding in the method for producing a regenerative backing flux for single-sided submerged arc welding in which each powder surface is coated with a thermosetting resin. A heating step of removing the thermosetting resin by heating a backing flux not containing metal and alloy components to a temperature of 400 to 800 ° C. for 5 minutes or more, and separation for separating powder from the heated flux by sieving And a coating step of newly coating the powder with a thermosetting resin.

  In the present invention, by removing the thermosetting resin from the backing flux that has been used for welding, it is possible to pulverize the part of the used flux that has become agglomerated. Thereby, this powder can be easily separated from the slag portion of the used flux, and by recoating the separated powder with a thermosetting resin, the reproduction backing flux for single-sided submerged arc welding is regenerated, Can be reused.

The manufacturing method of the regenerative backing flux for other single-sided submerged arc welding according to the present invention is used for welding in the manufacturing method of the regenerative backing flux for single-sided submerged arc welding in which each powder surface is coated with a thermosetting resin. And a heating step of removing the thermosetting resin by heating the backing flux containing a metal or alloy component to a temperature of 400 to 600 ° C. for 5 minutes or more , and separating the powder from the heated flux by sieving And a coating step of newly coating the powder with a thermosetting resin.

  Thus, according to the present invention, by heating the single-sided submerged arc welding backing flux used for welding under a predetermined condition, the thermosetting resin is removed from the used flux to form a lump. The part can be pulverized. As a result, this powder can be easily separated from the slag portion of the used flux, and the surface powder of the separated powder is coated with a thermosetting resin again, thereby providing a backing flux for single-sided submerged arc welding. Can be played and reused. As a result, the welding cost for submerged arc welding can be reduced.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. The regenerated backing flux for single-sided submerged arc welding according to this embodiment is produced by regenerating a used backing flux for welding. This flux is in the form of powder, and the surface of each powder is coated with a thermosetting resin. The ratio of the thermosetting resin to 100% by mass of the flux is, for example, 1.0 to 8.0% by mass. An example of the composition of the flux excluding the thermosetting resin is shown in Table 1. The particle size in the range of 212 μm to 1.7 mm accounts for 70% by mass or more of the whole. Examples of the thermosetting resin include a phenol resin, a furan resin, and a xylene resin.

  Next, a manufacturing method of the regenerative backing flux for single-sided submerged arc welding according to the present embodiment configured as described above, that is, a method of regenerating used flux will be described. First, after performing single-sided submerged arc welding, the backing flux after welding is collected. Table 2 shows the state of the flux after welding.

  As shown in Table 2, in the flux recovered after welding, that is, used flux, (1) the portion (powder portion) where the heat is not transmitted so much and remains as powder (2) due to the welding heat A portion (lumped portion) where the thermosetting resin is cured and formed into a lump (3) and a portion (slag portion) where (3) the thermosetting resin is burned out by welding heat and the flux is melted and solidified to become slag. It is mixed. Note that (3) (slag portion) may be attached to (2) (lumped portion).

  Of the flux after welding, (1) (powder portion) shown in Table 1 can be used again as it is. In addition, (2) (lumped portion) can be reused by removing the remaining thermosetting resin to form a powder and then coating the thermosetting resin again. On the other hand, (3) (slag portion) cannot be reused and must be discarded. As described above, when the used flux is collected, it is collected in a state where the above (1), (2), and (3) are mixed. For this reason, in order to reuse the used flux, it is necessary to separate at least (3) (slag portion) from (1) (powder portion) and (2) (lumped portion).

  However, when the used flux mixed with the above (1), (2), and (3) is separated by, for example, a sieve, it can be reused together with (3) (slag portion) (2) ( The lump part) is removed together. Further, if (2) (lumped portion) is crushed before separation, (3) (slag portion) is also crushed, and again only (3) (slag portion) cannot be separated. Furthermore, in order to pulverize the (2) (bulk portion), a method of using a solution to remove the remaining thermosetting resin by a chemical reaction may be considered, but it is extremely difficult to treat the solution after the treatment. There is a problem.

  As a result of conducting various studies on these problems, the present inventors conducted heat treatment on the recovered flux after welding under predetermined conditions, and the thermosetting resin adhering to the flux was removed, and (2 ) (Lumped part) was pulverized and found to return to the same appearance color as the new flux. At this time, only the coating layer of the thermosetting resin is removed while (1) (powder portion) remains in powder form, and (3) (slag portion) remains unchanged. Therefore, after heat-treating the used flux (2) (the lump part) is pulverized, this flux is passed through a sieve, for example, to separate (3) (slag part) from the used flux can do.

  The reproduction | regenerating method of the reproduction | regeneration backing flux for single-sided submerged arc welding which concerns on this embodiment is demonstrated in the order of the process. First, the used flux after welding is collected. In this used flux, (1) (powder portion), (2) (lumped portion), and (3) (slag portion) shown in Table 2 are mixed.

  Next, the used flux is subjected to heat treatment. At this time, when the iron powder or alloy component is not contained in the flux, the heat treatment temperature is 400 to 800 ° C., and when the iron powder or alloy component is contained in the flux, the heat treatment temperature is 400 to 600. ℃. The heat treatment time is 5 minutes or longer. Thereby, the coating layer which consists of a thermosetting resin is removed from (1) (powder part) and (2) (lumped part). As a result, (2) (the block portion) is pulverized because the thermosetting resin layer that has combined the fluxes is removed. In addition, (1) (powder part) remains as powder, and (3) (slag part) originally has almost no thermosetting resin layer left, and the flux itself is melted and solidified. It does not change even with the aforementioned heat treatment.

  Next, the heated flux is sieved to remove (3) (slag portion). The mesh size of the sieve is, for example, a nominal dimension of 0.85 to 2.36 mm, for example, 10 mesh (nominal dimension: 1.70 mm).

  Next, (3) (slag portion) is removed, and the surface of each powder of the flux which is only powder is newly coated with a thermosetting resin to form a coating layer. The method for coating the thermosetting resin is not particularly limited and may be a conventional method. For example, a powdered or solid thermosetting resin material is heated and mixed with a flux to coat the surface of each powder of the flux with the thermosetting resin. Alternatively, a thermosetting resin is dissolved in a solvent such as ethanol, and this is added to a powdery flux and mixed. Then, the surface of each powder of the flux is coated with a thermosetting resin by drying at a temperature at which the resin does not melt. Thereby, the reproduction | regeneration backing flux for single-sided submerged arc welding which concerns on this embodiment mentioned above is reproduced | regenerated.

  Depending on the welding conditions and the like, a lump part may not be formed in the used flux. In such a case, it is not always necessary to perform the above-described heat treatment and thermosetting resin coating treatment, and using a sieve having a maximum particle size of the nominal particle size of the flux, the powder portion and the slag portion are separated. They can be separated from each other.

  Hereinafter, the reason for the numerical limitation in each constituent requirement of the present invention will be described.

Heat treatment temperature: 400 to 800 ° C
The thermosetting resin adhering to the used flux has the property of starting to generate heat and being burned off when heated to a temperature of 400 ° C. It is difficult to remove the thermosetting resin at a heating temperature of less than 400 ° C. It is. On the other hand, the upper limit of the heat treatment temperature varies depending on the flux composition. When the flux does not contain iron powder, deoxidizer, and alloy components, that is, when the flux cannot contain these components, and when these components can be contained but are not actively contained, the heat treatment temperature The upper limit is 800 ° C. When the heat treatment temperature exceeds 800 ° C., the flux is melted during the heat treatment, and the cooled flux is crystallized, so that it contains a large amount of water as crystallization water. That is, the hygroscopicity of the flux is increased. When such a flux is regenerated and used for welding, pits and blow holes are likely to occur. Further, in the case of a flux that does not contain iron powder, a deoxidizer, and an alloy component, when the heat treatment temperature exceeds 800 ° C., fluoride contained in the flux is decomposed. When such a flux is regenerated and used for welding, the meltability of the flux becomes poor and the back bead shape becomes unstable. Therefore, the heat treatment temperature needs to be 400 to 800 ° C.

  Moreover, deoxidation components, such as a Fe-Mn type alloy and a Fe-Si type alloy, may be added to a flux. Further, iron powder or alloy components may be added to the flux. In such a case, if the heat treatment temperature exceeds 600 ° C., the alloy components and iron powder may be oxidized, so the heating temperature needs to be 600 ° C. or less. That is, when the heat treatment temperature exceeds 600 ° C. and the deoxidizer is oxidized, the deoxidation effect is lowered and the function as the deoxidizer is not achieved. As a result, the amount of oxygen in the weld metal increases, the amount of slag increases, and the back bead shape becomes unstable. Further, when the iron powder is oxidized, the amount of oxygen in the weld metal cannot be controlled, and the amount of slag increases and the back bead shape becomes unstable. Furthermore, when the alloy component is oxidized, the weld metal portion after welding does not have the designed alloy composition. In addition, the amount of gas generated during welding increases and gas defects occur.

  Further, the flux may be manufactured as a sintered flux containing a metal carbonate or the like. Metal carbonate decomposes by arc heat during welding to generate carbon dioxide gas and shields molten metal. However, when the heat treatment temperature exceeds 600 ° C, the metal carbonate decomposes during heat treatment. Therefore, this effect cannot be obtained during welding. Therefore, when the deoxidizer, iron powder, alloy component, and metal carbonate are contained in the flux, the heat treatment temperature is preferably 600 ° C. or lower.

Heat treatment time: 5 minutes or more The heat treatment time varies depending on the amount of used flux and the heat treatment temperature, but if the heat treatment time is less than 5 minutes, the remaining thermosetting resin is surely removed from the used flux. It is difficult to remove. Therefore, the heat treatment time needs to be 5 minutes or longer.

  FIG. 1 is a graph showing the effect of heat treatment conditions on powdering of a lump portion of used flux, with the heat treatment time on the horizontal axis and the heat treatment temperature on the vertical axis. The white circle (◯) shown in FIG. 1 indicates that the thermosetting resin has been completely removed and the lump portion has been powdered, and the black circle (●) indicates that the thermosetting resin remains and the lump portion has been completely powdered. Indicates that it was not converted. As shown in FIG. 1, in order to completely remove the thermosetting resin from the used flux and to completely pulverize the lump portion, it is preferable to hold at a heat treatment temperature of 400 ° C. or more for 5 minutes or more. .

As a method of separating the powder portion and slug portions after heat treatment, Ru simplest der how to use the aforementioned sieve.

  Hereinafter, the effect of the embodiment of the present invention will be specifically described in comparison with a comparative example that deviates from the scope of the claims. First, three types of backing flux for single-sided submerged arc welding shown in Table 3 were prepared. Table 4 shows the composition and particle size of these fluxes. In addition, the raw material mixed flux shown in Table 3 is a mixture of raw materials (ore powder). Next, single-sided submerged arc welding was performed using these three types of fluxes. The conditions for this single-sided submerged arc welding are shown in Table 5.

  After welding, the used backing flux was collected and subjected to heat treatment under various heating conditions. Table 6 shows the heat treatment temperature and the heat treatment time at this time. And the powdered state after heat processing and the presence or absence of the thermosetting resin were evaluated. The evaluation results are shown in Table 6. In Table 6, the case where the lump part was completely powdered was designated as “◎ (very good)”, and a part of the lump remained, but the case where this lump was easily pulverized was designated as “◯ (good)”. ”, A case where some lump remained and this lump was not easily pulverized was designated as“ Δ (normal) ”, and a case where the lump was not pulverized at all was designated as“ x (defective) ”. The presence or absence of the thermosetting resin was confirmed by the presence or absence of an exothermic reaction due to differential heat, the mass change before and after the heat treatment of the flux, and the analysis by a gas chromatography mass spectrometer.

  Next, among the fluxes after the heat treatment, only the ones in which the lump portion was pulverized and the thermosetting resin did not remain, the powder portion and slag were separated by a sieve. At this time, the mesh size of the sieve was 10 mesh (nominal dimension: 1.70 mm). Next, a thermosetting resin was newly coated on each powder surface of the flux powdered in this way to form a coating layer, and a single-sided submerged arc welding backing flux was regenerated. The coating was performed by heating and mixing the above-mentioned thermosetting resin material with a flux. Then, single-sided submerged arc welding was performed using this regenerated flux as a backing flux, and the back bead shape of the welded portion was evaluated. This single-sided submerged arc welding was also performed under the conditions shown in Table 5.

  Of the Examples and Comparative Examples of the present invention shown in Table 6, Example No. In Nos. 1 to 6, the heat treatment temperature is Flux No. containing an alloy component. Example No. using A For Nos. 1 and 6, Flux No. 400 to 600 ° C. containing no alloy components. Example No. using B and C For 2 to 5, the temperature was 400 to 800 ° C., and the heat treatment time was 5 minutes or more, so that the lump part of the used flux was all pulverized, and there was no residual thermosetting resin. I was able to play it. For this reason, as a result of welding using this regenerated flux, a good back bead shape was obtained.

  On the other hand, Comparative Example Nos. In Nos. 7 to 9, since the heat treatment temperature was low at less than 400 ° C., the bulk portion was not pulverized and the flux could not be regenerated for any type of backing flux. Comparative Example No. No. 10, Flux No. containing alloy components. Although A (bonded flux) is used, since the heat treatment was performed at a temperature exceeding 600 ° C., the flux could be regenerated, but the alloy components in the flux were oxidized. As a result, when this flux was regenerated and welded as a backing flux, the oxygen content in the molten metal could not be controlled, the amount of gas generated during welding increased, and a gas defect occurred in the back bead. . Further, Comparative Example No. In No. 11, since the heating time was as short as 2 minutes, heat was not transmitted to the entire flux, and the lump was not pulverized.

It is a graph which shows the influence which heat processing conditions have on the pulverization of the lump part of a used flux, taking heat processing time on a horizontal axis and taking heat processing temperature on a vertical axis | shaft.

Claims (3)

In the manufacturing method of the regenerative backing flux for single-sided submerged arc welding in which each powder surface is coated with a thermosetting resin, the backing flux that has been used for welding and does not contain metal and alloy components is brought to a temperature of 400 to 800 ° C. A heating step for removing the thermosetting resin by heating for 5 minutes or more, a separation step for separating the powder from the heated flux by sieving, and a coating step for newly coating the powder with the thermosetting resin And a method for producing a regenerative backing flux for single-sided submerged arc welding. In the method for producing a regenerative backing flux for single-sided submerged arc welding in which each powder surface is coated with a thermosetting resin, the backing flux that has been used for welding and contains a metal or alloy component is brought to a temperature of 400 to 600 ° C. A heating step for removing the thermosetting resin by heating for 5 minutes or more, a separation step for separating the powder from the heated flux by sieving, and a coating step for newly coating the powder with the thermosetting resin And a method for producing a regenerative backing flux for single-sided submerged arc welding. 3. The separation step according to claim 1, wherein the separation step is a step of separating the one-sided submerged arc welding backing flux after heating through a sieve having a nominal size of 0.85 to 2.36 mm. Manufacturing method of regenerative backing flux for single-sided submerged arc welding.

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