JP2002331389A - Backing flux for one side welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a backing flux for one side welding capable of making practical use of resources by contriving the reclamation of a welding slug generated after submerged arc welding, excellent in hygroscopic resistance in the one side welding, and capable of forming easily a back bead having the uniform and appropriate excess weld height. SOLUTION: The welding slug generated by crushing the slug of a bond flux used for the submerged arc welding is used as a raw material powder, the welding slug is added in the content of 10 mass% or more against the total amount of other flux raw material and the welding slug, after carrying out granulation and baking using a bonding agent, a thermosetting resin is coated. This backing flux has 3.0 mm or less particle size, 1.20-1.80 g/cc bulk density, and the composition of the other flux raw material is SiO2 : 10-45 mass%, Al2 O3 : 2-25 mass%, MgO: 10-40 mass% and SiO2 +Al2 O3 : 25-50 mass%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention aims at recycling welding slag generated after submerged arc welding.
More specifically, the present invention relates to a backing flux for single-sided welding applied to welding of structures such as shipbuilding, and more particularly to a backing for single-sided welding which is excellent in moisture absorption resistance and can form a back bead having a uniform and appropriate extra height. Regarding flux.

[0002]

2. Description of the Related Art Due to the rapid increase in the amount of industrial waste in recent years and the social situation that it is not easy to construct a new industrial waste disposal site, there is a concern that there is a shortage of industrial waste disposal sites. Therefore, controlling industrial waste emissions has become a major issue today. Conventionally, the welding slag (hereinafter referred to as welding slag) in which the flux used for submerged arc welding melts during welding and then solidifies has been discarded as industrial waste. Considering utilization, recycling of welding slag is being studied. For example, Japanese Patent Application Laid-Open No. 51-21537,
1-188496 and JP-A-2000-10289
No. 2 discloses a technique in which a raw material whose components are adjusted in advance is added to welding slag to form a sintering flux.

Further, Japanese Patent Application Laid-Open No. 57-181796 discloses a method in which the mixing ratio of welding slag and unused flux is specified and the welding slag is recycled.

Further, Japanese Patent Application Laid-Open No. 63-188493 discloses a method in which a molten raw material whose components are adjusted in advance is added to welding slag to provide a flux of exactly the same quality as a new product.

However, these prior arts do not relate to a backing flux for single-sided welding, and do not disclose a technique which enables the application of welding slag used for submerged arc welding as a raw material of the backing flux. .

[0006] In the single-sided submerged arc welding method, a backing flux is disposed on a copper plate at a constant thickness, and the surface of the copper plate where the flux exists is used as a base material (steel plate).
And welding the copper plate from the side of the groove while pressing the copper plate against the side of the groove with the compressed air discharged from the air hose (see FIG. 4 described later). This welding method has the same effect as the double-sided welding, that is, a smooth back bead can be obtained without using a backing metal or the like. Penetration can be ensured, and the welding efficiency becomes extremely high. Therefore, the single-sided welding method is applied to welding of many structures mainly in the field of shipbuilding and the like.

In such a single-sided welding method, the molten metal on the back bead side is held by the copper plate, so that the tip of the back bead is cooled and solidified by the copper plate. However, in the single-sided welding method using this copper plate and flux, undercuts are easily generated in the back bead, and the cooling condition of the copper plate changes due to welding conditions, groove accuracy and welding distortion of the base material. Since the solidification of the back bead becomes uneven,
There is a disadvantage that the bead width and the extra height are difficult to be uniform.

[0008] Therefore, as a welding method in which these disadvantages are improved, Japanese Patent Application Laid-Open Nos.
The techniques disclosed in Japanese Patent Publication No. 126071 and Japanese Patent Application Laid-Open No. 58-84675 are known. JP-A-53-8574
No. 6, JP-A-58-84675 discloses a welding method in which two layers of powder of a backing flux are uniformly sprayed at an accurate height. In the welding method disclosed in JP-A-56-126071, two kinds of backing flux powders are uniformly mixed.

[0009]

However, in the welding method disclosed in JP-A-53-85746 and JP-A-58-84675, the powder of the backing flux having two layers is precisely formed. It is necessary to spray the material uniformly, but since this is an extremely difficult operation, there is a problem that the welding operation becomes complicated.

Also, in the welding method disclosed in Japanese Patent Application Laid-Open No. 56-126071, it is extremely difficult to uniformly mix two types of backing flux powder.
As a result, a back bead having a stable extra height may not be obtained.

Conventionally, in order to obtain a back bead having a stable extra height, the backing flux is in powder or powder form until the backing flux adheres to the back surface of the steel sheet, and is solid when forming the back bead. As such, a backing flux in which a thermosetting resin is coated on the particle surface of the flux is generally used. However, in this technology, since the thermosetting resin coating is applied, it cannot be re-dried before use.When left in the air for a long time, the backing flux absorbs moisture, and when used for welding, the backing flux is absorbed. Gas grooves or herringbone are generated in the bead. Therefore, the backing flux that has excessively absorbed moisture must be discarded, and the development of a backing flux having excellent moisture absorption resistance has been desired.

[0012] The present invention has been made in view of the above-mentioned problems, and resources can be effectively used by recycling welding slag generated after submerged arc welding. An object of the present invention is to provide a backing flux for single-sided welding, which is excellent and can easily form a back bead having a uniform and appropriate extra height.

[0013]

The backing flux for single-sided welding according to the present invention comprises a welding slag obtained by pulverizing a slag of a bond flux used for submerged arc welding.
It is characterized in that the raw material powder is added at a content of 10% by mass or more based on the total amount of the other flux raw materials and the welding slag.

The backing flux for single-sided welding, for example, is obtained by adding a binder to raw material powder obtained by mixing the powder of the welding slag and the powder of the other flux raw material, granulating the raw material powder, and then firing. Further, the sintered powder is coated with a thermosetting resin.

Another backing flux for single-sided welding is as follows:
For example, after the binder is added to the other flux material and granulated, before or after firing, the raw material powder of the welding slag is added to the other flux material, and further sintered. The powder is coated with a thermosetting resin.

In these single-sided welding backing fluxes, the sintered body preferably has a particle diameter of 3.0 mm or less and a bulk density of 1.20 to 1.80 g / cc.

The other flux materials other than the welding slag are SiO ₂ : 10 to 45% by mass, Al ₂
O ₃ : 2 to 25% by mass, MgO: 10 to 40% by mass
And SiO ₂ + Al ₂ O ₃ : preferably having a composition of 25 to 50% by mass.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. In order to solve the above-mentioned problems,
As a result of intensive studies, the following findings were obtained. In order to obtain a back bead that is excellent in moisture absorption resistance of the backing flux, has a good shape and appearance, has a stable height, and has no undercut, it is necessary to use a backing flux on the back side of the groove of the material to be welded. It is important to solidify into an appropriate gap and shape, and furthermore, it is necessary to keep the content ratio of the welding slag within a specific range.

The present invention has been made from this point of view. The welding slag of the bond flux is collected, subjected to magnetic separation and pulverization, the particle size is adjusted, and the welding slag powder is used as a raw material powder. It is characterized in that it is added to other flux raw materials so as to have a content of 10% by mass or more based on the total amount of the flux raw material and the welding slag. As a result, resources can be effectively used by reusing the welding slag generated after submerged arc welding, and the back bead has excellent moisture absorption resistance in single-sided welding and a uniform and appropriate extra height. Can be easily formed.

Hereinafter, the backing flux for single-sided welding according to the present invention will be specifically described. As shown in FIG. 1, powder of welding slag is added as raw material powder to powder of flux raw material so as to have a content of 10% by mass or more based on the total amount of flux raw material and welding slag, Granulate using a binder, bake, and apply a thermosetting resin coating. Thereby, the backing flux is manufactured.

Since this backing flux is coated with a thermosetting resin and cannot be dried again before being used in the welding process, the backing flux left in the air for a long time absorbs moisture, It is feared that a gas groove or herringbone is generated in the case. The welding slag of the bond flux used in the submerged arc welding has a low moisture content, has a glassy surface, and has excellent moisture absorption resistance. Therefore, it is effective to apply welding slag as a raw material of the backing flux for the purpose of improving moisture absorption resistance. However, the content of the added welding slag is 10% by mass.
If it is less than 1, the effect of the moisture absorption resistance is not sufficient. Further, in order to form a back bead having a uniform and appropriate extra height, it is necessary to adjust the composition of the flux, and the content of the welding slag is preferably 80% by mass or less.

In producing the backing flux,
The timing of mixing the welding slag and other flux raw materials may be before granulation as shown in FIG. 1 or may be after firing and before resin coating as shown in FIG. Further, after granulation, it may be before firing. In any case, by setting the content of the welding slag within the range described above, a desired good back bead can be obtained.

By limiting as described above, it is possible to obtain a back bead which is excellent in moisture absorption resistance of the backing flux, has a good shape and appearance, has a stable extra height, and has no undercut.

Further, in order to form a more stable back bead, it is preferable that the particle size, bulk density, and other composition of the flux raw material of the raw material powder are defined as follows.

Particle size: 3.0 mm or less, bulk density: 1.2
In order to obtain a back bead having a good shape and appearance of 0 to 1.80 g / cc back bead, a stable height of the back bead, and no undercut, a backing flux on the back side of the groove of the material to be welded is required. Is important to be solidified into an appropriate space and shape. For this purpose, the particle diameter is preferably 3.0 mm or less. 2. Particle size is 3.
If the flux contains more than 0 mm, the solidified shape of the backing flux becomes unstable, and the shape of the back bead tends to meander. This solidification is performed during welding with the coating resin.

The bulk density is 1.20 to 1.80 g.
/ Cc is preferred. The bulk density changes depending on the content ratio of the welding slag or the particle size composition, but if the bulk density is less than 1.20 g / cc, the backing flux cannot obtain an appropriate void, and the back bead shape tends to be unstable. Therefore, the occurrence of undercut is concerned. On the other hand, if the bulk density exceeds 1.80 g / cc, the back bead tends to be convex. When the welding slag is granulated using a flux raw material and a binder, the particle diameter of the raw material powder is preferably 300 μm or less. This bulk density was measured for the backing flux after resin coating and before welding.

The SiO _2: 10 to 45 mass% of other SiO ₂ in the flux in the material is an acidic component, it is effective to adjust the viscosity and melting point of the slag.
When the content of SiO ₂ is less than 10% by mass, the viscosity of the slag at the time of melting is insufficient, and the bead tends to be convex.
On the other hand, when the content of SiO ₂ exceeds 45% by mass, the amount of slag increases, and the excess height tends to be insufficient.

Al ₂ O ₃ : 2 to 25% by mass Al ₂ O ₃ is also an effective component for adjusting the viscosity and melting point of slag. If the content of Al ₂ O ₃ is less than 2% by mass, the viscosity of the slag at the time of melting is insufficient, and the bead tends to be convex. On the other hand, the content of Al ₂ O ₃ is 25% by mass.
If it exceeds, the viscosity of the slag increases, and there is a concern about occurrence of overlap.

MgO: 10 to 40% by mass MgO is a main component for forming slag.
When the content of MgO in the flux raw material is less than 10% by mass, the viscosity of the slag at the time of melting is insufficient, and the bead tends to be convex. On the other hand, if the content of MgO exceeds 40% by mass, the amount of slag tends to increase, and the margin height tends to be insufficient.

[0030]SiO ₂ + Al ₂ O ₃ : 25 to 50% by mass SiO which is preferred for the reasons described above₂And Al₂O₃Success
The quantity was stated. In this case, more preferably,
SiO in flux component₂+ Al₂O₃Content of
Is 25 to 50% by mass. After various studies by the present inventors,
As a result, SiO ₂+ Al₂O₃Back bead shape
Was found to be most important for the stability of
You. SiO₂+ Al₂O₃Less than 25% by mass
If there is, the viscosity of the slag at the time of melting is insufficient, and the bead becomes convex.
Tend to be. On the other hand, SiO₂+ Al₂O₃Content of
Exceeds 50% by mass, the viscosity of the slag increases,
-There is a concern that burlap may occur.

[0031]

EXAMPLES Next, the effects of the backing flux for single-sided welding of Examples which fall within the scope of the present invention will be described in comparison with Comparative Examples which fall outside the scope of the present invention. First, backing flux was adjusted using welding slag having various compositions and a flux raw material that had been previously blended with components, and using this, single-sided submerged arc welding was performed under the welding conditions shown in Table 1 below. Next, the weldability was evaluated by observing the shape of the obtained back bead.

FIG. 3A is a sectional view showing a groove shape of a steel sheet used as a welding base material in the present embodiment, and FIG. 3B is a schematic view showing an electrode arrangement. As shown in FIG.
Two V-shaped grooved portions 2 were formed by preparing two steel plates 1 each having a notch inclined from the upper surface toward the butt end face, and arranging these end faces with each other. Then, as shown in FIG. 4, a backing flux 12 is arranged on the surface of the copper plate 10 as a backing material, and compressed air is blown from the air hose 11 behind the copper plate 10, so that the copper plate 10
After the backing flux 12 was pressed against the groove back surface 3 of the steel plate 1, submerged arc welding was performed from the V-shaped groove portion 2 side with the electrode arrangement shown in FIG. The front flux 16 was arranged on the groove surface side.

As a result, molten metal 14 is generated in the groove, the front flux 16 is melted to form a layer of slag 15, and the backing flux 12 is also melted to form slag 1
3 was formed. Thus, in one-sided submerged arc welding, welding proceeds in a state surrounded by the fluxes 12 and 16.

In this embodiment, an SM400 steel plate having a thickness of 25 mm is used as the steel plate 1, the groove angle of the groove 2 is set to 50 °, the width of the root surface is set to 5 mm, and welding is performed. A wire having two kinds of wire diameters of 4.8 mm and 6.4 mm was used. Further, as the surface flux 16 on the welding surface side, one having a particle size mesh of 10 × 48 specified in JIS Z3352 was used.

The compositions of the steel sheet and the wire used in this example are shown in Tables 2 and 3 below, and the composition of the table flux on the welding surface side is shown in Table 4 below. Tables 5 and 6 show the composition of the welding slag of the bond flux used as the raw material of the backing flux and the composition of the other flux raw materials other than the welding slag. The characteristics of the backing flux produced using the raw materials shown in Tables 5 and 6 are shown in Tables 7 to 10, and the results of the evaluation of the welding workability are shown in Tables 11 and 1.
It is shown in FIG. The composition of the backing flux is an analysis value before resin coating, and other components are Fe
(Total), alloy components and unavoidable impurities.

Next, the evaluation criteria for the welding workability of this embodiment will be described. In the column of "gas groove / herringbone" shown in Tables 11 and 12, when the test welding length is 3 m,
Those with less than one gas groove / herringbone were rated as ◎, and those with one or more gas grooves / herringbone were rated as x.

FIG. 5 is a plan view showing the meandering (fluctuation width) of the back bead, and FIG. 6 is a schematic diagram showing the extra height of the back bead, the undercut depth, and the overlap angle. As shown in FIG. 5, in the column of “back bead meandering” shown in Tables 11 and 12, when the test welding length is 3 m, the case where the variation width of the back bead is 2 mm or less is ◎, and the variation width is 2 mm. Exceed 4
mm or less was evaluated as 、, and the fluctuation range exceeded 4 mm as ×. As shown in FIG. 6, in the column of “back bead convexity” shown in Tables 11 and 12, when the test welding length is 3 m, the extra height of the back bead is 1 to 3 mm, and
When the extra height was more than 3 mm and 5 mm or less, it was evaluated as ○, and when the extra height was more than 5 mm, it was evaluated as x. In the column of "undercut" shown in Tables 11 and 12, when the test welding length is 3 m, those having an undercut depth of 0.2 mm or less are marked as ◎, and the undercut depth exceeds 0.2 and 0. Those having a depth of 5 mm or less were rated as ○, and those with an undercut depth exceeding 0.5 mm were rated as x. Table 11 and Table 12
In the column of "overlap" shown in the above, when the test welding length is 3 m, the overlap angle is 120 to 150 °.
And the overlap angle is 90 ° or more and 12
If the angle is less than 0 °, the overlap angle is 90 °
Less than was rated as ×. In the column of "insufficient extra height" shown in Tables 11 and 12, when the test welding length is 3 m, those with an extra height of 1 to 3 mm are marked with ◎, and the extra height is 0.
Those having a diameter of 5 mm or more and less than 1 mm are marked with a circle, and the height of the surplus is 0.
Those having a size of less than 5 mm were evaluated as x.

[0038]

[Table 1]

[0039]

[Table 2]

[0040]

[Table 3]

[0041]

[Table 4]

[0042]

[Table 5]

[0043]

[Table 6]

[0044]

[Table 7]

[0045]

[Table 8]

[0046]

[Table 9]

[0047]

[Table 10]

[0048]

[Table 11]

[0049]

[Table 12]

As shown in Tables 7 to 12, C1 to
C31 is an example of the present invention, and C32 to C33 are comparative examples. In each of the fluxes C1 to C31 of the examples, welding workability was good, and a back bead having a uniform and appropriate extra height could be formed. Comparative Example C3
In Nos. 2 and C33, the content of welding slag to be added was less than 10% by mass, so that the moisture absorption resistance was poor, and gas grooves and herringbone were generated in the back bead.

[0051]

As described above, according to the present invention, the welding slag generated after submerged arc welding is used as the flux raw material of the backing flux for single-sided welding, and the mixing ratio with the other flux raw materials is determined by the welding slag. Since the raw material powder is specified to be 10% by mass or more, by using this backing flux, a back bead having a uniform and appropriate extra height can be easily formed.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating a method for manufacturing a backing flux for single-sided welding according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating another method of manufacturing a backing flux for single-sided welding according to another embodiment of the present invention.

FIG. 3A is a cross-sectional view illustrating a groove shape of a steel sheet used as a welding base material in the present embodiment, and FIG. 3B is a schematic view illustrating an electrode arrangement.

FIG. 4 is a sectional view showing a one-sided submerged arc welding method.

FIG. 5 is a plan view showing the back bead meandering (fluctuation width).

FIG. 6 is a schematic diagram showing an extra height, an undercut depth, and an overlap angle of a back bead.

[Explanation of symbols]

 1; steel plate 2; V-shaped groove 3; groove back surface 10; copper plate 12; backing flux 14; molten metal 16;

Continued on the front page (72) Inventor Kaoru Hase 100-1 Urakawachi, Miyamae, Fujisawa-shi, Kanagawa F-term in Kobe Steel, Ltd. Fujisawa Works (reference) 4E084 AA03 AA07 AA11 CA19 CA32 DA26 GA02

Claims (5)

[Claims] 1. A welding slag obtained by pulverizing a slag of a bond flux used for submerged arc welding has a content as raw material powder of 10% by mass or more based on the total amount of other flux raw materials and welding slag. Backing flux for single-sided welding, characterized in that it is added in the following manner. 2. A powder obtained by mixing a powder of the welding slag and a powder of the other flux raw material with a binder added, granulated, and then fired. The backing flux for single-sided welding according to claim 1, wherein a thermosetting resin is coated on the powder. 3. The raw material powder of the welding slag is added to the other flux raw material after the binder is added to the other flux raw material, granulated, and before or after firing, and The backing flux for single-sided welding according to claim 1, wherein the sintered powder is coated with a thermosetting resin. 4. The sintered body has a particle diameter of 3.0 mm or less,
The backing flux for single-sided welding according to any one of claims 1 to 3, wherein the bulk density is 1.20 to 1.80 g / cc. 5. A flux material other than the welding slag is SiO ₂ : 10 to 45 mass%, Al
5. The composition according to claim 1, wherein the composition has a composition of ₂ O ₃ : 2 to 25% by mass, MgO: 10 to 40% by mass, and SiO ₂ + Al ₂ O ₃ : 25 to 50% by mass. Backing flux for single-sided welding as described.