KR101583197B1 - Bonded flux for submerged arc welding - Google Patents

Abstract

There is provided a bond flux for submerged arc welding in which welding workability is good and a welded metal of high toughness is obtained even when welding is performed by narrowing the low temperature steel.
Wherein the bond flux for submerged arc welding is composed of 25 to 45 mass% of MgO, _{5 to} 25 mass% of Al2O3, _{5 to} 25 mass% of CaF2, _{2 to} 10 mass% of metal carbonate, 2 to 10 mass% in total of BaO: 2 to 10 mass%, at least one of metal Si, Si alloy and Si oxide: total of 2 to 10 mass%, at least one of metal Ti, Ti alloy and Ti oxide: And the total content of the metal Al and the Al alloy is not more than 0.1% by mass, and the total content of the metal Al and the Al alloy is not more than 0.1% by mass , The total content of the metallic Si and the Si alloy is 0.3 to 2.0 mass%, and the total Si amount / total Ti amount is 5 to 15.

Description

[0001] BONDED FLUX FOR SUBMERGED ARC WELDING [0002]

The present invention relates to a bond flux used in submerged arc welding. More particularly, the present invention relates to a bond flux for submerged arc welding suitable for low temperature steels mainly used in marine structures, liquefied petroleum gas (LPG) tanks, and the like.

BACKGROUND ART [0002] With the development of the energy industry in recent years, low-temperature steels have been widely used. In marine structures such as cold-water line pipes, LPG tanks, and oil exploration bases in the ocean using low-temperature steel, further improvement of quality is demanded to secure safety and durability. In particular, performance requirements for welds are becoming more stringent, and from the viewpoint of brittle fracture mechanics, high fracture toughness performance is required for welds and welding materials. Representative examples of the evaluation criteria of toughness include a fracture surface transition temperature (vTrs) in a Charpy impact test and a fracture toughness value (CTOD) at a design temperature.

Further, particularly in a structure having an extremely large plate thickness, such as an offshore structure, the construction may be carried out at a narrowed angle for the purpose of reducing the amount of use of the welding material and shortening the working time, Defects such as defective fusion are apt to occur. Therefore, in addition to the above-described fracture toughness performance, the welding material used for these structures becomes important in terms of slag releasability and affinity in the improvement surface (opening surface) from the viewpoint of welding workability.

Conventionally, hand welding and TIG (Tungsten Inert Gas) welding using a covered arc welding rod are widely used in heavy plate welding of heavy structures using low temperature steel. However, in order to improve the welding efficiency, a submerged arc welding material Has been demanded. However, there is a construction problem in the narrow-width welding of the heavy plate by the submerged arc welding, and there is an increasing demand for the submerged arc welding material for low-temperature steel excellent in welding workability.

Specifically, since the slag generated in submerged arc welding is thicker than other welding methods, the slag is buried in the improvement and it is often difficult to peel off. Therefore, in the narrow-width welding work of the thick plate, a grinder treatment is required to improve the shape of the bottom end, or slag inclusion tends to occur easily. Thus, if the improvement is widened to avoid welding defects such as fusion defects, the efficiency is lowered.

On the other hand, the flux for submerged arc welding is roughly classified into a bond flux and a melt flux. Among them, the bond flux is produced by adding water glass to a flux raw material such as a deoxidizing agent and a slag forming agent, granulating it into an appropriate size, and then drying at a temperature of around 500 캜.

The bond flux is characterized in that the partial pressure of steam in the arc atmosphere is lowered by the CO ₂ gas generated by decomposition of the metal carbonate to suppress the amount of diffusible hydrogen in the weld metal. In addition, since the bond flux has a high resistance to moisture absorption and further increases the basicity, it is possible to improve the toughness by reducing the amount of oxygen in the weld metal, so that a weld metal excellent in crack resistance and toughness performance can be obtained. For this reason, it is important that the bond flux is suitable as a welding material for low-temperature steel, and good welding metal performance can be obtained without depending on welding conditions and welding environment.

Thus, the present applicant has proposed a bond flux for submerged arc welding of a low-temperature steel, which is excellent in welding workability and excellent in low temperature toughness. For example, in the bond flux described in Patent Document 1, the amount of oxygen and the amount of nitrogen in the weld metal are suppressed by specifying the kinds and contents of metal oxides, metal carbonates, metal fluorides and the like. In addition, in the bond flux described in Patent Document 2, in addition to the reduction of the amount of oxygen and the amount of nitrogen in the weld metal, the S content is set in a specific range, thereby improving the affinity in the improvement surface and improving the workability of welding.

Japanese Patent Application Laid-Open No. 59-137195 Japanese Patent Application Laid-Open No. 7-256489

The bond flux for submerged arc welding described in Patent Documents 1 and 2 described above can provide a weld metal with good welding workability and excellent toughness. However, in recent years, in a structure using low-temperature steel, further improvement in quality is required from the viewpoint of ensuring safety and durability, and a welding material used therefor is required to further increase the strength of welding metal and improve workability of welding. Particularly, in submerged arc welding of low-temperature steels, there is a demand for a bond flux having excellent slag releasing property in narrowing and excellent welding efficiency in improving the affinity of beads in terms of improvement.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a bond flux for submerged arc welding in which welding workability is good and a welded metal of high toughness is obtained even when welding is performed with a narrow improvement in low temperature steel.

The bond flux for submerged arc welding according to the present invention comprises 25 to 45 mass% of MgO, _{5 to} 25 mass% of Al ₂ O ₃ , _{5 to} 25 mass% of CaF ₂ , a metal carbonate (in terms of CO ₂ ) 2 to 10% by mass, in total of 2 to 10% by mass, CaO and / or BaO: 2 to 10% by mass in total, at least one of Si, Si and Si oxides (In terms of B): 0.05 to 0.3% by mass in total, S: 0.005 to 0.15% in total (at least one of Ti oxide and Ti oxide: 0.3 to 2.0% by mass in total) (Al conversion value) of the metal Al and the Al alloy is regulated to 0.1 mass% or less and the total content (Si conversion value) of the metal Si and the Si alloy is 0.3 to 2.0 mass% (Total Si amount / total Ti amount) of the total content (Si conversion value) of the metal Si, the Si alloy and the Si oxide to the total content (Ti conversion value) of the metal Ti, the Ti alloy and the Ti oxide is 5 to 15 to be.

The bond flux of the present invention may contain 30 to 40% by mass of MgO.

The content of Al ₂ O ₃ may be 10 to 20% by mass.

The content of CaF ₂ may be 10 to 20% by mass.

Further, the ratio (total Si amount / total Ti amount) of the total content (converted value of Si) of metallic Si, Si alloy and Si oxide to the total content (converted value of Ti) of metallic Ti, Ti alloy and Ti oxide is 5 to 10 .

According to the present invention, the affinity of the beads on the slag peeling and the improvement surface in the narrowing improvement is improved, and the low temperature steel can be welded with high efficiency, and a welding metal of higher toughness than the conventional one can be obtained.

1 is a view showing an improved shape of a test piece used in a welding test.

Hereinafter, embodiments for carrying out the present invention will be described in detail. On the other hand, the present invention is not limited to the embodiments described below.

The bond flux according to the embodiment of the present invention is used for submerged arc welding and includes MgO, Al ₂ O ₃ , CaF ₂ , metal carbonate, CaO and / or BaO, metal Si, Si alloy And Si oxide, at least one of metal Ti, a Ti alloy and a Ti oxide, at least one of a metal B, a B alloy and a B oxide, S and a metal Al and Al The total content of the alloy is regulated to be a specific amount or less.

In the bond flux of the present embodiment, the total content of the metallic Si and the Si alloy is 0.3 to 2.0% by mass in terms of Si. In the bond flux of this embodiment, the ratio of the total content (Si conversion value) of the metal Si, the Si alloy and the Si oxide to the total content (Ti conversion value) of the metal Ti, the Ti alloy and the Ti oxide Total Ti amount) is set in the range of 5 to 15.

[MgO: 25 to 45 mass%]

MgO has an effect of reducing oxygen because it functions to suppress the oxygen in the weld metal as a deoxidizer in addition to increasing the basicity. However, when the amount of MgO in the flux is less than 25 mass%, the oxygen reduction effect described above can not be obtained. On the other hand, when the amount of MgO in the flux exceeds 45 mass%, the slag peeling property and bead appearance deteriorate. Therefore, the content of MgO is 25 to 45 mass%. On the other hand, the MgO content is preferably 30 to 40% by mass, whereby the effect of reducing the amount of oxygen in the weld metal, the slag peeling property and the bead appearance can be further enhanced.

[Al ₂ O ₃ : 5 to 25 mass%]

Al ₂ O ₃ acts as a slag forming agent and also has an effect of enhancing the concentration and stability of arc. However, if the amount of Al ₂ O _{3 in the} flux is less than 5% by mass, the arc becomes unstable and welding becomes difficult. On the other hand, if the amount of Al ₂ O _{3 in the} flux exceeds 25 mass%, the amount of oxygen in the weld metal increases and the toughness deteriorates. Therefore, the content of Al ₂ O ₃ is 5 to 25% by mass. On the other hand, the Al ₂ O ₃ content is preferably 10 to 20% by mass, thereby improving the arc stability and increasing the toughness of the weld metal.

[CaF ₂ : 5 to 25 mass%]

CaF ₂ has an effect of improving the affinity and appearance of beads by adjusting the melting point of a commonly known production slag and also reducing the amount of oxygen in the weld metal. However, when the amount of CaF _{2 in the} flux is less than 5% by mass, the above-mentioned effect can not be obtained. On the other hand, if the amount of CaF _{2 in the} flux exceeds 25 mass%, the arc becomes unstable, the bead shape deteriorates, and a fork mark may be generated on the bead. Therefore, the CaF ₂ content is 5 to 25% by mass. On the other hand, the CaF ₂ content is preferably 10 to 20% by mass from the viewpoint of the effect of improving the affinity of the beads by adjusting the melting point of the produced slag, the effect of reducing the amount of oxygen in the weld metal, the arc stability and the bead appearance.

[Metal carbonate (in terms of CO ₂ ): 2 to 10% by mass]

The metal carbonate is gasified by the heat of welding to shield the arc from the atmosphere to reduce the amount of oxygen in the weld metal. However, when the amount of the metal carbonate in the flux is less than 2% by mass in terms of CO ₂ , the above-mentioned effect is not exerted. On the other hand, if the amount of metal carbonate in the flux exceeds 10 mass% in terms of CO ₂ , the peelability of the slag is lowered, and a fork mark is formed on the bead, thereby deteriorating the bead appearance. Therefore, the metal carbonate content is ₂ to 10% by mass in terms of CO ₂ . On the other hand, examples of the metal carbonate added to the bond flux of the present embodiment include CaCO ₃ and BaCO ₃ .

[CaO and / or BaO: 2 to 10 mass% in total]

CaO and BaO increase the basicity as well as MgO and are effective in reducing oxygen in the weld metal. However, when the total content of CaO and BaO is less than 2 mass%, the above-mentioned effect is not exerted, and when the total content of CaO and BaO exceeds 10 mass%, arc stability and bead appearance deteriorate. Therefore, one or both of CaO and BaO are added so that the total amount is 2 to 10 mass%.

[Metal Si, Si alloy and Si oxide (in terms of Si): 2 to 10 mass% in total]

The metal Si and the Si alloy have a deoxidizing effect for suppressing the amount of oxygen in the weld metal, and the Si oxide has a function of adjusting the bead appearance and bead shape as a slag forming agent. However, when the total content (total Si amount) in the bond flux is less than 2% by mass in terms of Si, the deoxidation effect and the effect as a slag forming agent are not exhibited. On the other hand, when the total content (total Si amount) of the metal Si, the Si alloy and the Si oxide exceeds 10 mass% in terms of Si, the amount of oxygen in the weld metal increases and the toughness decreases.

Therefore, in the bond flux of this embodiment, at least one of metal Si, Si alloy and Si oxide is added so that the total content (total Si amount) is 2 to 10% by mass in terms of Si. On the other hand, as a Si alloy to be added to the bond flux according to the present embodiment, for example, Fe-Si or REM (rare earth element) -Ca-Si and the like, as the Si oxide such as SiO ₂ (silica), or Ca ₃ Si ₃ O ₉ (wollastonite).

[Metal Si and Si alloy (in terms of Si): 0.3 to 2.0 mass% in total]

In the bond flux of the present embodiment, the total content of the metal Si, the Si alloy, and the Si oxide is specified along with the total content of the metal Si, the Si alloy and the Si oxide described above. Concretely, the total content of the metallic Si and the Si alloy is set in the range of 0.3 to 2.0 mass% in terms of Si. This is because if the total content of the metal Si and the Si alloy is less than 0.3 mass% in terms of Si, the aforementioned deoxidation effect can not be obtained, and if it exceeds 2.0 mass%, the deoxidation effect is not improved and the toughness This is because the strength becomes excessively high along with the deterioration.

[Metal Ti, Ti alloy and Ti oxide (in terms of Ti): 0.3 to 2.0 mass% in total]

Metal Ti and Ti alloys, like the above-mentioned metal Si and Si alloys, have a deoxidizing effect for suppressing the amount of oxygen in the weld metal, and are also very effective in improving the low-temperature toughness in connection with the miniaturization of the weld metal. On the other hand, the Ti oxide has an effect of improving the appearance and affinity of the bead by adjusting the viscosity and flowability of the slag as a slag forming agent.

However, when the total content (total Ti amount) in the bond flux is less than 0.3% by mass in terms of Ti, the deoxidation effect and the effect as a slag forming agent are not exhibited. On the other hand, when the total content (total amount of Ti) of the metal Ti, the Ti alloy and the Ti oxide is more than 2.0% by mass in terms of Ti, burning occurs on the bead surface and the slag releasability is deteriorated. Therefore, in the bond flux of this embodiment, at least one of metal Ti, Ti alloy and Ti oxide is added so that the total content (total Ti amount) is 0.3 to 2.0% by mass in terms of Ti.

On the other hand, even when the metal Ti and / or Ti alloy is selectively added to the flux and the Ti oxide is not added, the addition amount thereof is in the range of the total Ti amount described above. Examples of the Ti alloy to be added to the bond flux of the present embodiment include Fe-Ti and the like. Examples of the Ti oxide include TiO ₂ (Ruchil) and FeTiO ₃ (Illuminite).

[Total amount of Si / total amount of Ti: 5 to 15]

As described above, the metal Si, the Si alloy, the metal Ti and the Ti alloy have a deoxidizing effect for suppressing the amount of oxygen in the weld metal, and are involved in the slag formation as an oxide by the oxidation reaction during the solidification process. In addition, Si oxide or Ti oxide has an effect as a slag forming agent.

However, when the ratio (total Si amount / total Ti amount) of the total content (converted value of Si) of metal Si, Si alloy and Si oxide to the total content (converted value of Ti) of metal Ti, Ti alloy and Ti oxide is less than 5 , Poor affinity of the bead tip due to lack of Si, and baking of slag due to Ti overhang, which may cause welding defects. On the other hand, if the total amount of Si / total amount of Ti exceeds 15, the deoxidation effect of the weld metal is not sufficiently obtained and the toughness of the weld metal is significantly deteriorated.

Therefore, the ratio (total Si amount / total Ti amount) of the total content (Si conversion value) of the metal Si, the Si alloy and the Si oxide to the total content (Ti conversion value) of the metal Ti, the Ti alloy and the Ti oxide is 5 to 15 . This makes it possible to prevent slag burning on the bead surface while ensuring toughness of the weld metal. On the other hand, the total Si amount / total Ti amount is preferably 5 to 10, whereby the deoxidation effect of the weld metal is improved and the toughness of the weld metal can be improved.

[Metal B, B alloy and B oxide (in terms of B): 0.05 to 0.3% by mass]

The metals B, B alloys and B oxides have the effect of improving the toughness of the weld metal by suppressing the pre-precipitation ferrite produced in the austenite grain boundary during cooling in the weld metal. However, when the total content of the metal B, B alloy and B oxide is less than 0.05 mass% in terms of B, the above-described effect of improving the toughness of the weld metal can not be obtained, and if it exceeds 0.3 mass%, the toughness deteriorates.

Therefore, in the bond flux of this embodiment, at least one of the metals B, B alloy and B oxide is added so that the total content is 0.05 to 0.3 mass% in terms of B. On the other hand, examples of the B alloy to be added to the bond flux of the present embodiment include Fe-B and Fe-Si-B, and examples of the B oxide include B ₂ O ₃ (boron oxide).

[S: 0.005 to 0.15 mass%]

S has the effect of lowering the surface energy of the molten bond and improving the workability of the weld, in particular, the affinity on the improvement surface, thereby adjusting the appearance and shape of the bead. However, when the amount of S in the flux is less than 0.005 mass%, the above-mentioned effect is not exerted and the fatigue strength is lowered. On the other hand, if the S content in the flux exceeds 0.15 mass%, the ductility and toughness deteriorate. On the other hand, S can be added in the form of iron sulfide or the like.

[Metal Al and Al alloy (in terms of Al): 0.1 mass% or less in total]

Metal Al and Al alloys are generally added to the flux as a deoxidizer to inhibit the amount of oxygen in the weld metal. However, in these metal Al and Al alloys, in addition to deteriorating the toughness of the weld metal by forming a coarse Al-based oxide in the weld metal, the oxidation reaction of the metal Si, the Si alloy, the metal Ti and the Ti alloy is inhibited There is also an action of excessively increasing the strength of the weld metal.

Concretely, when the total content of the metal Al and the Al alloy is more than 0.1% by mass in terms of Al, the toughness of the weld metal deteriorates or the strength of the weld metal becomes excessively high. Therefore, in the bond flux of the present embodiment, the total content of the metal Al and the Al alloy is regulated to 0.1% by mass or less in terms of Al

As described in detail above, in the bond flux of the present embodiment, since the composition of the component is in a specific range, and the total content of the metal Si and the Si alloy and the total amount of Si / total amount of Ti are within a specific range, The affinity of the beads on the slag peeling and improved surface is good, and it becomes possible to weld the low temperature steel with high efficiency without defects. Further, by using the bond flux of the present embodiment, it is possible to obtain a weld metal of higher toughness than the conventional one.

Example

Hereinafter, the effects of the present invention will be described in detail with reference to Examples and Comparative Examples of the present invention. In the present embodiment, the welding test in submerged arc welding was carried out using the wires shown in the following Table 1 and the bond fluxes in the examples and comparative examples shown in the following Tables 2 and 3, and the performance was evaluated . On the other hand, the remainder in the wire composition shown in Table 1 is Fe and inevitable impurities. Each of the bond fluxes of Examples and Comparative Examples includes Fe, Na ₂ O, K ₂ O, FeO and Li ₂ O in addition to the components shown in Tables 2 and 3 below.

<Welding Test>

1 is a view showing an improved shape of a test piece used in a welding test. In the welding test, a rolled steel material for welding structure (JIS G3106 SM400B) having a plate thickness of 25 mm was processed by the V improvement shown in Fig. 1 and the welding conditions were set to 500 to 650 A - 26 to 30 V to 30 cpm (wire diameter: Passing temperature: 150 DEG C). Thereafter, a tensile test piece (JIS Z3111 A2) and a Charpy impact test piece (JIS Z3111 V notch) were taken from the weld metal and subjected to various tests.

The "tensile test" was carried out on the basis of JIS Z3111, and the 0.2% proof stress, tensile strength (TS) and elongation (EL) were measured. The &quot; Charpy Impact Test &quot; was also performed based on JIS Z3111, and the Charpy absorbed energy at -60 deg. C was measured. The evaluation of each item in the &quot; tensile test &quot; was passed at 400 MPa or more for a 0.2% proof stress and was rejected at a load of less than 400 MPa. The tensile strength (TS) was in the range of 483 to 655 MPa. In addition, elder (EL) passed 22% or more and less than 22% was rejected. On the other hand, the &quot; Charpy impact test &quot; indicates that the Charpy absorbed energy was 100 J or more, and that less than 100 J was a failure.

At the same time, the welding workability and the oxygen content of the weld metal were also examined, and the flux of which welding workability was poor was stopped by the machine test. The weldability was evaluated for slag peelability, bead appearance, affinity of beads and arc stability. In the evaluation of the &quot; slag releasability &quot;, it was found that the slag was naturally peeled off, the peeled slag was easily peeled off with air chippers, and the other ones (the slag was not peeled off even with air chippers) .

The evaluation of &quot; bead appearance &quot; indicates that the beads were observed with naked eyes, ripples were aligned, no surface defects such as fork marks were observed at all, &amp; cir &amp;, ripples were found and surface defects such as fork marks And those other than those (those having a large number of surface defects such as those having no ripples or fork marks, etc.) were evaluated as x.

Evaluation of &quot; affinity of beads &quot; Even when the beads were visually observed, it was found that the wettability between the weld metal and the base material was good and that the weldability was good, that the wettability of the weld metal and the base material was relatively good, (The weld metal and the base material were poor in wettability and had no affinity) were evaluated as &quot; X &quot;. In the evaluation of the &quot; arc stability &quot;, it was indicated that the welding current was extremely low in vibration, &amp; cir &amp;, the welding current was low in vibration, and the other ones (high welding current was high).

The results of the tensile test and the Charpy impact test were all acceptable and the results of the tensile test and the Charpy impact test were both acceptable "No " in the evaluation of the weldability was evaluated as " ", and the others (those having a failure in the result of the tensile test or the Charpy impact test or X in the evaluation of the weldability) .

On the other hand, the oxygen content of the weld metal was measured by an infrared absorption method. The above results are summarized in Tables 4 and 5 below.

As shown in Table 4, in the No. of Examples of the present invention. The bond fluxes of 1 to 8 showed good welding workability, good weld metal strength (0.2% proof tensile strength), ductility (elongation) and toughness (Charpy absorbed energy).

On the other hand, as shown in Tables 4 and 5, the comparative example No. 1 of the present invention. Bond fluxes 9 to 35 have poor weld metal strength, ductility, toughness or weldability. Specifically, 9 had a MgO content of 49 mass% and exceeded the range of the present invention, so that the peelability of the slag and the bead appearance deteriorated. In addition, 9, the amount of oxygen in the weld metal was large, and the bond flux was low. On the other hand, In the 23-bond flux, the MgO content was less than the range of the present invention at 24% by mass, so that the strength of the weld metal was increased and the toughness was lowered.

No. 10, the amount of Al ₂ O ₃ was 26% by weight, which exceeded the range of the present invention. Therefore, the amount of oxygen in the weld metal was increased to become low in humanity, and in addition, the affinity and appearance of the beads were inferior. On the other hand, Since the bond flux of 24 was less than the range of the present invention of Al ₂ O ₃ of 4 mass%, it was difficult to secure the arc stability and the test was stopped. In addition, 11, the content of CaF ₂ was 26% by mass, exceeding the range of the present invention, so that the arc stability was poor and the affinity and the appearance of the bead deteriorated. On the other hand, The bond flux of 25 was 4% by mass of CaF _{2, which} is lower than the range of the present invention, so that the strength of the weld metal was increased and the toughness was lowered. In addition, The bond flux of 25 also lagged the affinity and appearance of the beads.

The metal carbonate (CO ₂ ) in an amount of 11 mass% exceeds the range of the present invention. 12, the test was stopped because the slag detachment became remarkably difficult and the bundle of fork marks was confirmed. On the other hand, when the amount of the metal carbonate (CO ₂ ) is 1% by mass, the amount of the metal carbonate (CO ₂ ) is less than the range of the present invention. 26, the test was stopped because a defect caused by a defective shield occurred on the surface of the bead. No. 13 had a total content of CaO and BaO of 11 mass% and exceeded the range of the present invention, so that the bead appearance and arc stability deteriorated. On the other hand, 27, the total content of CaO and BaO is 1% by mass, which is smaller than the range of the present invention, so that the strength of the weld metal is increased and the toughness is lowered.

No. 14, the total content of metal Si and Si alloys having a deoxidizing effect exceeded the range of the present invention by 2.2% by mass, so that the strength of the weld metal was increased and the ductility and toughness were lowered. On the other hand, 28, the total content of the metal Si and the Si alloy is 0.2 mass%, which is smaller than the range of the present invention, so that the strength of the weld metal is increased and the toughness is lowered. In addition, 15, the total content of the metal Al and Al alloys having a deoxidizing effect is 0.12 mass%, which exceeds the range of the present invention. Therefore, a coarse Al-based oxide is formed in the weld metal, and the toughness and ductility And the strength was greatly increased.

No. 16, the total amount of Ti was 2.1% by mass, which exceeded the range of the present invention, so that the slag releasability deteriorated. On the other hand, 29, the total amount of Ti is 0.2 mass%, which is smaller than the range of the present invention, so that the strength of the weld metal is increased and the toughness is lowered. In addition, 17, the total amount of Si was 11 mass% and exceeded the range of the present invention, so that the toughness and ductility of the weld metal were lowered and the strength was increased. On the other hand, 30, the total amount of Si is 1% by mass, which is smaller than the range of the present invention, so that the amount of oxygen in the weld metal is increased and the toughness of the weld metal is deteriorated and the strength is greatly increased. In addition, 30, the slag releasability and the affinity of the beads were also inferior.

No. 18, the total amount of Si / total amount of Ti was 19, which exceeded the range of the present invention. Therefore, the amount of oxygen in the weld metal was increased and the toughness was lowered. On the other hand, 31, the total amount of Si / total amount of Ti is 4, which is lower than the range of the present invention, so that the slag releasing property and the affinity of the bead are deteriorated and the strength of the weld metal is also increased. In addition, 19, the total content (in terms of B) of the metal B, B alloy and B oxide was 0.37 mass% and exceeded the range of the present invention. On the other hand, 32, the total content (in terms of B) of the metal B, B alloy and B oxide is 0.03 mass%, which is less than the range of the present invention, so that the weld metal becomes low in phosphorus and the strength increases.

No. Since the bond flux of 20 was 0.160% by mass and S exceeded the range of the present invention, the weld metal was low in ductility, low in strength, and showed an increase in strength. On the other hand, 33 had a S content of 0.004 mass% which was smaller than the range of the present invention, resulting in deterioration in welding workability, slag peeling property, and appearance and affinity of beads. In addition, In the 33 bond flux, the weld metal was low ductility and strength was increased. No. 21, the total Si amount / total Ti amount is 25, and the No. 22, the total amount of Si / total amount of Ti was 16, which exceeded the range of the present invention, so that the toughness of the weld metal deteriorated. In addition, The increase in weld metal strength was also observed in the 21 bond flux.

No. 34, the total amount of Si / total amount of Ti is 4, which is lower than the range of the present invention, and the content of MgO is 46% by mass and exceeds the range of the present invention. Therefore, the slag peeling property, the appearance and affinity And the welding workability was poor. In addition, 35, the total amount of Ti exceeded the range of the present invention by 2.8 mass%, and the total amount of Si / total amount of Ti was 1, which is lower than the range of the present invention. This No. The bond flux of 35 showed deterioration not only in the slag releasability but also in the overall welding workability, because the affinity of the bead and the arc stability were also inferior.

From the above results, it was confirmed that the bond flux of the present invention was able to obtain a weld metal having a good weldability and a high tensile strength even when the low temperature steel was welded with narrowing.

Claims (5)

MgO: 25 to 45 mass%
Al ₂ O ₃ : 5 to 25 mass%
CaF ₂ : 5 to 25 mass%
Metal carbonate (in terms of CO ₂ ): 2 to 10% by mass,
CaO and / or BaO: 2 to 10 mass% in total,
At least one (in terms of Si) of the metal Si, the Si alloy and the Si oxide: 2 to 10 mass% in total,
At least one (converted to B) of the metal B, B alloy and B oxide: 0.05 to 0.3 mass% in total,
S: 0.005 to 0.15 mass%
In addition,
When the total content (Al conversion value) of the metal Al and the Al alloy is less than 0.1% by mass
In addition,
The total content (in terms of Si) of the metal Si and the Si alloy is 0.3 to 2.0 mass%
The ratio (total Si amount / total Ti amount) of the total content (Si conversion value) of the metal Si, the Si alloy and the Si oxide to the total content (Ti conversion value) of the metal Ti, the Ti alloy and the Ti oxide is 5-15 ego,
The total content (in terms of Ti) of the metal Ti, the Ti alloy and the Ti oxide is 0.4 to 0.9 mass%
Bond flux for submerged arc welding. The method according to claim 1,
And MgO is 30 to 40% by mass. The method according to claim 1,
Al ₂ O ₃ is 10 to 20% by mass. The method according to claim 1,
And CaF ₂ is 10 to 20% by mass. The method according to claim 1,
(Total Si amount / total Ti amount) of the total content (Si conversion value) of the metal Si, the Si alloy and the Si oxide to the total content (Ti conversion value) of the metal Ti, the Ti alloy and the Ti oxide is 5 to 10 Features bond flux for submerged arc welding.

Images