JP6434386B2 - Bond flux for downward fillet submerged arc welding - Google Patents

Description

  The present invention relates to a bond flux for downward submerged arc welding, and particularly has excellent workability when used for downward fillet welding of welded H-shaped steel columns and beams, which are called build H, which is often used for construction and bridges. Further, the present invention relates to a bond flux for downward fillet submerged arc welding that can obtain a weld metal having a bead shape and mechanical performance.

  In recent years, steel plates used in steel structures such as buildings and bridges have a tendency to become thicker, and in order to weld efficiently, submerged arc welding with large heat input is used. In addition, lessons learned from destruction cases such as earthquakes have raised interest in the safety of steel structures in general, and there is a demand for stable mechanical performance of weld metal even when welding with high heat input.

  Welded joints formed by downward fillet submerged arc welding are required to ensure penetration depth and required leg length, bead shape smoothness, and good compatibility between weld metal and base metal. . In recent years, due to the increase in size of structures, in consideration of earthquake resistance and the like, there is a tendency that good mechanical performance of the weld metal is required.

  Conventionally, as the flux for downward fillet submerged arc welding, a melting type flux that can be welded at a higher speed than a bond flux is often used. However, the thickness of the steel material increases the heat input of welding, and the melt type flux has a low melting point of the flux itself, so that the smoothness of the beads becomes poor and the predetermined mechanical performance of the weld metal cannot be obtained.

Accordingly, in consideration of these points, bond fluxes with favorable welding workability and mechanical performance of the weld metal have been studied. For example, Japanese Patent Application Laid-Open No. 11-347788 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2008-161902 (Patent Document 2) have a bond flux that provides excellent weld metal performance with excellent fillability in downward fillet submerged welding. Is disclosed. However, since the bond fluxes of Patent Document 1 and Patent Document 2 have a low SiO ₂ content and a high Al ₂ O ₃ content, a smooth bead shape cannot be obtained in high heat input welding. Moreover, since there is little content of an iron powder, there exists a problem that the amount of welding metals decreases, and also the welding of high heat input is needed and the toughness of a weld metal falls.

Japanese Unexamined Patent Application Publication No. 2010-125508 (Patent Document 3) discloses a technique for obtaining an excellent weld metal with good welding workability in downward fillet submerged arc welding with large heat input. However, since the bond flux of the cited document 3 contains TiO ₂ and the content of Al ₂ O ₃ is large, there is a problem that the bead alignment is discontinuous and the slag peelability is poor.

Japanese Patent Laid-Open No. 11-347788 Japanese Patent Laid-Open No. 2008-161902 JP 2010-125508 A

  An object of the present invention is to provide a downward fillet submerged arc welding bond flux capable of obtaining good welding workability, bead shape and weld metal mechanical performance even in submerged arc welding with high heat input. .

The gist of the present invention is a mass% with respect to the total mass% of the flux in the downward fillet submerged arc welding flux, SiO ₂ : 25 to 45%, CaO: 5 to 15%, MgO: 10 to 30%, Al ₂ O ₃ : 5 to 15%, total of one or more metal fluorides: 1 to 8%, total of one or two kinds of Na ₂ O and K ₂ O: 1 to 5%, metal carbonate CO ₂ conversion value of salt: 2 to 10%, Mn: 1 to 10%, Al: 0.1 to 0.8%, Fe: 5 to 15%, Si: 0.1% or less, the balance Is an inevitable impurity.
_Further, B ₂ O 3: in downward fillet submerged arc welding bonded flux also characterized in that the further contains 0.1% to 1%.

  According to the bond flux for downward fillet submerged arc welding of the present invention, arc stability and slag peelability particularly in downfill fillet welding with high heat input with and without groove processing such as welded H-shaped steel. In addition, it is possible to obtain a high-quality welded portion with high welding efficiency, such as good welding workability such as a bead shape and excellent mechanical performance of the weld metal.

It is a figure which shows the joint shape in the fillet welding of this invention, Comprising: (a) is a case without a groove process, (b) and (c) are the cases with a groove process. It is sectional drawing which shows the groove shape of the welding test board used for the Example of this invention. It is sectional drawing of the test plate after welding which shows the collection position of a Charpy impact test piece.

  The welding method in which the flux of the present invention is used is fillet submerged arc welding. As described above, there is a case where groove processing is performed and a case where groove processing is not performed. FIG. 1 is a view showing a joint shape in fillet welding according to the present invention, where (a) shows a case without groove processing, (b) and (c) show a case with groove processing, and 11 shows a standing shape. A plate, 12 is a lower plate, and 13 and 14 are weld beads. (A) No groove processing in the figure is general fillet welding, and the length d of the welded portion after welding is large. (B) In the figure, the length d of the welded part after welding is reduced by groove processing, and excellent joint performance is obtained such that the fatigue strength can be increased accordingly. (C) The figure further deepens the groove to make the length of the welded portion after welding zero, and is equivalent to butt welding of the K groove. In the present invention, fillet submerged arc welding includes all joint shapes in the range from FIG. 1 (a) to FIG. 1 (c).

The inventors of the present invention conducted various studies on the composition of the bond flux that can produce slag with high fire resistance under high heat input welding conditions, and investigated the effects on welding workability and the mechanical performance of the weld metal.
As a result, arc stability can be obtained by using appropriate amounts of Na ₂ O, K ₂ O and CO ₂ . The bead shape can be obtained by adjusting SiO ₂ , CaO, MgO, Al ₂ O ₃ , metal fluoride, Na ₂ O, K ₂ O, Mn, Al, and Fe. As for slag removability, it was found that a smooth and familiar bead shape can be obtained by adjusting SiO ₂ , CaO, metal fluoride and Al. Furthermore, it has been found that the mechanical performance of the weld metal can be obtained by adjusting SiO ₂ , MgO, metal fluoride, CO ₂ , Mn, Al and Si to appropriate amounts.

  The downward fillet submerged arc welding bond flux of the present invention can be achieved by a synergistic effect of each component composition alone and coexisting, and the component composition of the downward fillet submerged arc welding bond flux of the present invention will be described below. The reason for limitation will be described. The content of each component is expressed by mass% with respect to the total mass of the bond flux for downward fillet submerged arc welding, and when expressing the mass%, it is simply expressed as%.

_[SiO 2: 25~45%]
SiO ₂ made of silica sand, wollastonite, water glass (sodium silicate, potassium silicate) or the like increases the viscosity of the molten slag and affects welding workability, bead shape, and mechanical performance of the weld metal. If the SiO ₂ content is less than 25%, the viscosity of the molten slag is insufficient, the bead shape becomes poor, and bead meandering or undercut occurs. On the other hand, if SiO ₂ exceeds 45%, the viscosity of the molten slag becomes too high, the bead toes overlap and the slag peelability deteriorates. Furthermore, the oxygen content of the weld metal increases and the toughness deteriorates. Thus, SiO ₂ is set to 25% to 45%.

[CaO: 5 to 15%]
CaO using wollastonite, calcium carbonate, or the like as a raw material is an important component for adjusting the melting point and fluidity of molten slag. If CaO is less than 5%, the melting point of the molten slag is low and the fluidity becomes large, and the fit of the bead toe is poor and undercut occurs. On the other hand, if CaO exceeds 15%, the melting point of the molten slag is high and the fluidity is low, the bead height is non-uniform and the slag peelability is deteriorated. Therefore, CaO is 5 to 15%.

[MgO: 10-30%]
MgO using magnesia clinker, magnesium carbonate, or the like as a raw material is an effective component for reducing the oxygen content of the weld metal, and has the property of increasing the melting point and viscosity of the molten slag. If the MgO content is less than 10%, the oxygen content of the weld metal increases and the toughness decreases. Further, the viscosity of the molten slag is insufficient, and bead meandering and undercutting occur. On the other hand, if the MgO content exceeds 30%, the melting point of the flux increases and a sufficient bead width cannot be obtained, and the viscosity of the molten slag also increases, so that the bead toes overlap. Therefore, MgO is 10 to 30%.

_{[Al 2 O 3: 5~15%} ]
Al ₂ O ₃ containing alumina as a main material is an effective component for adjusting the viscosity of molten slag. When Al ₂ O ₃ is less than 5%, the melt slag is insufficient in viscosity, so that undercut is likely to occur. On the other hand, when Al ₂ O ₃ exceeds 15%, the viscosity of the molten slag becomes excessive and the bead becomes convex. Accordingly, _Al 2 _{O 3} is 5 to 15%.

[Total of one or more metal fluorides: 1 to 8%]
Metal fluorides that use fluorite, aluminum fluoride, barium fluoride, magnesium fluoride, etc. as raw materials have the property of lowering the melting point and viscosity of molten slag, and smooth the beads under high heat input welding conditions. It is an effective ingredient to keep. Moreover, the oxygen of a weld metal is reduced and toughness is improved. If the total of one or more metal fluorides is less than 1%, the bead shape is not smooth and the toughness of the weld metal deteriorates. On the other hand, if the total of one or more of the metal fluorides exceeds 8%, the fluidity of the molten slag becomes excessive and undercut is likely to occur, and the slag peelability deteriorates. Accordingly, the total of one or more metal fluorides is 1 to 8%.

[Total of one or two of Na ₂ O and K ₂ O: 1 to 5%]
Na ₂ O and K ₂ O mainly composed of water glass (sodium silicate, potassium silicate) are effective components for improving the stability of the arc and making the bead wave finer by improving the bead appearance. It is. When the total of one or two of Na ₂ O and K ₂ O is less than 1%, the arc is unstable and the bead tends to meander, whereas the total of one or two of Na ₂ O and K ₂ O When it exceeds 5%, undercut occurs. Therefore, the total of one or two of Na ₂ O and K ₂ O is 1 to 5%.

[CO ₂ conversion value of metal carbonate: 2 to 10%]
CO ₂ equivalent values from metal carbonates such as calcium carbonate (CaCO ₃ ) and magnesium carbonate (MgCO ₃ ) have the effect of blocking molten metal from the atmosphere and stabilizing the arc. If the CO ₂ conversion value of the metal carbonate is less than 2%, the arc becomes unstable and the shield becomes insufficient, the N amount of the weld metal increases, and the toughness of the weld metal deteriorates. On the other hand, if the CO ₂ conversion value of the metal carbonate exceeds 10 %, the gas amount becomes excessive and a pock mark is generated. Therefore, the CO ₂ conversion value of the metal carbonate is 2 to 10%.

[Mn: 1 to 10%]
Mn using metal Mn and Fe—Mn as raw materials is an effective component for improving the hardenability of the weld metal and enhancing the strength and toughness. In addition, the bead surface is smoothed. If Mn is less than 1%, the hardenability of the weld metal is insufficient and the toughness is lowered. In addition, a smooth bead shape cannot be obtained. On the other hand, if Mn exceeds 10%, the hardenability of the weld metal becomes excessive, the strength becomes too high, and the toughness decreases. Therefore, Mn is 1 to 10%.

[Al: 0.1 to 0.8%]
Metal Al and Al made from Fe—Al act as a deoxidizer and adjust the viscosity of the molten metal to smooth the bead shape. If the Al content is less than 0.1%, the toughness of the weld metal decreases. Further, the viscosity of the molten metal becomes low, and the wave of the bead becomes rough, resulting in poor slag removability. On the other hand, if Al exceeds 0.8%, the viscosity of the molten metal becomes high and the bead becomes convex. Therefore, Al is made 0.1 to 0.8%.

[Fe: 5 to 15%]
Fe made from iron content of iron powder and iron alloy (Fe—Mn, Fe—Al) as a raw material moves to the molten pool during welding and increases the amount of welding. If the Fe content is less than 5%, the welding amount is insufficient and the welding efficiency is lowered. On the other hand, if Fe exceeds 15%, the bead becomes convex. Therefore, Fe is 5 to 15%.

[Si: 0.1% or less]
Si is an effective component as a deoxidizing component, but in downward fillet welding with high heat input, the amount of dilution of the base material is large, and Si diluted from the base material is sufficient. If the flux Si exceeds 0.1%, the hardness of the weld metal becomes excessive and the toughness deteriorates. Therefore, Si is made 0.1% or less.

[B ₂ O ₃ : 0.1 to 1%]
B ₂ O ₃ mainly composed of borax and boron oxide is reduced by welding heat and yielded as B to the weld metal to improve the toughness of the weld metal. If B ₂ O ₃ is less than 0.1%, the effect of improving toughness cannot be obtained. On the other hand, when B ₂ O ₃ exceeds 1%, hot cracking occurs in the weld metal. Therefore, B ₂ O ₃ is 0.1 to 1%.

The other of the downward fillet submerged arc welding bond flux of the present invention is unavoidable impurities such as FeO, TiO ₂ , MnO, P, and S, both of which promote hot cracking of the weld metal, Preferably as little as possible.

Hereinafter, the effects of the present invention will be described in detail by way of examples.
As shown in FIG. 2, a steel plate having a thickness of 32 mm having the chemical composition shown in Table 1 is a double-sided groove having a web steel plate 1 of 45 ° and a root face r of 16 mm as shown in FIG. Thus, the groove was assembled by bringing the end face of the web steel plate 1 into contact with each other. The length of the test plate was 1000 mm, and the flanged steel plate 2 was tilted by 60 ° with respect to the horizontal so as to be welded downward during welding.

  Combining the wires shown in Table 2 and bond fluxes with various component compositions shown in Table 3, downward fillet submerged arc welding with one electrode on two passes was performed under the welding conditions shown in Table 4.

The evaluation items were the arc stability, slag peelability, bead shape, presence or absence of weld defects, and weld metal toughness.
The slag peelability was evaluated as good if the slag was easily peeled off with a hammer or a chisel and was easily peeled off.

The toughness of the weld metal is as follows: weld metal 3 welded first shown in FIG. 3, weld metal 4 welded later
Among them, Charpy impact test piece 5 (JIS Z 2242 V notch test piece) was sampled around 7 mm below the bead surface of the weld metal welded later, and three Charpy impact tests at a test temperature of 0 ° C. were repeated, and the absorbed energy If the average value of was 50 J or more, it was considered good. The results are summarized in Table 5.

In Table 3 and Table 5, flux symbols F1 to F10 are examples of the present invention, and flux symbols F11 to F24 are comparative examples. Flux symbols F1 to F10 which are examples of the present invention are SiO ₂ , CaO, MgO, Al ₂ O ₃ , one or more of metal fluorides, or one or two of Na ₂ O and K ₂ O. total, CO ₂ conversion value of metal carbonates, Mn, Al, the amount of Fe and Si is at an appropriate amount, the arc is stable, good slag removability, a bead shape is smooth, smooth, undercut Ya There was no weld defect such as overlap, and a good value of the absorbed energy of the weld metal was obtained. Flux symbols F4, F5, and F7 to F9 contained an appropriate amount of B ₂ O ₃ , so that the absorbed energy was 50 J or more, which was a very satisfactory result.

In the comparative example, the flux symbol F11 has a small amount of SiO ₂ , so that the bead snaked and undercutting occurred. Moreover, since there is little Al, the slag peelability was poor and the absorbed energy of the weld metal was low.

Since the flux symbol F12 has a large amount of SiO ₂ , the slag peelability was poor and overlapped. Also, the absorbed energy of the weld metal was low. Although the addition of B ₂ O ₃ because a small amount, the effect of improving the absorption energy of the weld metal is not obtained.

Since the flux symbol F13 has little CaO, the familiarity of the bead toe portion was poor and undercut occurred. Moreover, since Mn is small, the absorbed energy of the weld metal was low.
Since the flux symbol F14 contains a large amount of CaO, the slag peelability was poor and the bead height was non-uniform. Moreover, since the CO ₂ converted value is large, pock marks occurred.

In the flux symbol F15, since there was little MgO, the bead meandered and an undercut also occurred. Moreover, the absorbed energy of the weld metal was low. Furthermore, since there was little Fe, the amount of welding was small.
Since the flux symbol F16 has a lot of MgO, the bead width was narrow and overlapped. _Moreover, since the B 2 _{O 3} is large, crater cracks occurred.

In the flux symbol F17, undercutting occurred because Al ₂ O ₃ was small. Also, since the total of Na ₂ O and K ₂ O was small, the arc was unstable and the beads meandered.
Since the flux symbol F18 has a lot of Al ₂ O ₃ , the bead has a convex shape. Moreover, since there is much Si, the absorbed energy of the weld metal was low.

With the flux symbol F19, the bead shape was not smooth because the total amount of metal fluoride was small. Moreover, the absorbed energy of the weld metal was low. Although the addition of B ₂ O ₃ because a small amount, the effect of improving the absorption energy of the weld metal is not obtained.
In the flux symbol F20, since the total amount of metal fluorides is large, the slag peelability is poor and undercutting occurs.

In the flux symbol F21, since the total of Na ₂ O and K ₂ O was large, an undercut occurred. _Moreover, since the B 2 _{O 3} is large, crater cracks occurred.
Since the flux symbol F22 has a small amount of CO ₂ conversion, the arc is unstable. Moreover, the absorbed energy of the weld metal was low. Furthermore, since there was much Al, the bead became convex.

Since the flux symbol F23 has a large amount of Mn, the absorbed energy of the weld metal was low. Although the addition of B ₂ O ₃ because a small amount, the effect of improving the absorption energy of the weld metal is not obtained.
Since the flux symbol F24 has a large amount of Fe, the bead has a convex shape.

DESCRIPTION OF SYMBOLS 1 Web steel plate 2 Flange steel plate 3 Welded metal initially welded 4 Welded metal welded later 5 Charpy impact test piece 11 Standing plate 12 Lower plate 13, 14 Weld bead d Length of non-welded part r Length of root face

Claims (2)

In the downward fillet submerged arc welding bond flux, the mass% of the total mass% of the flux,
SiO _2: 25~45%,
CaO: 5 to 15%,
MgO: 10-30%,
Al ₂ O _3: 5~15%,
Total of one or more metal fluorides: 1 to 8%,
One or of the sum of Na ₂ O and _{K 2} O: _1~5%,
CO ₂ conversion value of metal carbonate: 2-10%,
Mn: 1-10%
Al: 0.1 to 0.8%,
Fe: 5 to 15%
Containing
Si: Bond flux for fillet submerged arc welding facing downward, characterized in that it is 0.1% or less and the balance is inevitable impurities. _2. The downward fillet submerged arc welding bond flux according to claim 1, further comprising B ₂ O ₃ : 0.1 to 1% by mass% relative to the total mass% of the flux.

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