JPH07100689A - Bonded flux for submerged arc welding downward facing fillet - Google Patents

Abstract

PURPOSE:To improve the workability in large current high speed welding for a downward facing fillet by containing oxides of Si, Mg, Al and Ti in specified wt.% and CaF1, CO2, Na2O and K2O in a flux. CONSTITUTION:The bonded flux is composed of, by wt.%, 25 to 40% SiO2, 20 to 30% MgO, 16 to 26% Al2O3, 4 to 14% CaO, 0.5 to 5% TiO2, 1 to 5% CaF2, 1 to 10% metal powder, 3 to 8% CO2 (as carbonate) and 0.5 to 5% N2O and/or K2O and satisfied with 5 to 30 (TiO2+ Al2O3)/CaF2 and, further, 0.01 to 1.0% B2O3 is contained. Thus, the bonded flux adequate for submerged arc welding for downward facing fillet of mild steel or high-tensile steel is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bond (sintering type) flux for submerged arc welding, and more particularly to a bond flux having good welding workability when used for downward fillet welding. Suitable for welding high strength steel.

[0002]

2. Description of the Related Art In downward fillet welding, the melt type flux is mainly used because the melt type flux has a higher speed than the sintered type flux. However, the higher the speed, the smaller the bead width, the poorer the shape, and the greater the possibility of cracking.

In order to improve this, a molten flux in which the flux is foamed has been developed. However, the foam type flux has a problem that the bead appearance is deteriorated when welding with a large current. Also, in order to improve efficiency, it is desired to carry out a large current one pass construction even in a thick plate, but in the conventional foam type flux, the melting point of the flux is low, so workability is likely to deteriorate and the current is lowered. I had to do multi-layer welding.

Therefore, it has been desired to develop a flux which is suitable for a large current and has good workability.
Japanese Patent Laid-Open No. 2-280996 discloses a bond flux intended to solve such a problem. However, this flux is for horizontal fillet welding, and when it is applied to high current downward fillet welding, there arises a problem that beads are irregular. This is because the flux designed for horizontal fillet increases the viscosity of the slag to a certain degree in order to ensure isoscelesity, and when it is applied to the downward fillet, the viscosity of the slag is too high and It is presumed that this is because the bead shape becomes irregular due to the substantial amount.

The present invention solves the above-mentioned problems of the prior art and provides a bond flux for submerged arc welding, which has good welding workability in downward fillet submerged arc welding, especially in large current downward fillet welding. It is intended to be provided.

[0006]

The present inventor has conducted various studies on bond flux in order to address the above-mentioned problems. As a result, we have found a bond flux for submerged arc welding that provides excellent welding workability and stable mechanical performance, especially in high current downward submerged arc welding. In particular, the total amount of TiO ₂ and Al ₂ O ₃ and CaF ₂
Focusing on the ratio with the amount, it was found that the workability as downward fillet welding is improved. Also, conventionally, it has been found that CaF ₂ lowers the viscosity of slag, but
It has been found that it is preferable to reduce the amount of aF ₂ added and increase the amount of Al ₂ O ₃ added.

That is, according to the present invention, SiO ₂ : 25-40
%, MgO: 20~30%, Al 2 O 3: 16~26%, C
_{aO: 4~14%, TiO 2:} 0.5~5%, CaF 2: 1~
5%, the metal powder: 1-10%, (included in the form of _{carbonate) CO 2: 3~8%, Na} 2 O and / or K ₂ O: 0.5 to 5
%, And (TiO ₂ + Al ₂ O ₃ ) / CaF ₂ : 5 to
30, satisfies the further B ₂ O ₃ if necessary: is a 0.01% to 1.0%, a downward fillet submerged arc welding bonded flux, characterized in that a composition comprising the gist.

[0008]

The reason for limiting the chemical components in the present invention is as follows.

SiO ₂ : 25-40% SiO ₂ is an acidic component, and is an effective component for adjusting the viscosity and solidification temperature of slag. However, if the content is less than 25%, the viscosity of the welding slag becomes insufficient, which causes meandering of the bead and undercut. On the other hand, if the content exceeds 40%, the basicity of the flux decreases, the oxygen content in the weld metal increases, the toughness deteriorates, the slag removability deteriorates, and a pock mark easily occurs. Therefore, the amount of Si ₂ O is set to 25 to 40%.

MgO: 20-30% MgO is a basic component, is an effective component for reducing [O] in the weld metal, and also has a function as a viscosity modifier. However, if the content is less than 20%, the effect of reducing [O] in the weld metal is small and the toughness is poor. Also, the bead is likely to meander and undercut occurs. On the other hand, 3
If it exceeds 0%, slag seizure is increased, many pockmarks are generated, and flux consumption is increased, which is not preferable. Therefore, the amount of MgO is set to 20 to 30%.

Al ₂ O ₃ : 16 to 26% Al ₂ O ₃ is a neutral component and is an effective component for adjusting the viscosity and solidification temperature of the slag without lowering the basicity of the slag, and a large current. Improves workability during welding. However, if the content is less than 16%, a sufficient effect cannot be obtained. On the other hand, if the content exceeds 26%, the viscosity of the molten slag becomes too high, and a convex bead is easily formed, resulting in poor slag removability. Therefore, the amount of Al ₂ O ₃ is set to 16 to 26%.

CaO: 4 to 14% CaO is a basic component and is an effective component for adjusting the basicity, viscosity and melting point of the slag. However, if the content is less than 4%, not only the basicity is insufficient to increase the oxygen content in the weld metal, but also the viscosity of the slag tends to be insufficient, and the meandering of the beads is likely to occur. On the other hand, 14
%, The slag removability deteriorates, the moisture absorption resistance of the flux itself deteriorates, and pock marks are likely to occur. Therefore, the amount of CaO is set to 4 to 14%.

TiO ₂ : 0.5 to 5% TiO ₂ is an acidic component and is effective as a melting point and viscosity adjusting agent for slag. Furthermore, it is reduced during melting and retained in the weld metal as Ti, which helps improve the impact performance of the weld metal. However, if the content is less than 0.5%, the amount of Ti supplied into the weld metal will be insufficient, and the impact performance of the weld metal will deteriorate. On the other hand, if it exceeds 5%, the slag will seize and the slag releasability will deteriorate rapidly. Therefore, the amount of TiO ₂ is 0.
5 to 5%.

CaF ₂ : 1 to 5% CaF ₂ is a component necessary for maintaining a good bead appearance at the time of high-current welding, and particularly has an effect of keeping the bead flat. However, if the content is less than 1%, a convex bead is formed during high-current welding, and slag delamination becomes worse. On the other hand, if the content exceeds 5%, meandering or undercutting of the bead occurs during high current welding. Therefore, the amount of CaF ₂ is 1 to
5%.

Metal powder: 1 to 10% Metal powder has a function as a deoxidizing agent, an alloying element and the like.
However, if the content is less than 1%, the effect is not recognized. On the other hand, if the content exceeds 10%, the slag will be seized and the releasability will be significantly deteriorated. Therefore, the content of the metal powder is set to 1 to 10%. Various metal powders can be used as the metal powder, and examples thereof include iron powder, ferrosilicon, ferromanganese, and ferrotitanium.

CO ₂ : 3 to 8% CO ₂ component is a very effective component for shielding the atmosphere with CO gas generated during welding, reducing the amount of [N] in the weld metal, and stabilizing it. To generate CO gas,
It is added to the flux in the form of a carbonate such as CaCO ₃ or BaCO ₃ . However, if the content of the CO ₂ component is less than 3%, the effect is not recognized. On the other hand, if the content exceeds 8%, the gas generation amount increases too much, and a pock mark is likely to be generated. Therefore, the content (in terms of CO ₂ ) of the CO ₂ component (included in the form of carbonate) is 3 to 8%.

Na ₂ O and / or K ₂ O: 0.5 to 5% Na ₂ O and K ₂ O are effective as arc stabilizers and viscosity modifiers for slag, especially in high speed downward fillet welding. Since it is an essential component for ensuring arc stability, N
Add one or two of a ₂ O and K ₂ O. But 0.
If it is less than 5%, the stability and concentration of the arc will be deteriorated, and the bead will meander and the slag entrainment will increase. On the other hand, 5%
If it exceeds, the moisture absorption resistance of the flux deteriorates, and pits and pock marks are likely to occur. Therefore, Na ₂ O and K ₂ O
The total amount of 1 type or 2 types is 0.5 to 5%.

(TiO ₂ + Al ₂ O ₃ ) / CaF ₂ : 5-30 TiO ₂ , Al ₂ O ₃ and CaF _{2 all} adjust the viscosity and solidification temperature of the slag, and have good bead appearance and slag releasability. It is as described above that the obtained function is achieved and that each of these components has an optimum blending range. The present inventor examined the mutual relation of each of these components in a preliminary experiment, and found that the welding workability was greatly influenced also by the ratio of (TiO ₂ + Al ₂ O ₃ ) / CaF ₂ . That is, if this ratio is less than 5, the fluidity of the slag becomes too high and the beads meander, and good beads cannot be obtained. On the other hand, if the ratio exceeds 30, the welding workability deteriorates, and especially the bead shape becomes convex and the slag removability deteriorates. Therefore, the ratio of (TiO ₂ + Al ₂ O ₃ ) / CaF ₂ is set in the range of 5 to 30.

Good bead appearance and toughness can be obtained only by controlling the above components, but further good toughness can be obtained by adding B ₂ O ₃ if necessary.

B ₂ O ₃ : 0.01 to 1.0% B ₂ O ₃ is reduced by welding heat and retained in the weld metal as [B] to improve the impact performance of the weld metal. However, if the content is less than 0.01%, the yield [B] in the weld metal is insufficient, and the impact performance improving effect cannot be sufficiently exhibited. On the other hand, if it exceeds 1.0%, the amount of [B] in the weld metal becomes too large, so that hot cracking tends to occur. Therefore, the amount of B ₂ O ₃ is set to 0.01 to 1.0%.

The flux of the present invention consists essentially of the above-mentioned components. However, in addition to the above-mentioned components, a trace amount of components usually used in flux may be added. Such MnO as _{components, BaO, ZrO, Li 2 O} , there is FeO, and the like.

Next, examples of the present invention will be described.

【Example】

Bond fluxes having the compositions shown in Tables 1 and 2 were prepared by a conventional method and subjected to a downward fillet submerged arc welding test. The welding test conditions are as follows.

Steel plate: JIS SM490A (50 mmt) Wire: JIS Z3351 YS-S6 Groove: T-type fillet welding (Fig. 1) Welding condition (leading electrode): Wire diameter ... 4.8 mm Electric current ... 1350 A Electric pressure ... 35V speed… 40cm / min Welding condition (leading electrode): Wire diameter… 6.4mm Current… 1100A voltage… 47V Speed… 40cm / min

The results of an examination of welding workability (bead appearance, shape, slag peeling, slag baking, pits, blow holes, etc.) and mechanical performance of the welded portion are also shown in each table. As is clear from the table, in the examples of the present invention, excellent welding workability can be obtained in the large current downward fillet welding, and the toughness is also good.

On the other hand, Comparative Example No. 1 outside the scope of the present invention.
Nos. 26 to No. 43 are inferior in welding workability. That is,
First, in No. 26 and No. 27, since SiO ₂ was out of the proper range, the bead meandered in No. 26 and a good bead appearance was not obtained, and in No. 27, the slag removability deteriorated.

In No. 28 and No. 29, since MgO was out of the proper range, undercut occurred in No. 28 and pock mark occurred in No. 29, and a good bead appearance was not obtained.

In No. 30 and No. 31, since Al ₂ O ₃ was out of the proper range, the bead was convex and a good bead appearance could not be obtained.

In No. 32 and No. 33, since CaO is out of the proper range, in No. 32, the bead meandered, and No.
In No. 33, a pock mark was generated and a good bead appearance was not obtained.

In No. 34 and No. 35, since TiO ₂ was out of the proper range, a good impact value could not be obtained at No. 34, and the slag was seized at No. 35 and the slag removability deteriorated.

In No. 36 and No. 37, since CaF ₂ is out of the proper range, the bead becomes convex in No. 36, and (TiO ₂ + Al ₂ O ₃ ) / CaF ₂ is out of the proper range. In some cases, the bead meandered, and under No. 37, an undercut occurred and a good bead appearance was not obtained.

In No. 38 and No. 39, since the metal powder is out of the proper range, a good impact value cannot be obtained at No. 38, and at No. 39, (TiO ₂ + Al ₂ O ₃ ) / CaF ₂ Was out of the proper range, and the slag peeling deteriorated.

In No. 40 and No. 41, CO ₂ is out of the proper range. Therefore, in No. 40, the amount of N in the weld metal increases and a good impact value cannot be obtained. Occurred and a good bead appearance was not obtained.

In No. 42 and No. 43, since Na ₂ O and K ₂ O are out of the proper ranges, the bead meanders at No. 42 and pits are generated at No. 43, and a good bead appearance is obtained. I couldn't do it.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

As described in detail above, according to the present invention,
In particular, it is possible to provide a bond flux for submerged arc welding, which has excellent welding workability in high-speed downward fillet welding with large current.

[Brief description of drawings]

FIG. 1 is a view showing a groove shape.

Claims (2)

[Claims] 1. A weight% (hereinafter, the _{same), SiO 2: 25~40%,} MgO: 20~30%, Al 2 O 3: 16~26%, CaO: 4~14%, TiO 2: 0 _{.5~5%, CaF 2: 1~5%} , metal powder: 1-10%, (included in the form of _{carbonate) CO 2: 3~8%, Na} 2 O and / or K ₂ O: 0 A bond flux for downward fillet submerged arc welding, characterized in that the composition contains 0.5 to 5% of (TiO ₂ + Al ₂ O ₃ ) / CaF ₂ : 5 to 30. 2. The bond flux for downward fillet submerged arc welding according to claim 1, further comprising B ₂ O ₃ : 0.01 to 1.0%.