JP2002331390A - Bond flux for submerged arc welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a bead shape and a bead appearance corresponding to the molten flux, and a satisfactory mechanical properties of a deposited metal, in fillet welding using bond flux, in particular high-speed fillet welding. SOLUTION: The bond flux for the submerged arc welding contains as a basic component SiO2 : 40-70 mass%, MnO2 : 5-20 mass%, MgO: 10-30 mass% and Si: 0.5-4.5 mass%, further contains 80 mass% or more of Fe-Si being a metal alloy of an Si raw material whose particle size is not more than 45 μm, and preferably not containing the Fe-Si whose particle size is 75 μm or more. Preferably, the bond flux further contains CaF2 : 1-8 mass% in the basic component. And in the bond flux of the composition started above, the particle size distribution is limited.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bond flux for submerged arc welding, and obtains a weld metal having good bead shape, welding workability and mechanical properties when used in horizontal fillet welding, particularly high-speed fillet welding. Things.

[0002]

2. Description of the Related Art Many of shipbuilding bottoms, steel frames, bridges and the like are welded structures, and many of the welds are horizontal fillet welds. The welding method is performed by gas shielded arc welding or submerged arc welding. At present, these welding methods are properly used depending on the shape of the structure and required performance. In the case of submerged arc welding, the flux used to obtain a good bead shape and bead appearance is often a molten flux.However, it is necessary to obtain a predetermined mechanical performance of the deposited metal or to increase the leg length. Increasing welding efficiency due to heat input is not sufficient.

In view of these points, a bond flux has been studied. For example, a bond flux for multipurpose welding including fillet welding as an application is disclosed in
No. 1,347,788, when the SiO ₂ content is 20 to 27% by mass, a good bead shape and bead appearance required for high-speed fillet welding cannot be obtained, and undercut occurs at a bead end. Is not enough because there is a problem to do.

Japanese Patent Application Laid-Open No. 62-50235 discloses a firing flux for high-speed fillet welding.
SiO ₂ content 25 to 35% by mass, TiO ₂ content 5 to ₂
At 0% by mass, the amount of oxygen given to the arc atmosphere is small, so that the bead shape and bead appearance required for high-speed fillet welding are not as good as melt flux and are insufficient.

Further, Japanese Patent Application Laid-Open No. 9-85488 discloses a molten flux for submerged arc welding capable of obtaining good welding workability and toughness in high-speed welding, but this technique is a molten flux. For structures that require high performance, there is still a problem of not being able to deal with them, which is not sufficient.

[0006]

In fillet welding using a bond flux for submerged welding, particularly in high-speed fillet welding, a bead shape corresponding to a molten flux,
An object of the present invention is to obtain a bead appearance and to obtain good mechanical properties of a deposited metal.

[0007]

SUMMARY OF THE INVENTION The present invention has been made based on the above-mentioned actual situation, and its gist is as a basic component,
SiO _2: 40 to 70 wt%, MnO _2: 5~20 wt%, MgO: 10 to 30 wt%, Si: 0.5 to 4.5
A submerged arc welding bond flux containing at least 80% by mass of M / Si as a Si raw material and Fe-Si as an iron alloy having a particle size of less than 45 μm and not more than 75 μm. Bond welding flux for arc welding. Further, it is a bond flux for submerged arc welding containing the basic component CaF ₂ : 1 to 8% by mass.

In the bond flux having the above composition, particles having a particle size of less than 297 μm are less than 20% by mass, and particles having a particle size of 297 to 500 μm are 35 to 6%.
0 mass%, particles having a particle size of 500 to 840 μm
It is a bond flux for submerged arc welding in which less than 20% by mass of particles having a mass% and a particle size exceeding 840 μm.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the process leading to the present invention and the content of obtaining good results when high-speed fillet submerged arc welding is performed with the bond flux of the present invention will be described in detail. High-speed fillet welding was performed with a conventional bond flux for submerged arc welding in order to grasp the current situation. As a result, uneven beads were formed, and many pits and blow holes were generated. Further, undercut occurred at the end of the bead, and good results could not be obtained.

It can be assumed that the reason for such a result is that the basic components constituting the bond flux are not suitable for high-speed fillet welding. Therefore, the present invention is based on the premise that SiO ₂ and MgO, which are often used as the main components of the molten flux for submerged arc welding, are used as basic components.
generation of gas as a four-component system to which nO ₂ and Si are added,
It has been found that good weld beads and good weldability can be obtained from deacidification and slag formation. In the bond flux of the present invention, MnO _{2 is used} during submerged arc welding.
Will be described in detail.

In general, MnO ₂ is 3 in differential thermal analysis.
There are endothermic reactions. That is, the first endothermic peak occurring at 200 ° C. or lower is caused by dehydration of the attached water, and the second peak observed between 500 and 700 ° C. is 2
An endothermic reaction of MnO ₂ → Mn ₂ O ₃ + O is caused to release oxygen to form Mn ₂ O ₃ . The third peak near 1000 ° C. causes an endothermic reaction of 3Mn ₂ O ₃ → 2Mn ₃ O ₄ + O, and releases oxygen to form Mn ₃ O ₄ . In the present invention, a predetermined amount of oxygen released at the time of secondary and tertiary peaks generated during heating of MnO ₂ is generated at the time of welding to form an arc atmosphere, stabilize the arc, and contribute to good bead formation. .

On the other hand, in the flux production process, 50
In a firing flux or a melting flux fired at a high temperature of 0 ° C. or higher, oxygen is released due to an endothermic reaction of the secondary and tertiary peaks during the production of the flux,
The effect of gas generation by the secondary endothermic reaction during welding cannot be expected. Also, blow holes and pits are prevented from being generated by the deoxidizing action (eliminating the element) of Si mixed in the flux. Furthermore, because the basicity of the slag increases,
The crack resistance is also improved.

Next, representative components used in the present invention will be described. SiO ₂ has a viscous and highly viscous property and affects welding workability and bead shape. If the content is less than 40% by mass, the bead shape becomes an uneven bead, undercuts and pits are generated, and slag removability is deteriorated. On the other hand, if it exceeds 70% by mass, the viscosity of the slag becomes too high, so that defects such as slag entrainment and undercut also occur, and the bead appearance deteriorates. Therefore, S
The amount of iO ₂ is set to 40 to 70% by mass.

MnO ₂ is an indispensable component for high-speed welding due to the above-mentioned action, and improves the meltability and arc stability, welding workability, and bead shape by generating gas due to welding heat of MnO ₂ . Further, there is an effect of improving crack resistance by improving the basicity of the slag. If the content is less than 5% by mass, the above-mentioned effects cannot be expected, the conformity of the bead ends deteriorates, desired mechanical properties cannot be obtained, and good results cannot be obtained. On the other hand, if the content exceeds 20%, the amount of oxygen generated by the endothermic reaction becomes excessively large. Conversely, the arc becomes unstable due to the CO oxidation reaction, and pits and blowholes frequently occur to deteriorate the bead shape. In this case, the MnO ₂ content is set to 5 to 20% by mass because the desired properties cannot be obtained.

MgO has a high melting point and a high viscosity. By adjusting the melting point and the viscosity of the slag, MgO has an effect on the bead shape, particularly the formation of the bead width. If the content is less than 10% by mass, the effect on the viscosity and the melting point does not appear, a sufficient bead width cannot be obtained, and the slag removability deteriorates. Also,
If the content exceeds 30% by mass, the melting point becomes high, and the melting property of the flux is reduced, so that the bead shape is deteriorated. In addition, the undercut and the slag removability are deteriorated because the viscosity is low, so the amount of MgO is set to 10 to 30% by mass.

It is essential that Si is incorporated in an amount of 0.5 to 4.5% by mass.
It is preferable that the thickness is not less than 75 μm. Si has properties of bonding with oxygen generated from MnO ₂ , deacidifying, yielding to the weld metal, and contributing to increasing the toughness of the weld metal. When the content is less than 0.5% by mass, the effect is not recognized. On the other hand, when the content exceeds 4.5% by mass, the deoxidizing effect becomes too sensitive and O ₂ becomes insufficient, so that smallpox is generated and beads are formed. Due to the deterioration of the surface, and S in the weld metal
i becomes excessive and deteriorates toughness. Therefore, the amount of Si is set to 0.5 to 4.5% by mass.

M / Si (metallic Si), Fe-
It is necessary that the Si raw material has a particle size of 45 μm or less of 80% by mass or more and has a particle size of 75 μm or less and does not contain coarse particles. If less than 45 μm is less than 80% by mass, the dispersibility after granulation is not sufficient, so that a stable deoxidizing effect cannot be obtained and undercuts, blow holes and pits are generated. In addition, when a coarse particle of 75 μm or more is contained, the dispersibility is poor as well, and a stable deoxidizing effect cannot be obtained, and undercuts, blow holes, and pits are generated. Therefore, it is essential to mix 0.5 to 4.5% by mass of Si, and it is preferable that the particle size of the Si raw material is less than 45 μm, 80% by mass or more, and that the Si raw material does not contain coarse particles of more than 75 μm.

Since CaF ₂ has low melting point and low viscosity properties, it is added to adjust the melting point and viscosity of slag for bead formation, and partly decomposes during welding to generate F ₂ gas. Adjust the atmosphere of the arc that causes excess oxygen. In other words, when CaF ₂ is contained in the above-mentioned four-component flux composition, it has an effect of adjusting the melting point and viscosity, or has a gas shielding effect by F ₂ gas, which is effective in reducing the amount of oxygen in the deposited metal and increasing the toughness. Component. When the content is less than 1% by mass, the effect is not recognized and the toughness is deteriorated. If the content exceeds 8% by mass, the slag fluidity is not so large, and the bead shape is deteriorated. Therefore, the amount of CaF ₂ is preferably 1 to 8% by mass.

The particle size of the bond flux of the present invention is set to less than 20% by mass for particles having a particle size of 297 μm or less, 35 to 60% by mass for particles having a particle size of 297 to 500 μm, and 5 to 50% by mass.
20 to 40% by mass of particles having a particle diameter of 84 to
It is preferable to adopt a particle size composition not containing 20% by mass or more of particles having a particle size of more than 0 μm, whereby the gas escape is smoothly performed, and a better bead shape and bead appearance can be obtained. The effect of the granularity configuration will be described in detail.

In the total flux, particles having a size of less than 297 μm are limited to less than 20% by mass. If the content is more than 20% by mass, outgassing during welding becomes difficult, and the flux and molten slag are blown up. Because it occurs frequently, the arc becomes unstable. Further, defects such as undercuts and pits are generated due to difficulty in gas escape, so that particles having a size of less than 297 μm are reduced to less than 20% by mass. Also,
The particle size of 297 to 500 μm is 35 to 60% by mass. However, if the content is less than 35% by mass, the bead width cannot be obtained, the adaptation of the bead end deteriorates, and undercut occurs. On the other hand, if the content exceeds 60% by mass, the melting amount of the flux increases, resulting in a convex bead and undercutting. Therefore, particles of 297 to 500 μm are set to 35 to 60% by mass.

Furthermore, particles of 500 to 840 μm
The reason why the content is limited to ４０40% by mass is that if it is less than 20%, an undercut occurs. When the content is more than 40% by mass,
The melting is not uniform because the flux particles are coarse, and the arc becomes unstable, resulting in deterioration of the bead shape and bead appearance. Further, the content of particles exceeding 840 μm is set to less than 20% by mass when the content is 20% by mass.
If it is more than one, the flux particles become coarse, so that the melting is not performed uniformly, and the arc becomes unstable, resulting in a problem of deterioration of the bead shape and bead appearance. Therefore, particles exceeding 840 μm are set to less than 20% by mass.

From the above, the flux particle size was 297
particles having a particle size of less than 20 μm
35 to 60% by mass of 500 μm particles, 500 to 8
A bond flux for submerged arc welding in which particles having a particle size of 40 μm are 20 to 40% by mass and particles having a particle size exceeding 840 μm are less than 20% by mass is preferable. As an example of the method for producing the bond flux of the present invention, a predetermined component, a raw material adjusted to a particle size is blended, wet-mixed using a binder such as water glass, and granulated at 300 to 450 ° C. This is a method of drying and adjusting to a predetermined particle size distribution to obtain a product.

(Examples) Hereinafter, the present invention will be described in more detail with reference to examples. Table thickness 12 mm, width 10 shown in Table 1
JIS G3106 SM4 of 0mm and length of 750mm
90 steel plates were assembled into a T-shape as shown in FIG. 1 and inclined 45 ° with respect to the horizontal plane to assemble a specimen for downward fillet welding. The horizontal fillet weld was set in an inverted T-shape. And
Bond fluxes having various compositions and particle size distributions shown in Tables 2 and 3 were produced by the above-described production method of firing at 400 ° C., and using the welding steel wires shown in Table 4, the fillet shown in Table 5 Welding was performed under welding conditions.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

[Table 3]

[0027]

[Table 4]

[0028]

[Table 5]

The welding results were evaluated by examining the evaluation of arc stability, slag peeling property, bead appearance, bead shape, bead width, and defect. The results were shown in Table 6 for downward fillet welding, and for horizontal fillet welding. The results are shown in Table 7.

[0030]

[Table 6]

[0031]

[Table 7]

The arc stability was evaluated based on the measurement of the fluctuation range of the welding current and the arc voltage during the downward fillet submerged arc welding, the blowing of the flux during the welding, and the like. The good range of welding current is 700A ± 10,
The good range of the arc voltage is 37V ± 1. If all of the evaluations, such as the evaluation of the flux current, the arc current, the arc voltage, etc., can be satisfied, it was judged as good, and the mark was evaluated as good, and even the poor one was marked as x. Evaluation of slag peelability
Good for natural peeling and light peeling
Marks and those requiring banging were marked X. The bead appearance was evaluated as good if there was no weld defect such as undercut and pit and uniform and beautiful bead shape.

The bead shape was evaluated as good if the end of the bead had good conformity and was a concave bead, and the bead shape was uniform with fine creases.
Marked. The bead width was evaluated as good when the length from the upper leg to the lower leg of the bead surface was 12 mm or more, and evaluated as poor when the length was less than 12 mm, and evaluated as poor when less than 12 mm. Defects were evaluated by fillet welding, and those having no welding defects such as undercuts and pits were evaluated as good, and those with at least one defect were evaluated as inferior.

For the evaluation of toughness, a sheet thickness of 20 shown in Table 1 was used.
An impact test piece No. 4 specified in JIS Z 3111 according to the conditions of butt welding shown in Table 5 was prepared using a steel sheet SM490 mm and subjected to an impact test. Test temperature 0 ° C
Were evaluated as good when the absorbed energy was 80 J or more, and poor when the energy was less than 80 J. Nos. Shown in Tables 2 and 3. Nos. A1 to A14 are examples of the present invention. B1
B18 is a comparative example.

In the example of the present invention, no. A1 to A14 both have good arc stability and slag peeling properties in both downward and horizontal fillet welding, and have excellent welding workability. In addition, the bead appearance was beautiful, and the bead edge became a uniform bead shape with good conformability at the bead end and no defect such as a concave bead. Evaluation of toughness is 80-1
The result was stable and high at 00J, which was a very satisfactory result. No. of Comparative Example. B1 to B18 did not satisfy the constituent conditions of the present invention, and had various defects.

No. Since B1 had a low SiO ₂ content, both downward and horizontal fillet welding resulted in uneven beads, and the bead appearance and bead shape were deteriorated. In addition, undercuts and pits occurred, and the slag removability deteriorated. No. B
In No. ₂ , since the SiO ₂ content is large, the viscosity of the slag becomes too high, undercut and slag entrapment occur in both downward and horizontal fillet welding, and slag peelability, bead appearance,
The bead shape has deteriorated. Further, the basicity of the flux decreased, the amount of oxygen in the deposited metal increased, and the toughness deteriorated.

No. Since B3 has a low MnO ₂ content, sufficient penetration cannot be obtained in high-speed welding, and the fitting of the bead end deteriorates in both downward and horizontal fillet welding,
Arc stability, slag peelability, bead shape, and bead appearance deteriorated. Further, the yield of Mn into the deposited metal was lowered, and the required strength was not obtained, so that the toughness was deteriorated.
No. Since B4 has a large MnO ₂ content, the amount of oxygen in the deposited metal increases, and the toughness deteriorates. Further, as the gas component increased, pits were generated in both downward and horizontal fillet welding, and the bead appearance and bead shape were deteriorated.

No. Since B5 had a low MgO content, the melting point and viscosity of the slag could not be adjusted appropriately, the slag removability was deteriorated, and the lower leg of the bead was poorly adapted to horizontal fillet welding, resulting in overlap. In addition, the basicity was insufficient, the amount of oxygen in the deposited metal increased, and the toughness deteriorated. No. In B6, since the MgO content was large, the viscosity of the slag was low, and undercut and slag entrapment occurred in both downward and horizontal fillet welding, and slag peelability, bead appearance, and bead shape were deteriorated.

No. B7 had a low CaF ₂ content, so the melting point and fluidity of the slag could not be adjusted appropriately, and the slag peelability was slightly poor in both downward and horizontal fillet welding. In addition, CaF ₂ generated little F ₂ gas, and the toughness deteriorated due to a decrease in the shielding gas. No. B8 is Ca
Since F ₂ content is high, the slag fluidity is excessively increased to downward, horizontal fillet welding together slag inclusion occurs, slag removability, a bead appearance, bead shape degraded.

In the comparative examples, no. Since B9 had a low Si content, the deoxidizing effect was not obtained, and the bead shape and bead appearance were deteriorated due to the occurrence of undercuts and pits in both downward and horizontal fillet welding. Further, the amount of oxygen in the deposited metal increased, and the toughness deteriorated. No. Since B10 has a large Si content, the deoxidizing effect was excessive, and the toughness was deteriorated due to a drastic decrease of oxygen in the deposited metal in both downward and horizontal fillet welding. In addition, flapping occurred on the bead surface, and the bead appearance was deteriorated.

No. Since B11 contains more than 75 μm in the particle size composition of Si, dispersibility in the flux after granulation is poor, and a stable deoxidizing effect cannot be obtained. As a result, undercuts and pits were generated in both downward and horizontal fillet welding, and the bead appearance and bead shape were deteriorated. No. B12 is less than 80% of the Si particle size composition having a particle size of less than 45 μm. Therefore, the dispersibility in the flux after granulation is inferior, and a stable deoxidizing effect cannot be obtained. This causes undercuts and pits in both downward and horizontal fillet welds,
The bead shape has deteriorated.

No. B13 has a flux particle size composition after granulation of more than 840 μm exceeding 20%, so that the flux particles become coarse and the melting is not performed uniformly.
Bead appearance and bead shape deteriorated. In addition, gas generation became uneven, and undercuts and pits were generated. No. In B14, less than 20% of the flux having a particle size of 500 to 840 μm in the composition of the flux particle size after granulation increased the amount of flux melted, resulting in a convex bead in both downward and horizontal fillet welding, resulting in undercut. This deteriorated the bead appearance and bead shape.

No. B15 has a particle size of 500 to 840 μm in the flux particle size after granulation exceeding 40%, so that the flux particles become coarse and melting is not performed uniformly, so that arc stability, bead appearance and bead shape are deteriorated. did. No. B16 has a flux particle size composition after granulation of 297 to 500 μm, of which 35%
Therefore, the spread of the bead was poor in both the downward and horizontal fillet welding, and the adaptation of the bead end deteriorated. This resulted in an undercut.

No. In B17, the flux particle configuration after granulation exceeds 297 to 500 μm, and the flux melting amount increased, and the downward and horizontal fillet welds became convex beads, resulting in undercut. This deteriorated the bead appearance and bead shape. No. B
18 is 297 in the flux particle size configuration after granulation.
Since those having a diameter of less than μm exceeded 20%, it was difficult to release gas generated during welding, the flux and molten slag increased, and the arc became unstable. In addition, due to the difficulty of gas release, undercuts and pits were generated in both downward and horizontal fillet welding, and the bead appearance and bead shape were deteriorated. In addition, the comparative example No. B1 to B3, B6, B8,
Since B13 to B18 had poor bead shape and the like, impact tests for toughness evaluation were not performed.

[0045]

As described above, according to the bond flux for submerged arc welding of the present invention, fillet welding,
Particularly in high-speed fillet welding, a bead shape and a bead appearance corresponding to a molten flux can be obtained, and welding workability is improved. Also, good mechanical properties of the deposited metal can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a test piece shape and a fillet welding posture of a steel sheet used in an example of the present invention.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Shigeo Oyama 7-6-1, Higashi Narashino, Narashino-shi, Chiba F-term in Nippon Steel Welding Industry Co., Ltd. 4E084 AA03 AA06 AA11 BA04 BA23 CA03 CA23 DA18 EA04 FA06 FA09 GA02

Claims (4)

[Claims] 1. SiO ₂ : 40 to 70% by mass, MnO ₂ :
5 to 20% by mass, MgO: 10 to 30% by mass, Si:
A bond flux for submerged arc welding, comprising 0.5 to 4.5% by mass. 2. The Si raw material is metallic Si and / or Fe
-Si, and the particle size of the Si raw material is less than 45 μm
The bond flux for submerged arc welding according to claim 1, wherein the bond flux is not less than 75% and not more than 75% by mass. 3. The bond flux for submerged arc welding according to claim 1, wherein the bond flux contains CaF ₂ : 1 to 8% by mass. 4. Particles having a bond flux particle size of less than 297 μm are less than 20% by mass, particles having a particle size of 297-500 μm are 35-60% by mass, particles having a particle size of 500-840 μm are 20-40% by mass. The particles having a diameter of more than 840 μm are less than 20% by mass.
A bond flux for submerged arc welding according to any of the preceding claims.