JPH07116892A - Metallic flux cored wire for gas shielded arc welding - Google Patents

Abstract

PURPOSE:To obtain an excellent bead shape with a small amt. of the spatters to be generated and good slab removability by specifying the compsns. of the wire and flux and the flux filling rate of the flux cored wire. CONSTITUTION:The content of C in the entire wire (including the flux, sheath and lubricant) of the flux cored wire formed by filling the flux 2 into the metallic sheath 1 is specified to 0.01 to 0.08%. The flux 2 is formed of 60 to 80% Fe (in terms of Fe in iron powder and iron alloy), 10 to 22% Mn+Si, 1.5 to 3.5 Mn/Si, 3.1 to 5% Al+Mg, <=0.65 Mg/Al, 0.2 to 0.7% Na+K+Ca. The flux is also formed of 6.6 to 20% slag forming agent and 0.01 to 0.60% (in terms of Bi) Bi. The flux is filled at 15 to 25% of the entire part of the wire into the wire.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flux-cored wire for gas shield arc welding, and more particularly to a flux-cored wire which has a small amount of spatter, good slag removability and a good bead shape. It is a thing.

[0002]

2. Description of the Related Art Metal-based flux-cored wires have higher welding efficiency, less slag production and continuous multi-layer welding, as compared with titania-based flux-cored wires.
Etc. had excellent characteristics in terms of welding efficiency. On the other hand, there were more spatters than the titania-based flux-cored wire, and there were problems such as poor fillet bead shape (especially horizontal fillet welding).

It is known that the following factors generally affect the workability of the flux-cored wire. (1) Spatter generation amount ・ C amount in wire (C amount contained in hoop, flux, wire drawing lubricant) ・ Arc stabilizer (alkali metal) addition amount ・ Flux filling rate (2) Bead shape ・ Deoxidation In order to solve these problems, in Japanese Examined Patent Publication No. 5-21677, the amount of C in the wire, the amount of deoxidizers Mn, Si, Al, the amount of alkali metal Na,
The amount of K, the amount of slag forming agent, the particle size of flux and the filling rate of flux are regulated.

[0004]

However, in the present invention, since the amount of slag forming agent is small, the deoxidizing agent is few, and the deoxidization of the weld metal is insufficient, the fluidity of the metal is high. Has not been resolved yet. Further, since the metal-based flux-cored wire is subjected to continuous multi-layer welding, there is a problem that seizure of the slag is more likely to occur than the titania-based flux-cored wire, the slag removability is poor, and the workability is reduced. Has not been considered at all.

Improvements in slag releasability have been investigated in JP-A-58-13495, JP-A-59-13955, JP-B-2-14158 and the like. Of these, JP-A-59-13955
Both Japanese Patent Publication No. 2-14158 and Japanese Patent Publication No. 2-14158 improve the slag removability by using Bi in combination with fluoride and other low melting point oxides. Since the flux-cored wire is used by mixing various raw materials, the material cost is high. In order to reduce the cost, it is preferable to reduce the type of flux as much as possible. In the present invention, it has been found that the use of Bi alone is sufficient for the metal-based flux-cored wire.

Further, JP-A-58-13495 discloses a titania-based flux-cored wire to which Bi is added in order to improve the slag removability. In the present invention, since the welding arc phenomenon is different between the titania-based flux-cored wire and the metal-based flux-cored wire, it has been clarified that the knowledge of the titania-based flux-cored wire cannot be directly applied to the metal-based flux-cored wire. That is,
The titania-based flux-cored wire has a flux pole formed in the welding arc because a large amount of oxide having a high melting point is added to the flux. Therefore, Bi, which has a low boiling point, evaporates from this flux pole to form fumes, so it was necessary to add a little excess in anticipation of the amount of evaporation in order to expect the effect of slag separation. However, since the metal flux contains a large amount of metal powder in the flux, the flux pole is shorter than that in the titania system, and the loss due to evaporation is small. Therefore, if the mixture of the slag-based flux-cored wire is directly applied to the metal-based flux-cored wire, there is a risk that the yield of Bi in the weld metal is increased and the mechanical properties of the weld metal are deteriorated. Therefore, in the present invention, by clarifying the appropriate range of Bi in the metal-based flux-cored wire, it is possible to remove the influence on other workability while obtaining good slag removability.

The present invention provides a flux for gas shielded arc welding, which has high welding efficiency and continuous multi-layer weldability, which are features of a metal-based flux-cored wire, has a small amount of spatter, and is excellent in bead shape and slag removability. The purpose is to provide a cored wire.

[0008]

According to the present invention, in a flux-cored wire having a metallic sheath filled with flux, the C content of the entire wire (including flux, sheath and lubricant) is 0.01 to 0.08%. (Wt% per wire, the same shall apply hereinafter), and the flux is Fe (Fe converted value in iron powder and iron alloy): 60 to 80%, Mn + Si: 10 to 22%, Mn / Si:
1.5 to 3.5, Al + Mg: 3.1 to 5%, Mg / Al ≤ 0.65, Na + K + Ca:
0.2 ~ 0.7%, Slag forming agent: 6.6 ~ 20%, Bi: 0.01 ~ 0.60
% (Bi conversion value), and a flux containing 15 to 25% of the whole wire is filled with flux, which is a metal flux-cored wire for gas shield arc welding.

[0009]

Next, as a result of various studies on the spatter generation amount, the slag removability and the bead shape of the metal-based flux-cored wire according to the present invention, the following has become clear. (1) Sputtering amount It was revealed that the amount of C in the wire, the amount of alkali / alkaline earth metal, and the filling rate of the flux are important for the amount of spattering.

(A) Effect of C content in wire C in the wire reacts with oxygen to form CO during welding.
At that time, droplet explosion occurs due to rapid volume expansion due to gasification, and spatter increases. Therefore, in order to reduce spatter, it is necessary to control the CO reaction by C in the wire. (b) Alkali metal and alkaline earth metal content Alkali metal and alkaline earth metal ionize more easily than other elements because of their low ionization voltage. Therefore, the spatter is reduced by stabilizing the droplet transfer accompanying the arc stabilization.

(C) Flux filling rate When the flux filling rate is increased in a wire having the same diameter, the cross-sectional area of the outer cover is reduced. Therefore, at the same current, the current density increases as the filling rate of the flux increases. By making the current density appropriate so that the pinch force can be effectively used, droplet transfer can be made smooth and spatter can be reduced. (2) Slag releasability Generally, the causes of poor slag releasability include slag entrapment, biting into black skin, and slag seizure. When performing continuous multi-layer welding, the heat input to the weld becomes high, and seizure of the slag is likely to occur. Since Bi has a low melting point and boiling point and a high vapor pressure, it has an effect of preventing contact between slag metals and preventing seizure. (3) Bead shape The shape of the weld bead is determined by the fluidity and viscosity of the weld metal and slag.

The amount of Si + Mn, the ratio of Mn / Si, and the amount of Al + Mg act as a modifier for the fluidity and viscosity of the weld metal and slag, and regulate the bead shape by regulating these to adjust the bead shape. be able to. For the above reasons, the components of the metal-based flux-cored wire are limited as described below.

(Reason for limiting components) C amount in wire: 0.01 to 0.08% If the C amount in the wire is less than 0.01%, the arc becomes unstable and the fluttering feeling of the arc increases. In addition, the strength of the wire is insufficient and the wire feeding performance becomes unstable. 0.08%
If it exceeds, the spatter increases due to the explosion due to the CO reaction between the wires C and O in the droplet, and the fume also increases. Therefore, the range of C content was defined as 0.01 to 0.08%. Fe (converted to Fe in iron powder or iron alloy): 60 to 80% When the amount of Fe in the flux is less than 60%, the welding efficiency, which is a characteristic of the metal-based flux-cored wire, decreases. If it exceeds 80%, deoxidizer and arc stabilizer will be insufficient, resulting in increased spatter and defective bead shape. Therefore, the Fe conversion value is
Specified as 60-80%. Si + Mn: 10 to 22% and Mn / Si = 1.5 to 3.5 If the amount of (Si + Mn) in the flux is less than 10%, deoxidation will be insufficient, the fillet bead shape will deteriorate, and defects such as blowholes will occur. As a result, X-ray performance deteriorates. If it exceeds 22%, the strength of the weld metal becomes too high, and the toughness and crack resistance deteriorate. If Mn / Si is less than 1.5, the toughness of the weld metal is impaired, and if it exceeds 3.5, the bead shape tends to be poor and spatter tends to increase, such being undesirable. Therefore, the range of Mn + Si is 10 to 22% and the range of Mn / Si is 1.5.
Specified as ~ 3.5. Al + Mg: 3.1-5% and Mg / Al ≤ 0.65 Acts as a deoxidizing agent together with Si and Mn. If Al + Mg is less than 3.1%, the bead shape will be poor due to insufficient deoxidation. Also,
Since Mg increases spatter due to a rapid oxidation reaction, Mg
The / Al ratio needs to be 0.65 or less. Therefore Al + Mg
Was set to 3.1 to 5%, and Mg / Al was set to 0.65 or less. Na + K + Ca: 0.2-0.7% (Na + K + Ca) When the amount is less than 0.2%, the arc is concentrated and droplet transfer becomes unstable, resulting in increased spatter. If it exceeds 0.7%, the gas generation component increases and the amount of spatter increases. Therefore, the range of Na + K + Ca was defined as 0.2-0.7%.

Na + K + Ca includes addition in the form of oxide, complex oxide or fluoride. Slag forming agent: 6.6 to 20% If the slag forming agent is less than 6.6%, the arc becomes unstable and spatter increases, and the amount of slag decreases and the bead shape becomes poor. However, if it exceeds 20%, the amount of slag increases and the low slag property, which is the characteristic of metal flux-cored wires, is impaired and continuous multi-layer welding becomes difficult. Therefore, the range of slag forming agent was defined as 6.6 to 20%.

The slag forming agent here is SiO ₂ , TiO ₂ , or Al ₂ O.
Oxides such as ₃ , ZrO ₂ , MgO and MnO. Bi: 0.01 to 0.6% If the amount of Bi added is less than 0.01%, seizure of the slag is likely to occur, resulting in poor peelability. If it exceeds 0.6%, the toughness and elongation of the weld metal decrease. Therefore, the range of Bi content was defined as 0.01 to 0.6%. Flux filling rate: 15-25% If the flux filling rate is less than 15%, the amount of spatter increases,
If it exceeds 25%, the wall thickness of the metallic skin decreases and the current density of the wire becomes too high. As a result, the pushing force of the droplets increases, the arc becomes unstable, and spatter increases.
Therefore, the range of the flux filling rate was defined as 15 to 25%.

The wire according to the present invention may be a wire having a sectional shape as shown in FIG. The wire diameter is 1.2mm, 1.6mm, 2.0mm, 2.4mm, 3.
You can select any wire diameter such as 2 mm.

[0017]

[Embodiment] Mild steel is used as the outer shell and
The formulation shown in 1 was used. Then, various metal flux-cored wires (wire diameter: 1.2 mm) showing the C content and flux filling rate of the wire shown in Table 1 were also prepared, and the wire was used to perform welding under the following conditions to produce a spatter. Amount generated,
The slag releasability, bead shape and arc stability were investigated. The results are shown in Table 2.

Polarity: DC reverse polarity Conditions: 300A-33V-40cm / min Shielding gas: 100% CO ₂ 20l / min Projection length: 20mm Welding position: Downward bead-on-plate welding when measuring spatter amount Other horizontal fillets Welding base material: SM-400 (20nmt)

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

[Table 3]

The measurement method and the evaluation method in Table 2 are as follows. Method of measuring spatter generation amount: The sputter repair device shown in FIG. 2 was used. All the spatter generated when welding for a certain period of time in the repair device was collected and measured by the repair device. The measurement time was 1 minute, and the amount generated per minute (g / min) was measured 3 times and the average value was calculated.

Bead shape evaluation method: Horizontal fillet welding was performed and visually observed for bead smoothness, alignment of toes, overlap, and undercut. Good shape, ○; Is x. Evaluation method of slag releasability: When the slag was removed after continuous multi-layer welding and peeled easily, it was rated as ◯, and when peeling was difficult due to slag seizure and the like, it was rated as x.

Arc stability evaluation method: Visually observe the state of arc turbulence that occurs when downward welding is continuously performed for 15 minutes. When arc turbulence does not occur, it is indicated as ○, and when arc turbulence occurs, it is indicated as ×. did. The results of these experiments show the following. (1) Experiments 1 to 9 are examples of the present invention. These wires have the characteristics of metal-based flux-cored wires such as low slag and high welding efficiency, but the amount of spatter is small,
The spatter peelability is good and the bead shape is also good, showing excellent welding workability.

(2) Nos. 10 and 11 have a C content in the wire outside the range of the present invention, and the C content is too small. No. 10 has a weak arc and is unstable, and the C content is too large. No. 11 had many spatters and fumes. (3) No. 12 and 13 have Fe contents outside the scope of the present invention,
No. 12 with a small amount of Fe has a relatively large amount of slag forming agent, and the amount of slag is too large, resulting in poor workability. No.1
In No. 3, the amount of Fe was too large and Si and Mn were relatively insufficient, so that the bead shape was deteriorated.

(4) Nos. 14 and 15 have an amount of (Si + Mn) outside the range of the present invention, and No. 15 with a small amount of (Si + Mn) has a bad bead shape and has pits and blowholes. Defects such as occurred. No. 14 containing too much (Si + Mn) had problems in the toughness, elongation and crack resistance of the weld metal. (5) No. 16 and 17 have Mn / Si outside the scope of the present invention.
In the case where / Si is too small, the toughness of weld metal is poor and Mn /
In No. 17 where Si was too large, the bead shape was poor and spatter and fume increased.

(6) Nos. 18 and 19 have an amount of (Al + Mg) outside the range of the present invention, and an excessively small amount of (Al + Mg) has a bad bead shape, No. 19 with too much Mg) had low crack resistance. (7) No. 20 has a Mg / Al ratio outside the scope of the present invention,
The droplet transfer was not stable and there was a lot of spatter.

(8) Nos. 21 and 22 have an amount of the slag forming agent outside the scope of the present invention, and the amount of the slag forming agent is too small N
At o.21, the arc became unstable and the spatter tended to increase. In No. 22 with too much slag forming agent, there was a tendency that the amount of slag was too large and the efficiency was low and the amount of fumes was large. (9) In Nos. 23 and 24, the amount of Bi added was outside the range of the present invention, and in No. 23 having an excessively small amount of Bi, slag peeling became difficult. In No. 24 with too much Bi, the arc became unstable and spatter increased. Further, the toughness of the weld metal was poor.

(10) Nos. 25 and 26 have an amount of (Na + K + Ca) outside the range of the present invention, and the amount of (Na + K + Ca) is too small.
The arc became unstable and the amount of spatter increased. (N
No. 26, which has an excessive amount of a + K + Ca), had an increased amount of gas components, which caused arc instability and increased spatter. (11) No. 27 and 28 have a flux filling rate out of the range of the present invention.No. 27 having a low flux filling rate increases the amount of spatter, and No. 28 having a too high flux filling rate has an arc. It was unstable.

[0030]

INDUSTRIAL APPLICABILITY As described above, the metal-based flux-cored wire according to the present invention has an excellent bead shape in which the amount of spatter is small, the slag removability is excellent while the characteristics of the wire are low spatterability and high welding efficiency. Is to give.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing cross sections of various flux-cored wires.

FIG. 2 is a side view of a sputtering generation amount measuring device.

FIG. 3 is a plan view of the sputter repair apparatus of FIG. 2 as seen from above.

[Explanation of symbols]

 1. Metallic skin 2. Flux 3. Spatter collection container 4. Welding torch 5. Steel plate 6. Cart 7. Wire feeder 8. Torch cover

Claims (1)

[Claims] 1. In a flux-cored wire obtained by filling a metallic sheath with a flux, the C content of the entire wire (including the flux, the sheath and the lubricant) is 0.01 to 0.
08% (wt% per wire, the same shall apply hereinafter), and the flux is Fe (Fe equivalent value in iron powder and iron alloy): 60-80
%, Mn + Si: 10 to 22%, Mn / Si: 1.5 to 3.5, Al + Mg: 3.1 to
5%, Mg / Al ≤ 0.65, Na + K + Ca: 0.2-0.7%, slag forming agent: 6.6-20%, Bi: 0.01-0.60% (Bi conversion value), and flux for the entire wire. Metal-based flux cored wire for gas shielded arc welding, characterized by being filled with 15 to 25%.