JP3376377B2 - Flux-cored wire for gas shielded arc welding - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flux-cored wire for gas-shielded arc welding used for welding steel structures, and particularly to a repetitive load such as a ship or a bridge. The present invention relates to a flux cored wire for gas shielded arc welding, which can improve the fatigue strength of a fillet weld which becomes a problem during long-term use of a steel structure and can perform all-position welding. [0002] In the background of recent demands for higher efficiency and labor saving of welding, a flux-cored wire for gas shielded arc welding having a small diameter of 1.0 to 2.0 mm (hereinafter, flux). The cored wire) is widely used because of its advantages such as good welding workability and high efficiency welding. Accordingly, there is an increasing demand for various individual welding performance improvements corresponding to various welding structures to be applied. Conventionally, in a welded structure such as a ship or a bridge having a high fillet weld ratio, measures to improve the fatigue strength of a horizontal fillet weld have been a problem, and the bead toe is ground with a grinder. Dressing bead or T
A method such as re-melting by IG welding is used. In contrast, JP-A-2-99297 and JP-A-3-180
No. 298 and the like propose a flux-cored wire for horizontal fillet welding, but the bead toe shape effective for improving the fatigue strength has not been sufficiently studied. [0004] The present inventors have also disclosed in Japanese Patent Laid-Open No. 4-361876.
Patent application title: Flux-cored wire having composition specified by
A high-fatigue-strength gas shielded arc welding method combining r-CO ₂ gas was proposed. [0005] However, welding with an Ar-CO ₂ gas is not common in Japan, and there is a strong demand for the development of a flux-cored wire that can improve the shape of the bead toe by combining it with an inexpensive CO ₂ gas. In this case, for example, as proposed in Japanese Patent Publication No. 4-55796, it is preferable to use a flux-cored wire that is not exclusively used for horizontal fillet welding but can be used for all-position welding that is versatile at a construction site. SUMMARY OF THE INVENTION The present invention relates to a flux for gas shielded arc welding that has a good horizontal fillet bead toe shape and enables all-position welding even when the shielding gas is CO ₂ gas. It is intended to provide a cored wire. [0007] The gist of the present invention is to provide a flux-cored wire for gas shielded arc welding in which a steel sheath is filled with a flux, and the following components are indispensable with respect to the total weight of the wire. And a flux-cored wire for gas shielded arc welding. TiO _2: 4.5 to 7.0 wt%, Al ₂ O _3: 1.0
To 2.5 weight%, SiO _2: 0.3~1.0 weight%, Z
rO ₂ : 0.3 to 1.0% by weight, iron oxide: 0.1 to 0.
5% by weight, F: 0.03 to 0.15% by weight, S (including outer skin component): 0.010 to 0.045% by weight, Na, K
Of one or two of the following: 0.05 to 0.30% by weight,
Deoxidizing agent (including a skin component): 1.5 to 5.0% by weight. The horizontal fillet bead formed by a conventional TiO ₂ flux cored wire using CO ₂ gas as a shielding gas tends to be convex, and the toe portion is poorly wrapped or uneven. At the toe of the bead which is not familiar with such a base material (steel plate), the stress concentration increases, and the fatigue strength against repeated loads decreases. That is, FIG. 3 shows a steel plate 1 and a horizontal fillet bead 2.
FIG. 4 is an enlarged view of a cross section of the toe shape 3 of FIG. 4. When the radius of curvature ρ and the contact angle θ are reduced, a kind of notch effect is generated in the bead toe, stress is concentrated on the bead toe and fatigue strength is increased. Decrease. [0010] The relationship between the fatigue strength of the horizontal fillet weld and the bead toe shape (radius of curvature ρ and contact angle θ) is affected by the material and thickness of the steel plate to be applied, heat treatment after welding, etc. Although it is not always clear from the results of the study by the present inventors when the above-mentioned Japanese Patent Application Laid-Open No. 4-361876 is proposed, a toe shape that greatly improves fatigue strength has a curvature radius ρ ≧ 1.0 mm. Since it is known that the contact angle θ ≧ 140 degrees is necessary, this was set as the target value. This target value cannot be attained by a conventional flux cored wire made of CO ₂ gas. The method of measuring the radius of curvature ρ and the contact angle θ is to enlarge the cross section of the fillet bead toe by 20 times as shown in FIG. The point B is obtained, an optimum radius of curvature ρ including the point A is obtained from the point A to the point B, and then a tangent line near the point B is drawn to obtain an angle formed with the steel plate, that is, a contact angle θ. Further, the flux cored wire of the present invention is not limited to horizontal fillet welding, and aims to obtain good welding workability in various postures such as vertical and upward. The reasons for limiting each component of the flux-cored wire according to the present invention will be described below. TiO ₂ : 4.5-7.0% by weight TiO ₂ is a main slag forming agent, uniformly envelops the entire bead, adjusts the bead shape and appearance in each welding position, and maintains and stabilizes the arc. Component. If TiO ₂ is less than 4.5% by weight, the amount of slag generated is insufficient, and a sufficient slag encapsulating effect cannot be obtained up to the bead toe. And the contact angle θ becomes smaller. In addition, the slag holding effect of the molten metal, which is indispensable in the upright and upward positions, is insufficient, causing metal dripping, and almost no welding can be performed unless the current conditions are low. On the other hand, if TiO ₂ exceeds 7.0% by weight, the amount of slag generated becomes excessive, and slag accumulates at the toe of the horizontal fillet bead, and the wrap is slightly wrapped. Further, it becomes sensitive to the influence of the adhering moisture and the primer, and bead surface defects such as pits and gas grooves are easily generated. In addition, slag entrapment is likely to occur in vertical fillet welding or in-bevel joint welding. Al ₂ O ₃ : 1.0 to 2.5% by weight Al ₂ O ₃ increases the solidification temperature of the molten slag and has a high viscosity.
In the present invention, the slag forming agent component for adjusting the fluidity is contained in an amount of 1.0% by weight or more in order to particularly improve the shape of the toe portion of the horizontal fillet bead. If the content of Al ₂ O ₃ is less than 1.0% by weight, the horizontal fillet bead becomes round and the toe wraps, and the radius of curvature ρ and the contact angle θ become small. Al ₂
When O ₃ is contained in an amount of 1.0% by weight or more, the resistance to metal dripping can be significantly improved even under a high current condition in the vertical welding. On the other hand, if the content of Al ₂ O ₃ exceeds 2.5% by weight, the solidification of the molten slag is too fast, the slag encapsulation of the horizontal fillet bead becomes mottled, the appearance is poor, the slag peeling property is deteriorated,
The toe shape is also irregular. In vertical and downward welding, slag flows and metal sagging and slag entrapment are likely to occur, and slag removability is poor. SiO ₂ : 0.3 to 1.0% by weight SiO ₂ is also a slag forming component contained for adjusting the solidification temperature, viscosity and fluidity of the molten slag. Si
If O ₂ is less than 1.5% by weight, the solidification temperature of the molten slag is too high and the viscosity is too small, resulting in a convex horizontal fillet bead. In vertical welding, sagging of metal and peeling of slag deteriorate. On the other hand, when SiO ₂ exceeds 1.0% by weight, the solidification temperature is too low, and the toe of the horizontal fillet bead wraps, and the radius of curvature ρ and the contact angle θ are reduced. In addition, metal sagging and slag removability in a vertical or upward position pose problems. ZrO ₂ : 0.3 to 1.0% by weight ZrO ₂ is also a slag forming component for adjusting the solidification temperature, viscosity and fluidity of the molten slag, and smoothes the bead surface in each position welding. Acts to shape the shape.
If ZrO ₂ is less than 0.3% by weight, the solidification of the molten slag is delayed and the molten metal holding effect in vertical or upward welding is insufficient, so that metal dripping cannot be prevented. Further, under high current conditions, the slag encapsulation property is deteriorated, and the shape and appearance are poor. On the other hand, if ZrO ₂ exceeds 1.0% by weight, the horizontal fillet bead is rounded, the conformability with the toe is deteriorated, and the slag peeling property and the porosity are deteriorated. In vertical or upward welding, the metal drips and slag peeling becomes poor. [0019] Iron oxide: 0.1 to 0.5 wt% iron oxide is effective shape of the horizontal fillet bead, especially improving the matching bead toe portion, FeO Therefore, Fe ₂ O
_{3 and the} like are contained in an amount of 0.1 to 0.5% by weight. If the iron oxide is not contained, the affinity with the steel sheet is deteriorated, and the bead toe becomes irregular. On the other hand, when the content exceeds 0.5% by weight, a bead having a short leg length on the standing plate side is insufficient, and metal sagging occurs in a vertical or upward welding. F: 0.03 to 0.15% by weight F is contained in an amount of 0.03% by weight or more for adjusting the viscosity and fluidity of the molten slag and preventing the generation of pores. F is 0.03
When the amount is less than the weight%, the viscosity of the slag is less reduced and the slag is not covered up to the bead toe end, so that the shape of the toe end is not smooth. Further, when a primer-coated steel sheet or a moisture-absorbed steel sheet is welded, pores are likely to be generated. On the other hand, when F is 0.
If the content exceeds 15% by weight, the fluidity of the molten slag becomes excessive and the toe becomes a subordinate bead wrapped, or the slag encapsulating property at the upper end of the bead on the standing plate side is poor, and the appearance and the slag peeling property are poor. Become. Further, since the arc can be narrowed, it becomes difficult to generate slag entrainment and to perform vertical downward welding. As a raw material containing F, alkali metal fluoride, cryolite, or the like can be used. S (including the outer skin component): 0.010-0.
045% by weight S is contained in an amount of 0.010 to 0.045% by weight in order to lower the surface tension of the molten metal, increase the wettability between the bead and the steel sheet, and improve the shape of the toe of the horizontal fillet bead. .
When S is less than 0.010% by weight, this effect is not exhibited. On the other hand, if it exceeds 0.045% by weight, during welding, the molten metal precedes and it is difficult to weld, and the toe portion becomes uneven. In addition, sagging of metal occurs in vertical and upward welding, and crack resistance and toughness in joint welding deteriorate. Note that S is the total amount of the filling flux (addition of iron sulfide, molybdenum disulfide, etc., impurities of each raw material) and the shell component. Total of one or two of Na and K: 0.0
5 to 0.30 wt% Na and K act as arc stabilizers. These one
If the species or the total of the two species is less than 0.05% by weight, the arc becomes coarse and spatter increases. On the other hand, 0.30% by weight
Is exceeded, the arc state becomes unstable, and frequent occurrence of spatter and entrainment of slag tend to occur. As a raw material containing Na and K, these fluorides and oxides can be used. Deoxidizing agent (including a skin component): 1.5 to 5.
0 wt% C (0.01-0.10 wt%), Si (0.2-1.
5% by weight), Mn (1.0 to 4.3% by weight), Al
(1.0% by weight or less), Mg (0.5% by weight or less), Z
R (0.5% by weight or less), etc., in order to secure the mechanical properties of the welded portion and to prevent the occurrence of porosity in the welded portion due to insufficient deoxidation, a total of 1.5% by weight or more including a shell component. To be included. On the other hand, when the deoxidizing agent exceeds 5.0% by weight,
Poor peeling due to slag seizure, poor bead appearance, and excessively high strength degrades cracking resistance. In addition, since the deoxidizing agent forms a slag in addition to acting as a yield alloying agent in the weld metal, it also affects the composition and amount of the molten slag and impairs the effects of the present invention, and therefore, it is preferable to suppress the deoxidizing agent within the range of (). . The reasons for limiting the components contained in the flux-cored wire of the present invention as essential components have been described above. In particular, for improving the toe shape of the horizontal fillet bead, Al ₂ O _{3 is used.}
This is largely due to the synergistic effect of O ₃ and S. 1 and 2 show the effects of Al ₂ O ₃ and S on the bead toe shape, which are extracted from the following examples. This is a measurement result of the shape of the toe portion by performing a horizontal fillet welding test using a 12 mm thick steel plate (SM490B) as a T-shaped fillet test plate. In FIG. 2, as the Al ₂ O ₃ content increases, the radius of curvature ρ and the contact angle θ increase, and the target values of the present invention in which Al ₂ O ₃ is 1.0 to 2.5% by weight are set. It can be seen that this can be achieved when a flux-cored wire is used. However, as shown in FIG. 1, when a flux-cored wire whose S content is out of the limited range of the content of the present invention is used, the bead toe shape does not reach the target value. The effect of improving the bead toe shape by Al ₂ O ₃ of the present invention is that the solidification temperature of the molten slag is increased by containing Al ₂ O _{3 in an amount} of 1.0% by weight or more, and the bead is reduced by the arc force. This is because the toe of the molten pool in the closed state is solidified by pressing it with slag in the solidification process. At this time, S is used in an amount of 0.010% by weight in order to reduce the viscosity of the molten metal and to improve the compatibility with the steel sheet.
This is necessary. Welding the wire at an advancing angle widens the molten pool surface, so that the effects of the present invention can be further exhibited. On the other hand, Japanese Unexamined Patent Publication No.
Improvement of the bead toe shaped for performing the proposed Ar-CO ₂ based gas in JP in the shielding gas, Ar-CO ₂
Because the system gas has a wider arc in the arc than the CO ₂ gas and the blowing force is stronger, the molten pool becomes concave, and at the end, it solidifies as it is by cooling from the steel plate and the bead toe shape becomes better Things. In the flux cored wire for welding in all positions proposed in Japanese Patent Publication No. 4-55796, the toe shape of the horizontal fillet bead is improved by combining the effects of Al ₂ O ₃ and S. The knowledge of the present invention that it is possible is not recognized at all, together with the problem of increasing the fatigue strength. As the other component of the flux-cored wire of the present invention, if the content of MgO is 0.5% by weight or less, it is effective to prevent cutting on the standing plate side and increase the leg length when the leg length is increased. However, if it exceeds 0.5% by weight, metal dripping is likely to occur in vertical or upward welding. An appropriate amount of Ni, Mo, Ni, Mo, etc. to improve the mechanical properties, weather resistance, fire resistance, etc. of the iron powder and weld metal in order to increase the welding amount and improve the arc state and reduce spatter.
Various alloying components such as Cr, Cu, and B; metal carbonates such as CaCO ₃ (0.5% by weight or less) for improving the primer resistance by providing a stirring action for the molten pool; and Bi (for improving slag removability). 0.05% by weight or less). With respect to the steel sheath, mild steel (C: 0.08% by weight or less, Si: 0.3% by weight)
Hereinafter, Mn: 0.5% by weight or less is preferred, but alloy steel (C: 0.07% by weight or less, Si:
0.3 to 1.5% by weight, Mn: 0.5 to 2.5% by weight)
Can also be used. The flux filling rate is preferably in the range of 10 to 22% by weight based on the total weight of the wire from the viewpoint of slag generation and wire productivity. The cross-sectional shape of the wire may be a conventional general shape as shown in FIG. 4, but a seamless type cross-section (c) having no opening in the outer cover is used for dehydrogenation in the manufacturing process. High-temperature intermediate annealing is possible, and there is no moisture absorption of flux inside the wire during use, so it has excellent porosity resistance, and it also has excellent wire feedability and stability of the target position of the wire tip, so it is a stable bead A toe shape is obtained. The diameter of the wire is not particularly limited, but is preferably 1.2 to 1.6 mm in terms of welding efficiency, a general range of leg length, and productivity. The shielding gas can be used to Ar-CO ₂ based gas and Ar gas other than CO ₂ gas, wire composition designed content of deoxidizing agent for intensity adjustment in this case the weld metal to a lower side of the limited range Is preferable. EXAMPLE A mild steel pipe (C: 0.05% by weight, Si:
0.01% by weight, Mn: 0.35% by weight, P: 0.01
2% by weight, S: 0.004% by weight), the wire was drawn by cold working (intermediate annealing for softening and low hydrogenation was performed once) and the flux shown in Table 1 was added. A wire was prototyped. The flux filling rate of the prototype wire is 15% by weight, and the wire diameter is 1.2 mm. Using these prototype wires, a steel plate (SM490B) having a thickness of 12 mm was formed into a T-shaped fillet joint, and under the test conditions shown in Table 2, horizontal fillet (target leg length 5 mm), elevating improvement and elevating downward Welded. As for the toe shape of the horizontal fillet bead, ten cross-sectional macros were sampled at approximately equal intervals from a welding length of about 1 m, measured by the above method, and the average value was obtained. [Table 1] [Table 2] [Table 3] [Table 4] [Table 5] Test No. Nos. 1-3 and No. Nos. 8 to 10 are the cases where the flux-cored wires (W1 to 3 and W8 to 10) according to the present invention are used. There is no problem in the welding workability in each welding position, and the toe shape of the horizontal fillet bead is sampled. In all the macro sections obtained, the target radius of curvature ρ ≧ 1.0 mm and the contact angle θ ≧ 140 degrees are satisfied. On the other hand, Test No. 4
~ 7 and No. 11 to 23 are comparative examples. Test No. 4 and No. 5 is a wire (W4, W
5) Since the amount of Al ₂ O ₃ is too small, the toe portion of the horizontal fillet bead wraps and the target values of the radius of curvature ρ and the contact angle θ cannot be satisfied. Test No. 6 is Al ₂ of the wire (W6)
Due to too much O ₃ , the toes of the horizontal fillet bead were not uniform, and poor slag peeling, slag entrapment, and metal dripping occurred in vertical welding. Test No. In No. 7, the toe shape of the horizontal fillet bead is not improved because the S of the wire (W7) is too small. Test No. 11 is TiO of the wire (W11)
No. ₂ is too small. No. 12 has too much TiO ₂ in the wire (W12), and 13 is a wire (W1
In Test No. 3), the content of SiO ₂ was too small. No. 14 is No. 14 because the wire (W14) has too much SiO ₂ . Fifteen
Is N because the amount of ZrO ₂ in the wire (W15) is too small.
o. In No. 16, since the ZrO ₂ of the wire (W16) was too large, the toe became a convex, wrapped or poorly aligned horizontal fillet bead, and the workability of the vertical welding was deteriorated. Test No. In No. 17, since no iron oxide was added to the wire (W17) and F was too small, the toes of the horizontal fillet bead were not uniform and pits were generated. Test N
o. In No. 18, since the iron oxide of the wire (W18) was too much, the horizontal fillet bead became subscript, the toe wrapped, and slag seizure occurred. In the vertical position, the metal cannot be sagged and welded. Test No. 19 is S of the wire (W19)
Was too large, the toes of the horizontal fillet bead became uneven, and metal dripping occurred in vertical welding. Test No. No. 20 is No. 20 because the alkali metal component (Na, K) of the wire (W20) is too small. 21
Since the alkali metal component of the wire (W21) was too large, the arc became unstable and spatter occurred frequently, and stable welding could not be performed in vertical welding, and metal dripping occurred. Test No. In No. 22, pits were generated because the wire (W22) had too little deoxidizing agent. Test No. In No. 23, since the deoxidizing agent of the wire (W23) was too large, cracks occurred in slag seizure and vertical downward welding. The present invention improves the toe shape of a horizontal fillet bead with an emphasis on the fatigue resistance of a welded structure, and also provides good workability in welding in each position. A flux cored wire for welding is provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing the relationship between S—Al ₂ O ₃ . FIG. 2 is a graph showing the relationship between Al ₂ O ₃ -radius of curvature and contact angle. 3 (a) and 3 (b) are explanatory diagrams of a method of measuring a bead toe shape in horizontal fillet welding. FIG. 4 is a sectional structural view of a flux-cored wire. FIGS. 5A and 5B are explanatory diagrams of target positions of wires in horizontal fillet welding. FIG. 6 is an explanatory diagram of a wire aiming position in a vertical movement and a vertical movement. [Description of Signs] 1 steel plate 2 bead 3 bead toe 4 steel outer skin 5 filling flux

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B23K 35/368

Claims (1)

(57) [Claims 1] A flux-cored wire for gas shielded arc welding in which a steel sheath is filled with a flux, contains the following components as essential components with respect to the total weight of the wire. A flux cored wire for gas shielded arc welding characterized by the following. TiO _2: 4.5 to 7.0 wt%, Al ₂ O _3: 1.0~2.5 wt%, SiO _2: 0.3~1.0 wt%, ZrO _2: 0.3~1. 0% by weight, iron oxide: 0.1 to 0.5% by weight, F: 0.03 to 0.15% by weight, S (including a skin component): 0.010 to 0.045% by weight, Na, K Of one or two of the following: 0.05 to 0.30
% By weight, deoxidizing agent (including a skin component): 1.5 to 5.0% by weight.