JPH0122079B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a flux-cored wire for arc welding, and more particularly to a flux-cored wire that exhibits excellent bead shape, bead appearance, undercut resistance, and slag releasability in downward fillet welding and horizontal fillet welding. Gravity welding has traditionally been widely used for fillet welding of shipbuilding, steel frames, bridges, etc., but as welding technology advances, there is a tendency to shift to semi-automatic and fully automatic welding, which have higher welding efficiency. Wires used in this case include gas shield wires and non-gas wires, and among them, gas shield wires have good workability in fillet welding. However, this type of commercially available wire is often oriented toward versatility, and its components are adjusted to provide average performance in all welding positions, such as downward, vertical, and upward welding. As the practical use of on-site fillet welding progresses, various problems as shown below have been pointed out. The bead does not stretch. Undercuts are likely to occur. The beads are not aligned properly. The bead shape tends to be convex or concave. Overlap is likely to be formed at the bead toe. In particular, when there is a gap of about 3 mm or more in the fillet joint, the above-mentioned tendency becomes noticeable, and repair welding is required to a greater or lesser extent. The present inventors focused on the above-mentioned circumstances, and even when applied to fillet joints with a relatively wide gap of about 3 mm or more, the welds have good bead shape, bead appearance, and undercut resistance. We have been conducting research to provide a flux-cored wire specifically for fillet welding that can provide The present invention was completed as a result of such research, and its composition is _TiO2 : 35 to 70% (wt%:
(same below), SiO ₂ : 5 to 30%, Al ₂ O ₃ : 1 to 5%,
Contains Mn: 10 to 30% and organic matter: 0.2 to 6% as essential components, and further contains one or more divalent metal oxides selected from CaO, MnO, and MgO for a total of 0.5%.
The gist lies in the fact that the flux containing ~15% by weight is filled in the mild steel outer skin in an amount of 10~25% based on the total weight of the wire. The reason for setting the above component composition in the present invention will be explained below. TiO ₂ : 35-70% TiO ₂ is a component that adjusts the fluidity and encapsulation of the slag. If it is less than 35%, the encapsulation of the slag is insufficient and the bead becomes convex and undercuts tend to occur. Become. On the other hand, if it exceeds 70%, the slag coverage becomes excessive and tends to form a two-stage bead, and the slag covers the molten pool too much, making it difficult to keep the continuous rod speed constant. SiO ₂ : 5-30% SiO ₂ is a component that adjusts the viscosity of the slag and the strength of the arc. If it is less than 5%, the arc force will be weak and the viscosity of the slag will be small, so the slag coverage will not be stable. Beads become uneven. On the other hand, if it exceeds 30%, the viscosity of the slag becomes excessive and the arc force also becomes excessive, leading to frequent undercuts and an increase in the amount of spatter. Al ₂ O ₃ : 1-5% Al ₂ O ₃ has the effect of forming a spray arc to make the bead waves finer and more uniform.
If it is less than 5%, these effects will not be effectively exhibited, while if it exceeds 5%, droplet transfer will become unstable and the waves of the beads will become rough and irregular. Mn: 10-30% Mn acts as a deoxidizing agent and is an essential component to improve the porosity resistance of weld metal. If it is less than 10%, pores will occur due to insufficient deoxidation, and if it exceeds 30%, Pores are created by the agent. Organic matter: 0.2-6% Pulp floc, starch, gore gum, cellulosin, etc. are used as the organic matter, and have the effect of stabilizing arc spraying and improving bead alignment and undercut resistance. If it is less than 0.2%, these effects will not be exhibited effectively, while if it exceeds 6%, the arc spraying will become unstable, the bead will become uneven, the undercut resistance will deteriorate, and the amount of spatter will increase. do. Flux-cored wire, which is obtained by filling a casing (sheath) formed from a mild steel strip with a flux containing the above five essential components, effectively exhibits the features of each of the above components, and has a gap of about 3 mm or more. Even when applied to welding fillet joints that have a . By the way, the fillet welded joints encountered at actual welding sites are not only simple fillet joints in which a lower plate and a vertical plate are assembled at right angles, but also fillet joints in which a lower plate and a vertical plate are assembled at an acute angle, and fillet weld joints in which a lower plate and a vertical plate are assembled at an acute angle. There are quite a few fillet joints with rust, and when welding such fillet joints, slag removability is extremely important. Therefore, we conducted further research on measures to improve slag removability. It is generally believed that the releasability of slag is controlled by the difference in thermal expansion and cooling contraction of the slag, the size of the slag density, and the like. Therefore, the inventors of the present invention particularly focused on the slag density among the above-mentioned controlling factors, and considered increasing the releasability of the slag by reducing the slag density. As a result, two selected from CaO, MnO and MgO were found in the above-mentioned flux.
If one or more types of valent metal oxides (hereinafter also referred to as metal oxides) are included in a total of 0.5 to 15%,
It was confirmed that the produced slag became porous and the slag density decreased, and that the peelability of the slag could be significantly improved. These effects are not exhibited effectively when the amount of the metal oxide is less than 0.5%;
If it exceeds this, the viscosity of the slag becomes too low, the encapsulation becomes unstable, and the beads become irregular. Although there are many other metal oxides, as a result of experiments, only the three metal oxides mentioned above showed an outstanding effect on improving slag removability. It is also possible to substitute some or all of the above metal oxides with metal carbonates and convert them into metal oxides by decomposition due to welding heat and mix them into the slag, but when blending as carbonates, the amount If it exceeds 3.5%, the amount of spatter will increase rapidly, so it should be kept below 3.5%. The flux-cored wire of the present invention is manufactured by filling a mild steel casing with the flux having the above-mentioned composition according to a conventional method, and the amount of flux filled is 10 to 25% of the total weight of the wire. must be selected from the range. However, if the flux filling amount is less than 10%, the absolute amount of generated slag will be insufficient, and the slag will not be encapsulated and will become unstable, resulting in irregular beads. while 25%
If the amount exceeds 1, the amount of slag produced becomes too large, resulting in a two-stage bead, or the slag covers the molten pool too much, making it difficult to maintain a constant rod operating speed. Although the present invention is roughly constructed as described above, by strictly specifying the component composition of the flux, even when applied to a fillet joint with a slight gap, it is possible to improve the bead shape, appearance, and under-under resistance. A high quality welded part with good cuttability etc. was obtained. In addition, by incorporating appropriate amounts of specific metal oxides (including carbonate forms) into the flux, slag removability can be greatly improved, even on sharp fillet joints or rusted fillet joints. Can be welded with good workability. Further, the flux-cored wire of the present invention can contain CO ₂ , (CO ₂ +Ar), (CO ₂ +O ₂ ),
It can be used not only for gas-shielded arc welding using a shielding gas such as (Ar+O ₂ ), but also for non-gas arc welding, and has great practical value for automatic or semi-automatic welding. Next, an experimental example of the present invention will be shown. Experimental Example 1 A flux cored wire of 1.6 mmφ was manufactured by filling a mild steel casing with the flux having the composition shown in Table 1 so that the flux ratio was 15 to 16%, and a welding experiment was conducted under the following conditions. I did it. [Welding conditions] Welding current: 350A, DC reverse polarity Welding voltage: 34V Shielding gas: 100% CO ₂ , flow rate 25/min or no shielding gas Welding speed: 50cm/min Welding position: Horizontal fillet welding Test steel plates and joints Shape: 2 paint coated steel plates (30μm wash primer coated, 12mm
Gap using
A 3.2 mm T-shaped fillet joint was formed (see Figure 1). The results are summarized in Table 1. The criteria for workability evaluation in the table are as follows. ◎: Extremely good 〇: Good △: Slightly poor ×: Poor

【table】

[Table] From Table 1, the following can be considered. (1) A-1 to A-8 are comparative examples lacking any of the present invention, and some defects appear as shown below. A-1: Due to insufficient TiO ₂ and too much organic matter, the arc force is strong, the bead becomes slightly convex, and undercuts occur frequently. A-2: Due to excess TiO ₂ and lack of organic matter,
The arc force is weak and there are few sputters, but the bead becomes irregular and becomes a two-stage bead. A-3: Due to insufficient SiO ₂ and too much Mn, the arc force is somewhat weak, and the fluidity of the slag increases, resulting in poorly aligned beads and a concave shape.
Moreover, due to excess deoxidizing agent, many pores are formed on the bead surface. A-4: Too much SiO ₂ and not enough Mn, resulting in strong arc force, and poor slag envelopment, resulting in frequent undercuts. Moreover, there are many pores on the bead surface due to insufficient deoxidation. A-5: Due to insufficient Al ₂ O ₃ and too much TiO ₂ , the arc was unstable and the beads were very poorly aligned. A-6: Because there are too many Al ₂ O ₃ and SiO ₂ , the arc is very strong and the transfer of the droplets is unstable. As a result, not only spatter occurs frequently, but also undercuts occur. A-7: Contains an appropriate amount of metal oxide.
Due to the lack of TiO ₂ , slag removability is hardly improved. A-8: The amounts of all other essential components except the metal oxide satisfy the requirements, but because the metal oxide is too large, the bead shape deteriorates and the beads become irregular. A-9: Although the requirements for metal oxides are met
Due to the lack of SiO ₂ and too much Mn, the arc force is somewhat weak, the beads are poorly aligned, and there are many pores on the bead surface due to excessive deoxidation. Slag removability is also not good. A-10: Although the requirements for metal oxides are met,
Because SiO ₂ is excessive and Mn is insufficient, the arc force is strong and stability is poor. Moreover, there are many pores on the bead surface due to insufficient deoxidation. Slag peeling is also not good. A-11: Although the amount of MgO added is sufficient, the amount of TiO ₂ is excessive and the organic matter is insufficient, so the arc force is weak and there are few spatters, but the beads become irregular and become two-stage beads. Slag removability is also not good. (2) Next, (B-1) to (B-6) are TiO ₂ ,
This is a reference example that satisfies the requirements for the addition of SiO ₂ , Al ₂ O ₃ , Mn, and organic substances, but lacks the requirements for the addition of metal oxides, and the bead shape, undercut resistance, and arc stability are all good. Although there is almost no problem with slag removability, there is still room for further improvement. (3) On the other hand, (C-1) to (C-14) are examples that meet the requirements of the present invention, and because a stable spray arc can be obtained, there are very few spatters and no undercuts occur. In addition, since the viscosity of the generated flag is optimal, the slag is well covered, and fine, well-aligned, flat beads can be obtained. Furthermore, since the slag is made porous by blending an appropriate amount of metal oxide, the slag removability is also extremely good. An example of non-gas welding is shown at the bottom of Table 1 (2), and good results were obtained as in the case of shield gas welding. However, compared to the examples of the present invention, the reference examples still have room for improvement in terms of slag releasability. In addition, reference photos 1 to 5 have the basic composition B-4 in Table 1 (1) and the amount of Al ₂ O ₃ was changed (adjustment of the numerical value by increasing or decreasing Al ₂ O ₃ was done by adjusting TiO ₂ ). ) shows the bead appearance when Al ₂ O ₃ is 1
If it is less than 0.8%, the bead will become uneven, and if it exceeds 5% (5.2%, 5.5%), the alignment of the lower legs of the bead will deteriorate, and there will be a tendency for the bead to become thin and undercut to occur. In contrast to this
Al ₂ O ₃ in the range of 1 to 5% (1.2%, 4.8%)
The bead alignment is extremely good and no defects such as undercuts are observed. Since the present invention is constructed as described above, it exhibits excellent bead shape, bead appearance, and undercut resistance, especially in downward fillet welding and horizontal fillet welding, and also exhibits extremely excellent slag removability. A flux-cored wire is obtained.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a fillet joint employed in an experimental example.

Claims (1)

[Claims] 1 _TiO2 : 35-70% by weight, _SiO2 : 5-30% by weight,
Contains _Al2O3 : 1 to 5% by weight, Mn: 10 to 30% by weight, and organic matter: 0.2 to ₆ % by weight as essential components,
Furthermore, a flux containing a total of 0.5 to 15% by weight of one or more divalent metal oxides selected from CaO, MnO, and MgO is filled into the mild steel outer skin in an amount of 10 to 25% by weight based on the total weight of the wire. A flux-cored wire for arc welding that is characterized by: