JPH0150519B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a low-hydrogen coated arc welding rod with improved welding properties, and more particularly to a low-hydrogen coated arc welding rod that exhibits properties such as welding arc spray transfer and spatter. Low-hydrogen coated arc welding rods (hereinafter simply referred to as low-hydrogen welding rods) provide weld metal with good mechanical properties and crack resistance, so they are widely used as welding materials for thick plates and areas with large binding forces. has been done. However, it has been pointed out that it is less efficient than general welding rods such as illuminite and lime titania. The reason for this is said to be not only the difference in coating composition, but also the difference in the shielding gas generated from the coating. In other words, the composition of the shielding gas generated in general welding rods is mainly composed of H ₂ , H ₂ O, CO, etc., resulting in good arc stability, whereas low-hydrogen welding rods contain CO, CO, etc. Since CO ₂ occupies the mainstream, there is a tendency for the arc to become unstable. In addition, low-hydrogen welding rods have the disadvantage that the droplets become larger and tend to exhibit globulular migration and short-circuit migration, and the amount of spatter generated per rod length increases, which significantly impedes welding workability. . The present invention was made in consideration of this situation, and aims to provide a low-hydrogen welding rod that can realize spraying of droplet transfer and reduction of spatter. . The low-hydrogen welding rod of the present invention that has achieved the above object is one in which a flux component consisting of a slag forming agent, a gas generating agent, etc. is applied to a steel core wire together with a bonding agent, and the flux is SiO ₂ Contains: 1 to 25% (weight%, same below) TiO ₂ : 0.5 to 20% Carbonate: 12 to 60% Metal fluoride: 1 to 25%, and further atomized Fe-Mn: 1 to 13% Atomized Fe -Si: The key point is to use one or more of 3 to 23% of the atomized powder, and at least 55% of the total atomized powder is composed of fine particles that have passed through 60 meshes. _SiO2 , _TiO2 , _CaCO3 , _CaF2 , _MgCO3 ,
A low-hydrogen welding rod coating composition containing BaCO ₃ and the like in a range partially overlapping with the above range is known, for example, from Japanese Patent Publication No. 42673/1983. Also, atomized alloy steel powder (e.g. Fe-Mn, Fe-Si, Fe
For example, Japanese Patent Publication No. 54-8341 (Japanese Patent Application No. 48-80903) discloses that a general coated arc welding rod can be made by coating the periphery of an alloy steel core wire with a coating material containing Ni, etc.).
known by. However, the low-hydrogen welding rod disclosed in the former publication is based on the knowledge that the presence of CaF ₂ lowers the melting point of molten slag and increases the amount of fume generation. The key point is to make _CaF2 more than twice (weight ratio) as _CaF2 . However, as a result, the problem of reduced welding workability due to high melting point slag occurred, and SiO ₂ , BaCO ₃ ,
Since the blending amount of each component of MgCO ₃ is adjusted to find a compromise point, there is a drawback that the degree of freedom in selecting flux raw materials is reduced, and the problem of stabilizing the arc and reducing spatter, which is the problem of the present invention, is There are no notable results and no reports have been made. On the other hand, the invention described in the latter publication takes advantage of the fact that atomized alloy steel powder has a spherical shape,
It improves the adhesion of the coating material by improving the slipperiness of the coating material during painting work on welding rods.As for the relationship with arc stability, microcracks in the coating material may cause arc breakage due to falling off, etc. It was merely a matter of prevention. On the other hand, the present invention has a composition ratio of TiO ₂ and CaF ₂ ,
Alternatively, it is an attempt to improve welding workability without restricting the freedom of raw material selection regarding the type of carbonate, etc., and in particular, improves the droplet transfer state by using atomized Fe-Mn or atomized Fe-Si. The effect is to stabilize the arc and reduce spatter. To this end, we have found that the particle size structure of all atomized powder plays an important role, and based on these comprehensive considerations, we have completed the present invention. Therefore, in this specification, the explanation will start from the points related to atomized powder and granules. Fe-Mn and Fe-Si are general-purpose deoxidizers in low-hydrogen coatings for welding rods. However, the present inventors reexamined its properties, types, amounts, etc. from various angles, and found that Fe-Mn powder produced by the atomization method (regardless of water atomization or gas atomization). and Fe-Si in the range of 1 to 13% for the former and 3 to 23% for the latter, and that at least 55% of the total atomized powder is composed of fine particles that have passed through 60 meshes. It was found that this is extremely important in making the droplet transfer state during welding into spray transfer and in suppressing the occurrence of spatter. That is, a flux component having the composition shown in Tables 1 and 2 is mixed with a fixing agent, and this is applied to the outer periphery of a mild steel core wire to form a prototype welding rod (4.0
mmφ×400mm) was manufactured. As shown in Figure 3,
A test plate (400 mm x 60
mm ^w × 19 ^t ) 2 was placed on the specimen, and bead-on-plate welding was performed in the length direction while maintaining an 80° forward tilted position (AC, 180A). When the amount of spatter scattered on the copper plate 1 was measured and the relationship with the type and content of Fe--Mn and Fe--Si was determined, the results shown in FIGS. 4 and 5 were obtained. The amount of scattered spatter was expressed as the total weight of the welding rod per unit consumption length (cm) (the same applies hereinafter).

【table】

[Table] As is clear from these results, the amount of spatter collected is remarkable in the products containing atomized Fe-Mn or atomized Fe-Si (marked with ●) compared to the normally pulverized product (marked with ○). is decreasing. However, when the content of atomized Fe-Mn is less than 1% and the content of atomized Fe-Si is less than 3%, not only is the effect of reducing the amount of spatter generated insufficient, but the former also causes poor toughness of the weld metal. Since the latter causes additional problems such as the generation of blowholes due to insufficient deoxidation, the lower limits were set at 1% or more for the former and 3% or more for the latter. On the other hand, when the former exceeds 13%, the weld metal becomes hard and its cracking resistance decreases, and when the latter exceeds 23%, the toughness of the weld metal decreases and the viscosity of the generated slag increases, causing severe irregularities on the bead surface. remains. Therefore, upper limits were set for the former at 13% or less and for the latter at 23% or less. Furthermore, Table 3 is
This is a graph showing the relationship between the blending amount of Fe--Mn and Fe--Si and welding workability, and the basic components of the coating material are: CaCO ₃ and MgCO ₃ : 50%, SiO ₂ : 2%, TiO ₂ : 2%, CaF ₂ : 15%, others: 2-29%. Also, Figure 1 shows (A-1) to (A-) in the same table.
Figure 2 shows the absorbed energy (vEo: Kg-m) when using (B-1) to (B-6). In other words, (A-1) has a large amount of spatter due to a small amount of atomized Fe-Mn, and (A-6) has a large amount of spatter due to a small amount of atomized Fe-Mn.
The strength and hardness were excessive due to the large amount of Mn.
(B-1) has a large amount of spatter due to a small amount of atomized Fe-Si, and (B-6) has a low toughness due to a large amount of atomized Fe-Si. Furthermore, (A-2) to (A-5), (B
-2) ~ (B-5), (C-1) ~ (C-4), (D
-1) to (D-4) are examples that satisfy the present invention.

[Table] Since the amount of Fe alloys such as Fe-Ni and Fe-Mo is originally limited (for example, 2% or less), they have little effect on reducing arc spray and spatter. However, the inventors of the present invention were not satisfied with this, and as a result of further studies on the transfer state of droplets and the amount of spatter generated, the following findings were found. That is, since the particle shape of atomized Fe--Mn, atomized Fe--Si, etc. is spherical unlike a normal pulverized product, the voids between the particles are relatively small and constant. Therefore, the process in which the coating melts due to arc heat and the process in which it melts and transfers to the base metal side becomes extremely smooth, resulting in the above-mentioned spray transfer form. However, if the particle size distribution of the atomize varies greatly, Not only will the effect be unstable, but problems will also arise when applying the coating. Table 4 shows the welding test results when changing the particle size distribution of all atomized powder and granules, where 55% or more of all atomized powder and granules are composed of fine particles that have passed through 60 meshes. In (C.1 to 5), the transfer of the droplets was spray-like and the amount of spatter generated was significantly small, and the object of the present invention was almost completely achieved. On the other hand, for those that do not satisfy these conditions (C 6 to 8), the transfer of the droplets is discontinuous, and may cause instantaneous explosive transfer, leading to frequent spatter and poor arc concentration. There was a flaw in it that made it worse. In addition, some coating loss was observed in C-4 to C-5, and if we were to try to avoid this problem, the particles that passed 60 meshes but did not pass 200 meshes would account for more than 40% of the total atomized powder. It was concluded that those occupying (C.1 to 3) are the most suitable.
In other words, as the fineness of the atomized powder increases, spatter decreases and transfer of droplets becomes more stable, but the density of the coating becomes excessive and the paint coating becomes more likely to fall off. On the other hand, if the number of coarse grains increases, the porosity in the coating material becomes excessive, resulting in poor arc concentration and frequent occurrence of spatter. The conditions for the welding test in Table 4 are as follows, and the amount of spatter generated was measured according to the method shown in FIG. <Welding conditions> Test plate: SM50 (12mm ^t × 75mm ^w × 450mm Test rod: 4.0mm〓 × 400mm Welding current: 150 to 170A Welding position: Downward bead-on-plate welding (horizontal fillet and vertical fillet)

[Table] Next, components other than atomized Fe-Mn (Fe-Si) will be explained. SiO ₂ :1~25% It plays a major role as a slag forming agent, but 1
If it is less than 25%, the slag will be too encapsulated and the waveform of the bead will be distorted, while if it exceeds 25%, the slag will be too encapsulated and the slag will easily bite into the bead. TiO ₂ : 0.5-20% Gives a beautiful luster to the bead appearance, but if it is less than 0.5%, the effect will not be achieved, and if it exceeds 20%, the slag will become very dense and pass through, resulting in poor peelability. . Carbonate: 12-60% It is a gas generating agent and is mixed as carbonate of Ca, Mg, Ba, Sr, etc. If it is less than 12%, the amount of gas generated will be small and blowholes may occur due to insufficient shielding. On the other hand, if it exceeds 60%, the slag becomes highly basic, weakening the arc blowing and causing a decrease in the melting rate. Metal fluoride: 1 to 25% A component that adjusts fluidity by adjusting the slag melting point, and is usually added as CaF ₂ , AlF ₃ , NaF, etc., but if it is less than 1%, this effect is not achieved. The slag becomes more viscous and tends to form convex beads. On the other hand, if it exceeds 25%, the fluidity of the slag will be too high and a good bead shape will not be obtained. In addition to the above-mentioned components, commonly used components in coating materials such as alloying agents (Cu, Ni, Cr, Mo, Fe-Ti, Fe
-Al, Mg, etc.), slag forming agents (Al ₂ O ₃ , MgO,
CaO, ZrO ₂ , MnO, etc.), oxidizing agents (FeO, Fe ₂ O ₃
etc.), but iron powder in particular has the function of increasing welding efficiency and is listed as one of the recommended components. However, if more than 45% of iron powder is added, the weld metal tends to drip, especially in vertical position welding, so the upper limit is set at 45%. The coating component of the present invention is a composition that is selectively blended according to the above description, and a fixing agent, preferably an inorganic fixing agent (e.g., SiO ₂ -K ₂ O-H ₂ O, SiO ₂ -
An aqueous solution of Na ₂ O―H ₂ O, SiO ₂ ―K ₂ O―Na ₂ O―H ₂ O, etc.) is added and kneaded. After this is applied to the outer periphery of the steel core wire, moisture is released as completely as possible by high-temperature firing. Since the low hydrogen-based coated rod of the present invention is constructed as described above, it is possible to maintain the transfer of droplets in a spray state and to significantly reduce the amount of spatter generated. Next, embodiments of the present invention were described. A fixing agent was added to the flux components shown in Table 5 and kneaded, and this was coated on a steel core wire to a diameter of 4.0mm〓×
A 400 mm welding rod was prototyped, welding was performed under the conditions shown in Table 6, and the welding work characteristics and amount of spatter were measured. The results are shown in Table 7.

【table】

【table】

【table】

[Table] As shown in Table 5, in the invention examples P.1 to 8, all the conditions of the invention are satisfied, so as shown in Table 7, good results were obtained in all items. It is being On the other hand, each of Comparative Examples S.1 to S.12 did not satisfy any of the conditions of the present invention, and therefore only inconvenient results were obtained. First, in S-1 and S-2, the blending ratio of SiO ₂ is inappropriate, so the encapsulation of the slag becomes unstable and the bead shape is poor. Since S.3 contains too much TiO ₂ , the slag becomes dense and the releasability decreases. S.4,
Since No. 5 has an inappropriate carbonate content, blowholes occur in the weld metal in S.4, and arc concentration becomes poor in S.5. Also S・6, 7
Because the content of metal fluoride is inappropriate, S.6
In S.7, a convex bead was formed, and in S.7, slag entrainment occurred. S・8 Fe-Mn and Fe-Si
is a normally crushed product (the former is equivalent to JIS-G2301, the latter is equivalent to JIS-G2301)
(equivalent to JIS-G2302), the transfer of droplets was globular, and the amount of spatter was not reduced. Since S-9 had a low content of atomized Fe--Mn, the spray transfer of droplets was unstable and the spatter reduction rate was low. S・10 is an example in which both atomized Fe-Mn and atomized Fe-Si are low, and not only does spatter not decrease, but
A blowhole occurred in the weld metal. S.11,
In No. 12, the amount of atomized Fe-Si was inappropriate, so blowholes occurred in S.11, and unevenness was formed on the bead surface in S.12. In S-13, the particle size structure of the atomized powder was inappropriate, so the transfer state of droplets became discontinuous, which could cause instantaneous explosive transfer, which also contributed to reducing the amount of spatter. There weren't many.

[Brief explanation of drawings]

Figures 1 and 2 are graphs showing the effects of atomized Fe-Mn and Fe-Si, Figure 3 is a cross-sectional view showing the implementation status of test welding, and Figures 4 and 5 are types of Fe-Mn and Fe-Si. It is a graph showing the change in the amount of spatter generated depending on the blending amount.

Claims (1)

[Claims] 1. A low hydrogen-based coated arc welding rod in which a flux component consisting of a slag forming agent, a gas generating agent, etc. is applied to a mild steel core wire together with a fixing agent, wherein the flux is SiO ₂ :1 to 25%. (weight%, same below),
Contains _TiO2 : 0.5-20%, carbonate: 12-60%, metal fluoride: 1-25% as essential components, and further contains atomized Fe-Mn: 1-13%, atomized Fe-
A low hydrogen-based coated arc containing one or two types of Si: 3 to 23%, and in which 55% or more of the total atomized powder is composed of fine particles that have passed through 60 meshes. Welding rods. 2. A low-hydrogen coated arc welding rod according to claim 1, wherein 40% or more of the total atomized powder is composed of fine particles that pass through 60 meshes but do not pass through 200 meshes. 3. The low hydrogen-based coated arc welding rod according to claim 1 or 2, wherein the flux contains 45% or less of iron powder.