JPH0331555B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a composite wire for arc welding that can increase the melting rate of the wire and reduce spatter loss during welding in order to improve welding efficiency. Composite wire for arc welding has characteristics that depend on the type of flux it contains, but in general, the arc is more stable, there are fewer spatters, and welding workability is better than solid wire, regardless of whether a shielding gas is used or not. Furthermore, since slag with appropriate viscosity and melting point is produced and this encapsulates the molten metal, it has many advantages such as excellent bead appearance. For this reason, its usage has been rapidly increasing in recent years. In addition, in terms of welding efficiency, when comparing the same wire diameter, the current density of composite wire containing flux is higher than that of solid wire, so the welding speed tends to be higher, which is also the reason why the amount used is increasing. This is one of the causes. However, there is a strong desire in industry to further increase the efficiency of the welding process. In response to such industrial demands, the present inventors conducted detailed studies on flux prescription, flux filling rate, outer metal material, etc. in order to develop a composite wire with a high welding speed. We found that the welding speed of composite wires can be improved by reducing the amount of arc stabilizer in the flux and increasing the flux filling rate, but it can be further improved by increasing the amount of oxygen and decreasing the amount of carbon in the wire sheath. As a result, the present invention was completed. That is, the present invention provides a composite wire in which a cavity surrounded by a steel sheath is filled with flux, in which the oxygen content is 0.01 to 0.08% by weight, the carbon content is 0.05% or less,
Si content is 0.25% or less and Mn content is 1% or less, balance
This is a composite wire for arc welding characterized by using a steel jacket made of Fe and unavoidable impurities. The composite wire according to the present invention will be explained in detail below. In the present invention, the amount of oxygen in the wire sheath is 0.01~
The reason for setting it to 0.08 is that as the amount of oxygen in the outer metal increases, the surface tension of the molten metal at the tip of the wire decreases, and the droplet detaches faster. Accelerating the detachment of the droplets shortens the time they stay at the tip of the wire, suppressing the rise in temperature of the droplets due to Joule heat and arc radiant heat, and as a result improving the thermal efficiency of the wire melting phenomenon. Therefore, the same heat generation during welding, that is, the same current and
Comparing the voltage conditions, speeding up the detachment of the droplet increases the melting rate of the wire. This fact is clear from the experimental results shown in FIG. That is,
_TiO2 30 on steel skin with oxygen content ranging from 0.003 to 0.1%
%, SiO2 ₅ %, _{Al2O3 4} %, Fe-Si (45%Si) 15%,
We prototyped a 1.2φ composite wire containing 15% flux of 25% Fe-Mn (75%Mn), the balance being iron powder, and operated it under the conditions of 300A, 30V, distance between chip and base material of 20mm, and _CO2 flow rate of 20/min. The wire welding speed per minute was determined in downward welding. As is clear from the experimental results shown in Figure 1, when the amount of oxygen in the wire jacket is small, the melting rate of the wire is 95g/
Although the amount of oxygen starts to improve from around 0.005%, a high welding rate can be obtained with almost no change at 0.01% or more. Therefore, by setting the oxygen content of the wire sheath used in the composite wire to 0.005% or more, it is possible to increase the melting rate of the wire. However, when the amount of oxygen exceeds 0.08%, the viscosity of the molten metal decreases too much, and even in downward position welding, the molten metal flows easily, making it easy to cause fusion failure. It has also been found that in order to ensure particularly good workability in position welding such as vertical welding, it is desirable to set the upper limit of the oxygen content to 0.04%. Furthermore, in the wire of the present invention, the amount of carbon in the wire sheath is reduced.
The content is kept at 0.05% or less in order to reduce spatter loss during welding. That is, as mentioned above, the wire of the present invention uses a mild steel sheath metal with a high oxygen content in order to increase the melting rate of the wire, but the wire sheath with a high oxygen content has a marked tendency to generate spatter due to the carbon content of the wire sheath. It has become clear that there is a significant impact on The same flux used in the experiment shown in Figure 1 was applied to a steel jacket with an oxygen content of around 0.03% and a carbon content of the wire jacket in the range of 0.01 to 0.10%, and was filled at 15% as shown in Figure 1, causing spatter. The amount was investigated. As a result, as shown in FIG. 2, it was found that the smaller the amount of carbon, the more the spatter was reduced. In particular, when the carbon content is 0.05% or less, the occurrence of spatter is extremely reduced. This phenomenon occurs when there is a lot of oxygen and carbon in the wire sheath, and the C+O→CO reaction occurs violently during welding, resulting in significant spatter. However, by controlling the amount of carbon, the C+O→CO reaction can be suppressed, reducing spatter loss. became possible. In this way, high oxygen
The reason for the increase in spatter loss in composite wires using a wire sheath with a high carbon content is the presence of Si in the wire sheath.
This is also due to the lack of deoxidizing elements such as Mn. If large amounts of Si and Mn are added to the wire sheath, Si
+O ₂ →SiO ₂ and Mn+O → MnO ₂ reactions occur selectively, and C+O → CO reaction is suppressed, but Si, Mn
Adding a large amount of Si impairs the formability and drawability of the wire, so keep Si at 0.25% or less and Mn at 1% or less. Therefore, in order to increase the wire melting rate and reduce sputter loss when using a wire sheath made of low Si and Mn based on wire formability and drawability, it is necessary to reduce oxygen in the wire sheath as in the present invention. It is particularly effective to control the amount of carbon to 0.01 to 0.08% and the amount of carbon to 0.05% or less. Note that the amount of carbon in the wire sheath is a factor that increases spatter when the amount of oxygen is high, as explained above, but the amount of carbon in the flux may have almost no effect depending on the method of addition. There was found.
For example, when carbonates such as CaCO ₃ and LiCO ₃ are added, CO ₂ is rapidly generated due to arc heat, which causes an increase in spatter. However, it has been found that when added to so-called deoxidizing metals or alloys, such as iron-manganese alloys, which have a stronger affinity for oxygen than carbon, they do not lead to an increase in spatter. This is thought to be because the deoxidizing element suppresses the rapid C+O→CO reaction. Therefore, as a result of using a low carbon wire sheath to avoid spatter loss, if the amount of carbon in the weld metal is insufficient and sufficient strength cannot be ensured, silicon, manganese, etc. should be added to ensure strength. is also possible. However, this method has the disadvantage of high cost, so adding carbon to the deoxidizing metal to yield the weld metal is the most inexpensive and practical solution. Furthermore, most of the carbon in graphite or lubricating oil components applied to the wire surface to improve wire feedability during welding is scattered by Joule heat or arc heat caused by the current flowing through the wire, resulting in a C+O→CO reaction. This is unlikely to cause an increase in spatter. Therefore, there are no particular restrictions on the various surface treatments that can be applied to improve wire feedability and rust resistance. In addition, the type of flux included in the wire sheath is not particularly limited, and composite wire for gas shield welding whose main component is TiO ₂ , CaF ₂ ,
Composite wires for gas shield or self-shield welding that are mainly composed of metal fluorides such as BaF ₂ , composite wires for gas shield welding that are mainly composed of metal powder with reduced slag-forming agents, etc. can be made using the wire sheath of the present invention. can be manufactured. The weight percentage of the flux contained in the wire sheath is preferably about 5 to 45%; if it is less than 5%, the amounts of the slag forming agent, alloying agent, and deoxidizing agent are insufficient, making it impossible to perform sound welding. On the other hand, if the wire is filled with more than 45% flux, the wire sheath becomes too thin, making it easy to break and deteriorating the wire feedability. Therefore, the weight ratio of the flux to the wire is preferably 5 to 45%. Further, the cross-sectional shape of the wire is not particularly specified, and the effect of the present invention can be achieved with any cross-section shown in FIG. Since there is no moisture absorption and the wire has no directionality, it has the advantage of extremely reducing the frequency of troubles occurring during welding. Furthermore, since various treatments can be freely applied to the wire surface in this cross section, it is also possible to perform copper plating for the purpose of improving electrical conductivity and rust resistance. The wire diameter can be freely selected from a small diameter of about 1.2 mmφ to a large diameter of about 4 mmφ depending on the application. Next, the present invention will be explained in more detail with reference to Examples. Example Table 1 shows the configuration and test results of the prototype wire. In the same table, Nos. 1 to 3 are comparative examples, and Nos. 4 to 8 are examples of the wires according to the present invention. Each wire had a cross-sectional shape as shown in Fig. 3A, with no openings in the wire sheath, and the surface was copper plated to a diameter of 1.2 mm. Welding efficiency is determined by the welding current using a downward automatic welding machine.
Welding was carried out under the following conditions: 300 A, arc voltage 30 V, welding speed 30 cm/min, tip-to-base metal distance 20 mm, CO ₂ flow rate 20/min, and arc time 1 minute, and the melting rate and deposition rate of the wire were actually measured. The degree of spatter loss was determined by observation during welding and the magnitude of welding efficiency. Since wires No. 1 and 2 have low oxygen and high oxygen content, welding workability is good, but the welding speed is slow. No. 3 with increased oxygen content to 0.0860%, exceeding the upper limit of the present invention
The wire has a fast melting rate of 115 g/min, but the molten metal flows easily and has a high carbon content, so there is a lot of spatter loss.

【table】

[Table] On the other hand, wires Nos. 4 to 8 according to the present invention have a high melting rate and a small spatter loss. It was also confirmed that welding workability was good. As clarified in the above examples, high oxygen
The composite wire of the present invention manufactured using a low-carbon wire sheath has a fast wire melting rate, high welding efficiency, and excellent welding workability, so it is expected to greatly contribute to improving welding efficiency in the future. It is expected.

[Brief explanation of the drawing]

Figure 1 shows the relationship between the amount of oxygen in the wire sheath and the melting rate, Figure 2 shows the relationship between the amount of carbon in the wire sheath and the amount of spatter, and Figure 3 shows an example of the cross-sectional shape of the wire. be.

Claims (1)

[Claims] 1 In a composite wire formed by filling a flux in a cavity surrounded by a steel jacket, the amount of oxygen is
0.01-0.08%, carbon content 0.05% or less, Si content 0.25%
A composite wire for arc welding, characterized by using a steel outer sheath with a Mn content of 1% or less and the balance consisting of Fe and inevitable impurities.