JPH0520200B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a composite wire for gas-shielded arc welding used for welding steel structures, and more specifically, a composite wire with a small leg length that has a stable arc at low current and a good bead shape. This invention relates to a composite wire for gas-shielded arc welding that provides fillet weld metal. [Conventional technology] Composite wire for gas-shielded arc welding (hereinafter referred to as composite wire) filled with TiO ₂ -based flux has TiO ₂ as its main component, so the arc is more stable than solid wire even during CO ₂ shield welding. It enables welding with fewer spatters, and has the advantage of a beautiful appearance because the bead is completely covered by the generated slag, so it has been widely used for butt welding and fillet welding of steel materials. Furthermore, in recent years, welded structures have become diverse, and in the shipbuilding industry in particular, fillet beads with a good bead shape and leg length of 3 to 4 mm can be obtained even with semi-automatic welding for steel plates with a thickness of about 3.2 mm to 6 mm for passenger ships. Demand for the development of composite wires has been increasing. However, it has been difficult to meet this demand with conventional composite wires. In other words, 3 conventional composite wires are semi-automatically welded.
To obtain a bead with a small leg length of ~4 mm, it is necessary to weld at a low current. However, when welding with a low current, for example with a composite wire of 1.2 mmφ, the arc is unstable and the bead tends to become irregular at 170 A or less.
There were problems such as undercutting. Another method is to reduce the wire diameter to 0.9mmφ or 1.0mmφ and weld by increasing the current density at a low current, but the stability of the arc is not improved much, and fillet beads with small legs are produced by semi-automatic welding. The reality was that it was not possible to achieve this goal. [Problems to be Solved by the Invention] The present invention has been made with attention to these circumstances, and it is possible to provide fillet weld metal with a small leg length and a stable arc at low current and a good bead shape. The object of the present invention is to provide a composite wire for gas-shielded arc welding. [Means for Solving the Problems] The composite wire of the present invention, which has achieved the above object, contains TiO ₂ :5.6 as a slag forming agent based on the total weight of the wire.
~8.5wt%, _ZrO2 :0.4 _~ 2.5wt% _{, KMg2.5Si4O10}
Contains F ₂ (potash tetrasilicon mica): 0.2 to 1.2 wt%, Si: 0.3 to 0.8 wt%, Mn: 1.0 to 3.0 wt% as deoxidizing agents, total amount of deoxidizing agents other than Si and Mn: 0.2 The gist is that the flux is limited to 10 to 25 wt% of the total weight of the wire, and fluxes consisting of slag forming agents, alloying agents, iron powder, and unavoidable impurities are limited to 10 to 25 wt% based on the total weight of the wire. That is, the present invention takes advantage of the characteristics of TiO ₂ composite wire, which has good welding workability and welding efficiency, and improves the wire composition of TiO ₂ composite wire in order to improve arc stability in the low current range. It was completed as a result of various studies, and the flux composition shown in the above structure, especially the amount of TiO ₂ as a slag forming agent, the amount of ZrO ₂ , KMg _2.5 Si ₄ O ₁₀ F ₂ amount, and the amount of Si as a deoxidizing agent. By appropriately setting the amount of , Mn, and the total amount of deoxidizers other than Si and Mn, the arc is stabilized, especially in the low current range, and this improves droplet migration and improves the bead shape. We succeeded in obtaining a fillet bead with a good small leg length. [Function] That is, the present inventor discovered that TiO ₂ , ZrO ₂ , KMg _2.5 Si ₄
In order to investigate the appropriate content of O ₁₀ F ₂ , Si, Mn, and deoxidizers other than Si and Mn, we used wire compositions of 1.2 mmφ and flux filling rate of 15.0 based on the wire components shown in Tables 1 to 6. We prototyped a composite wire of wt% and used horizontal fillet welding to achieve a target leg length of 3.0 to 4.0 mm under the following welding conditions, and evaluated the arc condition and bead shape using semi-automatic welding. Welding conditions Polarity DCRP Welding current 150A Wire protrusion length 10~15mm Gas CO ₂ 25/min Steel plate SM41B (6t)

【table】

【table】

【table】

【table】

【table】

[Table] Figure 1 shows the appropriate content of TiO ₂ ,
If TiO ₂ is less than 5.6 wt%, both the arc condition and the bead shape are poor, and if it is 5.6 wt% or more, the arc becomes stable and the bead shape becomes good. However, 8.5wt
If the content exceeds 5%, the slag will get caught in the weld bead, resulting in poor bead shape. That is, it was found that the appropriate range of TiO ₂ is 5.6 to 8.5 wt%. Figure 2 is a diagram showing the appropriate content of ZrO ₂ ,
When ZrO ₂ is 0.4wt%, both the arc condition and the bead shape are poor, and when it exceeds 2.5wt%, the weld bead becomes irregular. In other words, the appropriate range of ZrO ₂ is 0.4-2.5wt%
It turned out to be. FIG. 3 is a diagram showing the appropriate content of KMg _2.5 Si ₄ O ₁₀ F ₂ . Regarding the bead shape, if it is less than 0.2wt%, the bead will be uneven and the surface will be uneven;
If it exceeds %, it will be difficult to weld and the bead will become irregular.
Furthermore, in an arc state, if it exceeds 1.2 wt%, the arc becomes unstable and spatter increases. In other words, the range where the bead shape and arc condition are good is:
It was found to be 0.2-1.2wt%. FIG. 4 is a diagram showing the appropriate content of Si. In an arc state, if it exceeds 0.8 wt%, the droplets become large agglomerates, the arc becomes unstable, and the bead shape becomes poor. In addition, in the bead shape, 0.3wt%
If it is less than that, there will be insufficient deoxidation and pits and blowholes will occur in the bead. In other words, the appropriate range for Si is 0.3~
It was found to be 0.8wt%. FIG. 5 is a diagram showing the appropriate content of Mn,
In the arc state, if it exceeds 3.0wt%, like Si,
The droplets become large clumps, the arc becomes unstable, and the bead shape becomes poor. In addition, regarding the bead shape,
If it is less than 1.0wt%, deoxidation will be insufficient and the bead will become pitted.
A blowhole occurs. That is, it was found that the appropriate range of Mn is 1.0 to 3.0 wt%. Figure 6 is a diagram showing the appropriate content of deoxidizing agents other than Si and Mn, and the total amount of deoxidizing agents other than Si and Mn is
If it exceeds 0.2wt%, the droplets will become large clumps, the arc will become unstable, and the bead shape will also be poor. That is,
It was found that the total amount of deoxidizers other than Si and Mn was less than 0.2wt%. Below, we will discuss the basis for limiting ingredients based on the above findings.・ TiO ₂ in the slag forming agent: 5.6 to 8.5 wt% The droplets formed at the tip of the wire tend to become coarser on the one hand due to surface tension, and on the other hand due to the influence of the pinch force caused by the welding current. It is about to be ejected from the tip of the wire. Therefore, if the welding current is too low, the pinching force is insufficient and the force for ejecting the wire from the tip is weak, so the droplet grows rapidly due to surface tension, becomes a large clump, and then falls due to gravity (globulular). transition). Therefore, if the droplets form into large clumps, arc generation will be uneven and the arc will not be stable. In order to improve this, it is necessary to increase the oxygen concentration of the droplets.
The goal is to reduce the surface tension of the droplets and make the droplets finer. TiO ₂ is 5.6 to 8.5wt to achieve the above effect.
It is necessary to contain %. TiO ₂ is an acidic oxide and is effective in increasing the oxygen concentration of droplets and making them finer. If it is less than 5.6 wt%, it has no effect on arc stability at low currents, and if it exceeds 8.5 wt%, the viscosity of the slag increases, making the weld bead uneven and making the bead surface uneven, which is not preferable. - Among the slag forming agents, ZrO ₂ : 0.4 to 2.5 wt% ZrO ₂ is an acidic oxide like TiO ₂ and is effective in increasing the oxygen concentration of the droplets and making the droplets finer.
In order to exhibit this effect, the content must be 0.4 wt% or more. However, since ZrO ₂ has a high solidification temperature, if it exceeds 2.5 wt%, the weld bead will become irregular, similar to TiO ₂ , which is not preferable.・KMg _2.5 Si ₄ O ₁₀ F ₂ among slag forming agents
:0.2~1.2wt% Addition of TiO ₂ and ZrO ₂ can increase the oxygen concentration of the droplets and make the droplets finer, improving the stability of the arc, but the viscosity of the produced slag is low and fillet The weld bead is irregular and the bead surface tends to become uneven. Furthermore, as a result of various studies to improve the weld bead, we developed a product proposed in JP-A-54-127848 for the purpose of improving the fatigue strength of the weld bead toe of a low-hydrogen coated arc welding rod. was done,
By containing 0.2 to 1.2 wt% of KMg _2.5 Si ₄ O ₁₀ F ₂ in the composite wire, it was possible to adjust the viscosity of the slag, improve the alignment of the weld bead, and make the bead surface smooth. In addition, K ⁺ ions contained in KMg _2.5 Si ₄ O ₁₀ F ₂ decompose in the arc and have the effect of stabilizing the arc, thereby improving arc stability at low currents. In order to exhibit these effects, it must be contained at 0.2 wt% or more. If it exceeds 1.2wt%, the viscosity of the slag becomes too high, making it difficult to weld and making it difficult to form beads. Furthermore, since a large amount of K ⁺ ions are included, the arc length becomes long, which is undesirable because it causes an increase in the amount of spatter and fumes.・Si: 0.3 to 0.8wt% At low currents, the pinch force is insufficient and the force to separate from the wire tip is weak, so the droplet stays at the wire tip for a long time and the reaction time with the deoxidizing agent increases. . Particularly in a situation where an excessive amount of deoxidizer exists, the oxygen concentration of the droplet decreases, the surface tension of the droplet increases, and the droplet becomes a large agglomerate. Furthermore, an oxide layer formed by reaction with the deoxidizing agent is formed on the surface of the droplet and disturbs the arc generation point. In order to prevent these adverse effects, it is necessary to suppress the increase in the surface tension of the droplets and the formation of a surface oxidation layer due to the deoxidizing agent. However, an amount is necessary to maintain good performance of the weld metal. In order to satisfy these requirements, the amount of Si needs to be 0.3 to 0.8 wt%. If it is less than 0.3wt%, deoxidation will be insufficient and a good weld metal cannot be obtained. On the other hand, 0.8wt%
If it exceeds this, the surface tension of the droplet will increase and the droplet will become a large agglomerate, and an oxide layer will be formed on the surface of the droplet, disturbing the arc. - Mn: 1.0 to 3.0 wt% Like Si, by containing Mn within an appropriate range, it is possible to suppress an increase in the surface tension of droplets and the formation of a surface oxide layer. However, 1.0wt
If it is less than %, deoxidation will be insufficient and the impact performance of the weld metal will deteriorate. On the other hand, if it exceeds 3.0 wt%, the surface tension of the droplet will increase, similar to Si, and the droplet will become large agglomerates, and an oxide layer will be formed on the surface of the droplet, disturbing the arc.・Total amount of deoxidizers other than Si and Mn: 0.2wt% or less In order to suppress the oxide layer formed on the droplet surface, as mentioned above, the amount of Si and Mn should be contained within the appropriate range. In addition, it is necessary to appropriately limit the total amount of deoxidizers other than Si and Mn. That is,
C, A, Mg, Ti,
One or more types of Zr, Ca, etc. are contained, but if the total amount exceeds 0.2 wt%, the oxygen concentration of the droplets is reduced, the droplets become large agglomerates, and the arc becomes unstable. In addition, Si and Mn tend to form an oxide layer on the surface of the droplet, making the arc unstable.
The total amount of deoxidizers other than Mn must be 0.2wt% or less. As mentioned above, TiO ₂ , ZrO ₂ , KMg _2.5 Si ₄ O ₁₀ F ₂ , Si
By specifying the amount of Mn, the amount of Mn, and the total amount of deoxidizing agents other than Si and Mn, it is possible to obtain a composite wire that provides a fillet weld metal with a stable arc at low current and a good bead shape and a short leg length. I can do it. The basic structure of the present invention is as described above, but other slag forming agents include SiO ₂ , A ₂ O ₃ ,
FeO, Fe ₂ O ₃ , MgO, Na ₂ O, K ₂ O are exemplified,
By containing one or more of these, the bead can be uniformly covered with slag and the bead shape can be improved. In addition, as an alloying agent, by containing one or more alloying elements such as Ni, Cr, V, and Nb,
It can provide high toughness and weather resistance to weld metal. Furthermore, by containing Bi, the slag removability can be improved, and by further containing iron powder, the welding speed can be improved. Furthermore, the filling rate is not allowed without limit;
It should be in the range of 10 to 25 wt% based on the total weight of the wire.
If the filling rate is less than 10wt%, the arc will be unstable and the slag encapsulation will deteriorate, resulting in a convex bead with many undercuts.On the other hand, if it exceeds 25wt%, the amount of slag produced will be excessive, resulting in slag entrainment. This is likely to occur, and there is a risk of wire breakage occurring during wire drawing. [Example] Table 7 shows the configuration of the prototype composite wire, and Table 8 shows the test results. In Table 7, the wire
No. 1 to No. 17 are comparative examples, and No. 18 to No. 30 are examples of the present invention. All composite wires use a mild steel outer sheath, are filled with flux and the pipe while vibrating using the technology described in Japanese Patent Publication No. 45-30937, and are annealed at 650°C during the wire drawing stage. The surface is Cu plated and finished to a diameter of 1.2mmφ. The test was conducted using the method described in the explanation of [Function], and the arc condition and bead shape were evaluated.
As a result, No. 1 had a small amount of TiO ₂ and had a poor arc condition and bead shape, while No. 2 had a large amount of TiO ₂ and had a good arc condition, but the slag was caught in the bead and a good weld bead was not obtained. I couldn't get it. No.3 is
The amount of ZrO ₂ was small, the arc condition was poor, and the bead shape was also poor. In No. 4, the amount of ZrO ₂ was large and the arc condition was good, but the slag was caught in the bead and was poor. In No. 5, since the amount of KMg _2.5 Si ₄ O ₁₀ F ₂ was small, the bead was irregular and the surface was uneven, and a good weld bead could not be obtained. No. 6 had a large amount of KMg _2.5 Si ₄ O ₁₀ F ₂ and was poor in arc condition and bead shape.
No. 7 had a small amount of Si, and No. 9 had a small amount of Mn, so pits and blowholes occurred. No. 8 has a Si amount, and No.
Sample No. 10 contained a large amount of Mn, so both the arc condition and bead shape were poor. In No. 11 to No. 15, the total amount of deoxidizer other than Si and Mn was outside the range of the present invention, and both the arc condition and bead shape were poor. No. 16 had a low flux filling rate, resulting in poor arc conditions and bead shape. No.17 has a high flux filling rate,
The amount of slag produced was excessive, and slag entrainment occurred. On the other hand, No. 18 to No. 30 have TiO ₂ amount, ZrO ₂ amount,
Since the amount of KMg _2.5 Si ₄ O ₁₀ F ₂ , the amount of Si, the amount of Mn, and the total amount of deoxidizing agents other than Si and Mn are within the scope of the present invention,
Even at low currents, the arc was stable and a good weld bead could be obtained.

【table】

[Table] *Comparative examples

【table】

【table】

【table】

[Table] [Effects of the Invention] As described above, according to the present invention, it is possible to obtain a fillet weld metal with a small leg length and a stable arc at low current and a good bead shape.

[Brief explanation of drawings]

Figure 1 shows the relationship between the amount of TiO ₂ and the arc state and bead shape. Figure 2 shows the relationship between the amount of ZrO ₂ and the arc state and bead shape. Figure 3 shows the relationship between the amount of ZrO 2 and the arc state and bead shape.
KMg _2.5 Si ₄ O ₁₀ F Figure 4 shows the relationship between the amount of Si 4 O 10 F ₂ and the arc state and bead shape. Figure 4 shows the relationship between the amount of Si and the arc state and bead shape. Figure 5 shows the relationship between the amount of Mn and the arc state. and a diagram showing the relationship between bead shapes,
FIG. 6 is a diagram showing the relationship between the total amount of deoxidizing agents other than Si and Mn, the arc state, and the bead shape.

Claims (1)

[Claims] 1 As a slag forming agent based on the total weight of the wire
_TiO2 : 5.6-8.5wt%, _ZrO2 : 0.4-2.5wt%,
KMg _2.5 Si ₄ O ₁₀ F ₂ (potassium tetrasilicon mica): 0.2~1.2wt
%, Si as deoxidizer: 0.3~0.8wt%, Mn: 1.0~
Total amount of deoxidizing agent other than Si and Mn, including 3.0wt%:
Limited to 0.2wt% or less, other slag forming agents,
A composite wire for gas-shielded arc welding, characterized in that it is filled with flux consisting of an alloying agent, iron powder, and unavoidable impurities in an amount of 10 to 25 wt% based on the total weight of the wire.