JP2007136548A - Flux cored wire for gas shielded arc welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide flux cored wire for gas shielded arc welding, a wire that makes welding highly efficiently executed in a flat position and a horizontal fillet position, through improvement of welding efficiency by solving the problems of excessive penetration of a lower bead and undercut of an upper bead, in the welding that requires a long leg ≥10.5 mm and a thick throat ≥7.5 mm. <P>SOLUTION: The flux cored wire for which flux is filled in a sheath made of soft steel or alloy steel for gas shielded arc welding is characterized in that it contains, based on the total weight of the wire, 2.00-6.00% TiO<SB>2</SB>(in terms of wt.% hereinafter), 0.20-1.50% Al<SB>2</SB>O<SB>3</SB>, 0.50-2.00% MgO, 1.50-3.50% SiO<SB>2</SB>, 0.30-2.00% ZrO<SB>2</SB>, 2.00-4.50% MnO, 0.03-0.25% K<SB>2</SB>O and 0.05-0.30% F, the balance being Fe and other components. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a flux-cored wire for gas shielded arc welding, and more particularly, can be applied to welding in steel frames, bridges, and shipbuilding industries mainly using mild steel and high-strength steel, and particularly, downward welding and horizontal cornering. The present invention relates to a flux-cored wire for gas shielded arc welding, suitable for welding with a leg length of 10.5 mm or more and a throat thickness (theoretical throat thickness) of 7.5 mm or more by welding exclusively for meat.

  In the modern industrial society, with the increase in production of large iron structures, there is an increasing demand for higher efficiency in welding construction, which requires a longer leg length and throat thickness when welding. In order to meet these requirements, especially in downward welding and horizontal fillet welding, robotic welding and semi-automation will be introduced in welding equipment, and welding materials require large leg length and large throat thickness. It was necessary to develop a flux-cored wire. Welding materials dedicated to downward and horizontal fillet welding have been developed and used, but in order to satisfy the requirements of large structures, technological development of welding materials that can produce large throat beads as well as large leg lengths is required. It became an essential environment.

  On the other hand, in conventional welding materials, welding materials satisfying large leg length beads of 8 mm or more have been developed and used in the field during downward welding and horizontal fillet welding, but leg lengths of 10.5 mm or more and 7.5 mm or more are used. Structures that require throat thickness are vulnerable to fatigue strength due to the sag phenomenon of the lower bead and the undercut of the upper bead, and two or more passes (Pass) or three passes to compensate for this fatigue strength vulnerability. (Pass) Welding phenomenon and undercut were solved by welding, but there was a problem that work efficiency decreased.

In order to solve the above problems, the present invention solves the lower bead droop and the upper bead undercut in welding that requires a leg length of 10.5 mm or more and a throat thickness of 7.5 mm or more. Thus, it is an object of the present invention to provide a flux-cored wire for gas shielded arc welding that enables welding to be performed with high efficiency in the downward and horizontal fillet postures by improving the welding efficiency.
Another object of the present invention is to provide a flux-cored wire for gas shielded arc welding in which molten metal sag and undercut failure of the upper base metal do not occur even in high current welding.

An object of the present invention is to provide a flux-cored wire for gas shielded arc welding in which an outer skin made of mild steel or alloy steel is filled with flux. TiO ₂ (converted value): 2.00 to 6.00% by weight, Al _{2 with} respect to the total weight of the wire O ₃ (converted value): 0.20 to 1.50 wt%, MgO (converted value): 0.50 to 2.00 wt%, SiO ₂ (converted value): 1.50 to 3.50 wt%, ZrO ₂ (converted value): 0.30 to 2.00 wt% , MnO (converted value): 2.00 to 4.50% by weight, K ₂ O (converted value): 0.03 to 0.25% by weight, F (converted value): 0.05 to 0.30% by weight, the balance being composed of Fe and other components This is accomplished by providing a flux-cored wire for gas shielded arc welding. Here, each said oxide component represents the value which put together the said element component contained in the wire, and the oxide component of the said element in conversion into said each oxide.

  According to the present invention, it is possible to perform the welding work with high efficiency by the downward and horizontal fillet posture, and even if welding is performed under a high current, the bead shape is poor, such as drooping of the molten metal bead and undercut of the upper bead. The problem is solved and a large leg length and a large throat thickness are obtained.

In the following, preferred embodiments of the present invention will be described in detail.
To adjust the flow rate of the molten metal and the freezing point, solidification rate and viscosity of the slag, the formation of slag during solidification of the molten metal, the solidification rate of the low melting point oxide and slag related to the solidification point and bead shape of the slag, the slag viscosity and The results of studying two aspects of the high melting point oxide that adjusts the bead shape are as follows.
First, components relating to slag formation, slag freezing point, and bead shape include Ti and Ti oxide, Al and Al oxide, Si and Si oxide, and the like.
The above Ti, Al, Si, etc. represents a deoxidizing effect during the welding, Ti oxide, Al oxide, such as Si oxide is added as slag forming agent, eventually TiO _2, Al ₂ O _3, An oxide such as SiO ₂ is formed. These oxides such as TiO ₂ , Al ₂ O ₃ , and SiO ₂ are low melting point oxides, and are involved in slag formation, slag solidification point, and bead shape during solidification of the molten metal.
Second, examples of components that adjust the solidification rate, slag viscosity, and bead shape of slag include Mg and Mg oxide, Zr and Zr oxide, and the like.
The above Mg, Zr, etc. show deoxidizing action during welding, and Mg oxide, Zr oxide, etc. are added as slag forming agents, and finally oxides such as MgO, ZrO ₂ are formed. These MgO and ZrO ₂ oxides are high melting point oxides and act as main factors for adjusting the solidification rate, slag viscosity and bead shape of slag.

Therefore, in the present invention, a high melting point oxide such as MgO or ZrO ₂ is used to adjust the solidification rate, viscosity, and bead shape of the slag so that the undercut of the upper bead and the lower bead do not occur, By using low melting point oxides such as TiO ₂ , Al ₂ O ₃ , SiO ₂ and adjusting the formation of the main slag, the solidification point of the slag, and the bead shape, the undercut of the upper bead and the lower bead do not occur Can be.
As described above, the low melting point oxide related to the formation of slag, the freezing point of the slag and the bead shape or only the high melting point oxide for adjusting the solidification rate of the slag, the slag viscosity and the bead shape, Only when these two factors are combined together as appropriate, it is not possible to obtain a large leg length and large throat thickness weld metal without undercut of the upper bead and lower bead at the high current, which is a problem. The object of the present invention can be achieved.

In addition, by adjusting the arc stabilizer such as K ₂ O and F and the component capable of adjusting the arc mounting force, the occurrence of undercut in the upper bead can be adjusted. In particular, arc stability can be ensured, the amount of spatter generated is small, and welding workability can be improved.
As described above, according to the present invention, the composition ratio of the high melting point oxides MgO, ZrO ₂ and the low melting point oxides TiO ₂ , Al ₂ O ₃ , SiO ₂ can prevent the slag from flowing down while preventing the beads from dripping. Therefore, by adjusting the value of the following formula (1) representing the relationship between the low melting point oxide and the high melting point oxide to be within the range of 1.80 to 6.50, the present invention can be achieved. Complete.
1.80 ≦ (TiO ₂ + Al ₂ O ₃ + SiO ₂ ) / (MgO + ZrO ₂ ) ≦ 6.50 (1)
Hereinafter, the role and appropriate content of each component in the present invention will be described.

TiO ₂ : 2.00 to 6.00% by weight
TiO ₂ generally acts as a slag former and arc stabilizer. When TiO ₂ is less than 2.00% by weight, the slag encapsulation is insufficient, and the appearance shape and arc stability of the bead are poor. On the other hand, if it exceeds 6.00% by weight, the content of slag increases and causes weld defects, and the content of low melting point slag also increases, which may cause drooping of beads. Accordingly, the content of TiO ₂ is preferably in the range of 2.00 to 6.00% by weight.
On the other hand, raw materials for supplying TiO ₂ include, but are not limited to, rutile (Rutile, TiO ₂ ) and ilmenite (Ilmenite, FeTiO ₃ ).

Al ₂ O ₃ : 0.20 to 1.50% by weight
Al ₂ O ₃ acts to reduce slag encapsulation, peelability, and spatter generation. If the amount is less than 0.20% by weight, the amount of spatter generated is large and the effect is not obtained. Therefore, the content of Al ₂ O ₃ is preferably in the range of 0.20 to 1.50% by weight.
On the other hand, the raw material for supplying Al ₂ O ₃ is not limited to this, and examples thereof include aluminum oxide (Aluminum oxide, Al ₂ O ₃ ).

MgO: 0.50 to 2.00% by weight
MgO is a high melting point oxide that affects the solidification rate and viscosity of the slag, affects the undercut and bead sag, and adjusts the bead shape. If MgO is less than 0.50% by weight, the bead shape hangs down and overlaps. If it exceeds 2.00% by weight, the slag viscosity increases and the slag peelability is inferior, the upper leg length is undercut, and the bead shape is poor. Become. Therefore, the MgO content is preferably in the range of 0.50 to 2.00% by weight.
On the other hand, the raw material for supplying MgO includes, but is not limited to, magnesia clinker (MgO), magnesite (Magnesite, MgCO ₃ ) and the like.

SiO ₂ : 1.50 to 3.50% by weight
SiO ₂ is a slag forming agent and an arc stabilizer, and is a component having a low freezing point and low viscosity, and having an effect for adjusting the bead shape. If SiO ₂ is less than 1.50% by weight, the arc is unstable, the amount of spatter generated increases, the slag encapsulation is not uniform, and the bead shape is poor. When it exceeds 3.50% by weight, there are many low melting point slags, and overlap occurs in the lower leg length. Therefore, the content of SiO ₂ is preferably in the range of 1.50 to 3.50% by weight.
On the other hand, the supply source of SiO ₂ is not limited to this, but includes quartzite (Quartz, SiO ₂ ), diatomaceous earth (SiO ₂ -Al ₂ O ₃ -Fe ₂ O ₃ ), positive And feldspar (Orthoclase, K ₂ O—Al ₂ O ₃ -6SiO ₂ ).

ZrO ₂ : 0.30 to 2.00% by weight
ZrO ₂ is a component that affects the solidification rate and slag viscosity of slag, influences the undercut and bead sag, and adjusts the bead shape like MgO. If ZrO ₂ is less than 0.30% by weight, there is no effect of improving the bead shape. If it exceeds 2.00% by weight, the slag viscosity becomes high and the slag peelability is poor, the undercut of the upper leg length occurs, and the bead shape is poor. Therefore, the content of ZrO ₂ is preferably in the range of 0.30 to 2.00% by weight.
On the other hand, raw materials for supplying ZrO ₂ include, but are not limited to, zircon sand (Zircon-Sand, ZrSiO ₄ ) and zirconia (Zirconia, ZrO ₂ ).

MnO: 2.00 to 4.50% by weight
MnO acts as a deoxidizer and improves the tensile strength and toughness of the weld metal. If MnO is less than 2.00% by weight, deoxidation is insufficient, so that weld defects such as blow holes are likely to occur in the welded part, and the tensile strength and toughness are poor. When MnO exceeds 4.50% by weight, the tensile strength of the weld metal is greatly increased, so that high temperature cracks are likely to occur. Accordingly, the MnO content is preferably in the range of 2.00 to 4.50% by weight.
On the other hand, the raw material for supplying MnO is not limited to this, but includes metal manganese powder (Metal Manganese Powder), ferromanganese (Ferro-Manganese), or Fe-Si-Mn.

K ₂ O: 0.03 to 0.25% by weight
K ₂ O is a component that affects the arc stabilizer and the arc mounting force. If K ₂ O is less than 0.03% by weight, the arc is unstable and the amount of spatter generated is large. If it exceeds 0.25% by weight, the arc mounting force is strong, undercutting of the upper bead occurs, and the amount of spatter generated increases. Therefore, the content of K ₂ O is preferably in the range of 0.03 to 0.25% by weight.
On the other hand, the supply source for supplying K ₂ O is not limited to this, but anorthite (Orthoclase, K ₂ O-Al ₂ O ₃ -6SiO ₂ ), potassium titanate (Potassium titanate, K ₂ TiO) ₃ ).

F: 0.05 to 0.30% by weight
F is an alkaline fluoride that acts to reduce arc stability and spatter generation and improve welding workability. If the amount of fluoride is less than 0.05% by weight, the arc is unstable and spatter is often generated, and if it exceeds 0.30% by weight, the arc concentration is relatively large and induces undercut of the upper bead, resulting in spattering. Cause excessive occurrence. Therefore, the F content is preferably in the range of 0.05 to 0.30% by weight.
On the other hand, the supply source for supplying F includes, but is not limited to, NaF, CaF ₂ , MgF ₂ , BaF ₃ , AlF ₃ , KF, and LiF.

Among the above components, when the high melting point oxide increases, the solidification rate and viscosity of the slag increase and the molten metal does not flow down. On the other hand, undercut of the upper bead occurs, and when the low melting point oxide increases, the solidification of the slag Of the above components that can control the solidification rate, slag viscosity, and bead shape of slag, taking into account the fact that the speed becomes relatively slow and causes bead sagging to induce overlap, among the above components MgO, ZrO of high melting point oxide ₂ and the low melting point oxides TiO ₂ , Al ₂ O ₃ and SiO ₂ were derived and represented by the following formula (1), and the value was controlled within the range of 1.80 to 6.50.
1.80 ≦ (TiO ₂ + Al ₂ O ₃ + SiO ₂ ) / (MgO + ZrO ₂ ) ≦ 6.50 (1)
If the value of the formula (1) is less than 1.80, an undercut of the upper bead occurs, and if it exceeds 6.50, the bead shape does not become an equal leg length and an overlap occurs due to a bead drooping phenomenon. Therefore, it is most appropriate that the value of the formula (1) is in the range of 1.80 to 6.50.

On the other hand, alloy elements such as Si and Mn can be added by a skin or a flux. Also, other alloy components (Cr, Cu, Ni, Ti, Mo, V, Nb, etc.) other than the above should be added to improve the corrosion resistance, high temperature strength, impact resistance, and high temperature corrosion resistance of welds. You can also.
Moreover, there is no restriction | limiting in the filling state of the flux by the state of a wire surface, and a cross section. There is no restriction on the surface treatment, because the surface of the wire may have good electrical conductivity and may be plated with Cu or an oxide film to prevent rusting. Moreover, although it is better to make the cross section of a wire circular, it is not limited to this.
Hereinafter, the present invention will be described in more detail based on the following examples. However, the present invention is not limited to this.

Example 1: Manufacture of wire for gas shielded arc welding Flux is filled in the outer shell of cold rolled steel (KS D 3512) so that the flux content is 12 to 18% by weight with respect to the total weight of the wire. Thus, a flux-cored wire having a wire diameter of 1.6 mm was manufactured. The components of the wire are shown in Table 1 below.
The flux-cored wire thus manufactured is welded within the range of welding conditions shown in Table 2 below and FIG. 1, and the leg length, throat thickness, bead overlap, undercut, arc stability, slag peelability, slag The encapsulating property and the amount of spatter generated were evaluated. The results are summarized in Table 3 below.

As can be seen from Tables 1 and 3 above, in Comparative Example 17, an overlap occurred outside the upper limit of TiO ₂ , and the amount of spatter generated was also large. In Comparative Example 18, the bead overlap occurred due to the slag flowing off from the upper limit of SiO ₂ , and the slag peelability was poor.
As in Comparative Example 17, Comparative Example 19 deviated from the upper limit value of TiO ₂ and generated an overlap, resulting in a large amount of spatter. Comparative Example 20 is not only deviated from the upper limit value of MgO but also deviated from the lower limit value of F, an undercut of the upper leg length occurred, the weld bead shape was poor, and arcing in slag peelability and welding workability Stability was poor.
In Comparative Example 21, the value of the formula (1) deviates from the appropriate upper limit value, so that there are many low melting point oxides and few high melting point oxides, overlap occurs in the bead shape, and the slag peelability is low. It was bad. Comparative Example 22 deviated from the lower limit of SiO ₂ , resulting in poor arc stability, and a large amount of spatter was generated.
Comparative Example 23 deviates from the lower limit value of F, and equation (1) also deviates from the appropriate lower limit value. The arc stability is poor, the amount of high melting point oxide is low, the amount of low melting point oxide is small, and the upper leg length is low. Undercut occurred and slag peelability was poor. In Comparative Example 24, the upper leg length undercut occurred due to the deviation from the lower limit value of TiO _{2 and} the upper limit value of Al ₂ O ₃ , and the slag peelability was poor. Moreover, the overall slag forming agent was insufficient, and the slag encapsulation was also poor.
Comparative Example 25 deviated from the lower limit value of Al ₂ O ₃ and generated a large amount of spatter in welding workability. Comparative Example 26 deviated from the lower limit value of ZrO ₂ , undercut occurred in the upper leg length, and the weld bead was poor. In Comparative Example 27, both MnO and K ₂ O are out of the lower limit values, the arc stability in welding workability is poor, the amount of spatter is large, the tensile strength decreases due to the effect of MnO, and the toughness is the standard value Did not meet.
Comparative Example 28 deviated from the upper limit value of K ₂ O and generated a large amount of spatter in welding workability. In Comparative Example 29, both MnO and ZrO ₂ deviated from the upper limit values, and the bead shape was poor due to the occurrence of an undercut in the upper leg length.
In Comparative Example 30, the bead overlap occurred due to the deviation from the upper limit value of MnO and the lower limit value of MgO, and the bead shape was poor. In Comparative Example 31, both ZrO ₂ and F deviated from the upper limit, undercut occurred in the upper leg length, slag peelability was poor, and the amount of spatter generated was large in welding workability.
On the other hand, both Examples 1 to 16 of the present invention were not only free from molten metal and slag dripping, but also excellent in slag peelability, with a bead shape with a leg length of 10.5 mm or more and a throat thickness of 7.5. It was confirmed that the arc stability and the amount of spatter were small and welding workability was good.

The figure which showed schematically the fillet-welding conditions with respect to structures mainly used in the Example and comparative example of this invention, such as a steel frame, a bridge, and the shipbuilding industry. FIG. 2 is a longitudinal cross-sectional view of a fillet weld for indicating a bead name during fillet welding in FIG. FIG. 2 is a longitudinal sectional view of an undercut defect that is a kind of main defect during fillet welding in FIG. FIG. 2 is a longitudinal sectional view of an overlap defect which is a kind of main defect during fillet welding in FIG.

Claims (2)

In the flux-cored wire for gas shield arc welding that fills the outer shell made of mild steel or alloy steel with flux,
TiO ₂ (converted value): 2.00 to 6.00 wt%, Al ₂ O ₃ (converted value): 0.20 to 1.50 wt%, MgO (converted value): 0.50 to 2.00 wt%, SiO ₂ (based on the total weight of the wire (Converted value): 1.50 to 3.50% by weight, ZrO ₂ (converted value): 0.30 to 2.00% by weight, MnO (converted value): 2.00 to 4.50% by weight, K ₂ O (converted value): 0.03 to 0.25% by weight, F (Conversion value): A flux-cored wire for gas shielded arc welding characterized by including 0.05 to 0.30% by weight and the balance being composed of Fe and other components. _{2. The} flux-cored wire for gas shielded arc welding according to claim 1, wherein the contents of TiO ₂ , Al ₂ O ₃ , SiO ₂ , MgO, and ZrO ₂ satisfy the following formula (1).
1.80 ≦ (TiO ₂ + Al ₂ O ₃ + SiO ₂ ) / (MgO + ZrO ₂ ) ≦ 6.50 (1)