JPH02268996A - Flux cored wire for gas shielded arc welding - Google Patents

Abstract

PURPOSE:To decrease the amt. of the spatters to be generated and to allow a highly efficient welding with a high deposition characteristic by specifying the content of C in a steel sheath, the content of iron powder with respect to a total flux and the content of FeO in the iron powder. CONSTITUTION:The flux cored wire for gas shielded arc welding is the flux cored wire formed by filling the flux contg. 90% metal powder essentially composed of iron powder into the steel sheath at 20 to 25% by the weight of the wire. The content of the C in the steel sheath is 0.01 to 0.006%, the content of the iron powder with respect to the total flux is 41 to 87% and the content of the FeO in the iron powder is 2.3 to 12.5%.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a flux-cored wire for gas-shielded arc welding used for welding steel structures, and more specifically to a flux-cored wire that generates less spatter and has higher efficiency. The present invention relates to a metal powder-based flux-cored wire that can be welded with ease.

[Prior Art] Recently, flux-cored wires for gas-shielded arc welding have come to be widely used for welding steel structures using various steel types including 50 kg class high tensile strength mild steel. The reason for this is that flux-cored wire has good welding workability due to the action and effect of the flux filled inside it, provides a good bead appearance and shape, and has a high wire welding speed, which improves welding efficiency. It will be done.

However, with the recent trend toward automation and robotization of welding, there is a long-awaited development of flux-cored wires with even higher performance and efficiency.

This flux-cored wire has an outer sheath made of steel, and the inside thereof is filled with 10 to 30% flux.

The flux to be filled inside can be roughly divided into those consisting of slag agents such as titania, deoxidizing agents such as Si and Mn, and alloying agents, and those consisting of metal powders such as iron powder, Si and Mn. However, the present invention relates to the latter metal powder-based flux-cored wire.

Although conventional metal powder-based flux-cored wires have the following features, they have the following drawbacks and have not been put to practical use.

■ It is highly efficient as it can achieve a welding amount equal to or greater than that of solid wire.

■ Since slag generation is low and welding efficiency is high, continuous welding is possible without the need for slag removal during multi-layer welding of thick plates.

■ Since metals and alloys can be added to the filling flux, there is a wide degree of freedom in adjusting the weld metal composition.

■ It is possible to add metals, alloys, and small amounts of oxides that are difficult to add to steel.

Although the metal powder-based flux-cored wire has many features as described above, it generates more spatter than the titania-based flux-cored wire, especially during arc welding using carbon dioxide as a shielding gas, and reduces welding efficiency. Currently, metal powder-based flux-cored wires have not been widely put into practical use due to the problem of deterioration.

In order to suppress the occurrence of such spatter, for example, Japanese Patent Application Laid-Open No. 60-257993 and Japanese Patent Application Laid-Open No. 61-180896 are disclosed.
The technology described in the above publication is known. The former is aimed at reducing spatter by stabilizing the arc by adjusting the fluidity of the flux, and the latter by adjusting the flux rate and the amount of carbon or arc stabilizer added.

However, the above technology is mainly aimed at improving welding workability, and is fully satisfactory in terms of welding efficiency, which is the primary characteristic of metal powder wire, that is, high weldability. isn't it.

[Problems to be Solved by the Invention] The present invention has been made to solve the above-mentioned problems with conventional wires, and it is of course possible to reduce the occurrence of spatter even in arc welding using a carbon dioxide shield. The present invention provides a metal powder-based flux-cored wire that enables more efficient welding.

[Means for Solving the Problems] The flux-cored wire for gas-shielded arc welding of the present invention has a steel outer sheath containing flux containing 90% or more of metal powder, mainly iron powder, in an amount of 10 to 25% by weight of the wire. In the flux-cored wire formed by filling, the C of the steel outer shell is
The iron powder content is 41 to 87% with respect to the total flux, and the FeO content in the iron powder is 0.01 to 0.06%.
is 2.3 to 12.5%.

The present invention will be explained in detail below.

First, in the present invention, the metal powder content in the flux is limited to 90% or more in order to prevent excess slag from being generated during welding and to improve welding efficiency. If the ratio of metal powder in the flux is less than 90%, the welding efficiency will be lower than that of solid wire, and the amount of slag produced will be too large, requiring slag removal after each pass, resulting in a decrease in welding efficiency. Therefore, 90% or more of the flux must be metal powder. Note that the metal powder referred to here includes iron powder, S
It means deoxidizing elements such as i, Mn, Ti, B, Ai, Mg, and [:a, and alloying elements such as Ni, Cr, Mo, and Cu. These elements may be added singly or as an alloy of these elements.

Next, the iron powder content in the metal powder is 41 to 41% relative to the total flux.
The reason for setting it to 87% is to improve the welding speed of the metal powder composite wire and increase the welding efficiency. If the iron powder in the metal powder is less than 41%, no effect of improving welding efficiency is observed, and the welding efficiency is 87%.
When the
Since the absolute amounts of deoxidizing agents such as i and alloying agents such as Ni, Cr, and Mo are insufficient, desired weld metal performance cannot be obtained, and the arc becomes unstable and spatter occurs frequently.

Next, the reason for filling the flux with 10 to 25% by weight of the wire is that when the flux filling rate is low, the area ratio of the outer sheath to the cross-sectional area of the wire increases, making it easier for current to flow. No melting effect can be expected, and as a result, the melting rate decreases. Further, since the arc is too concentrated, it is difficult to expect the arc to spread, and the bead shape becomes convex, resulting in poor compatibility with the base material.

On the other hand, if the flux filling rate becomes too high, the area ratio of the outer skin becomes smaller, the current density becomes higher, and the heat generated by the outer skin resistance increases. However, the tendency of over-melting of the outer skin becomes significant and the arc becomes unstable. As a result, spatter occurs frequently, reducing wire welding speed, and welding defects such as undercuts are likely to occur. Furthermore, the wire rigidity decreases due to the thinning of the outer skin, making it easier for buckling to occur during wire feeding, which also leads to a decrease in welding performance. For the above reasons,
The flux filling rate was set at 10 to 25%.

Next, by adjusting the amount of iron powder and metal powder added within the above range, it is possible to improve welding efficiency, which is a feature of metal powder-based flux wire, but spatter, which is the biggest problem with conventional methods, can be achieved. It is not possible to reduce the amount and simultaneously achieve better weldability. As a result of repeated experiments aimed at reducing spatter and at the same time improving welding performance, the present inventors found that the components in flux-cored wire, especially the amount of C, greatly affected spatter generation. We focused our attention on the iron powder with the highest iron powder and found that FeO in its components greatly contributed to the welding rate.

That is, a flux containing 60% iron powder with FeO content varied in the range of 0.1 to 18%, C = 0.03%,
Si=0.01. Mn=0.30. P=
0.01%.

S = 0.01% shell filled with 21% 1,6 +nm
A wire with a diameter of φ metal powder-based flux was made.

FIG. 1 shows the measurement results of the welding efficiency of these wires in the downward welding position. Welding conditions are current 400A, voltage 32
V% welding speed 40 Ca1l/min, CCh gas flow 125
The welding speed of the wire was compared and examined by performing downward welding at a speed of 1/min and a distance between the chip bases of 1125 mm. The test plate was made of 5M-50B steel with a thickness of 20 mm and a width of 130 mm.
mm, and the length was 400 mm.

Experiments have shown that no improvement in the welding rate was found when the FeO content in the iron powder was less than 2.3%. This is thought to be because the filling flux contains a large amount of FeO in the iron powder, so that the insulating effect in the middle of the flux does not work effectively and the flux also has an energizing effect. In other words, if the current flowing through the wire is constant, the current flowing through the outer sheath of the wire is decreasing.

In other words, this means an increase in the diversion rate to the filling flux, which results in a decrease in the resistance heat generation of the wire sheath, which is thought to cause a decrease in the welding speed. On the other hand, if it exceeds 12.5%, the insulating effect of the flux increases and the resistance heat generation of the outer skin increases, but the CO reaction of the droplets at the tip of the wire becomes intense, increasing the amount of spatter and producing a large amount of slag. On the contrary, it causes a decrease in the amount of welding. Next, the influence of the amount of C in the outer skin on the amount of spatter was investigated. That is, using the flux shown in Table 1 and using various outer skins with varying amounts of C from o, aoa to 0.09%, wires of S mm 1φ were prepared, and the amount of spatter generated during downward welding was measured. .

Table 1 The results are shown in Figure 2. The welding conditions were the same as those used in the welding efficiency test. Note that spatter was collected using a copper sputter collection box. From the experiment, the integument C
When the amount is less than 0.01%, the GO reaction with oxygen in the arc atmosphere is reduced, resulting in a droplet detachment force at the tip of the wire. As a result, the size of the droplets increases, and the droplets do not transfer smoothly, eventually scattering around as large spatter particles.

On the other hand, if the amount of C in the outer skin exceeds 0.06%, the CO reaction becomes excessive and spatter generation tends to increase. Therefore, the amount of C in the outer skin is 0. The OI was set to 0.06%.

The above is the main structure of the wire of the present invention, but in order to improve bead formation by stabilizing the arc and adjusting the physical properties of a small amount of slag, SiO2, MnO, A203FaO, FeO
3. An oxide such as MgO can be added alone or in the form of a compound in an amount that does not exceed 10% in total. Mild steel is normally used for the wire sheath, but if low alloy steel or high alloy steel is used, the electrical resistance of the sheath will be greater, and therefore a further increase in the welding speed due to resistance heat generation can be expected.

In addition, the cross-sectional structure of the wire may be either an oven seam wire that has a seam on the circumference of the outer skin or a closed seam wire that does not have a seam on the circumference.
Seamless wire is desirable when considering robotization.

Further, as the shielding gas composition used when welding using the present invention, in addition to carbon dioxide gas, a mixture of carbon dioxide gas and oxygen gas or argon gas is also applicable. In the case of a mixed gas with argon gas, since the arc stabilizing effect of argon is superimposed, spatter can be further reduced. Next, the present invention will be explained in more detail using Examples.

[Example] Table 2 shows the flux compositions of the flux-cored wire of the present invention and the flux-cored wire prototyped for comparison.
Tables 3 and 4 show the results of welding tests using these wires. In Table 3.4, No. 1~
Na1l is an example of the present invention, and Nos. 12 to 17 are comparative examples. The wire sheath was a mild steel sheath and an alloy sheath shown in Table 2, filled with flux, and tested using a 1.6 mmφ wire with a seamless cross-sectional shape as a carbon dioxide shield. All of the examples of the present invention had a small amount of spatter, had high welding properties, and had good mechanical properties.

On the other hand, No. 12 wire has a small amount of metal powder, so the welding efficiency is not satisfied, and No. 13 wire has a large amount of C in the outer sheath, so No.
On the contrary, since the amount of C was small in No. 14, spatter occurred frequently in all cases.

In addition, No. 15 has a small amount of FeO in the iron powder, and No. 16 has an excessive amount of FeO, so No. 17 has a large amount of C and FeO.
Since both the amount of O is small, the welding speed decreases or spatter occurs frequently, so it cannot be used.

Table 2 [Effects of the Invention] As described above, the flux-cored wire for gas-shielded arc welding of the present invention generates less spatter and has high welding properties even when carbon dioxide gas is mainly used as the shielding gas, so it has higher efficiency. This makes possible welding. In other words, the practicality of this type of wire can be dramatically improved.

The value of the present invention is high as it responds to the automation, robotization, and high efficiency of welding.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between the amount of FeO in iron powder and the welding speed.
FIG. 2 is a diagram showing the relationship between the amount of carbon in the outer skin and the occurrence of spatter. Amount of spatter generated by other 4 people (g/min) Toko ω (mouth D 0 mouth welding speed (g/min)

Claims (1)

[Claims] 1. A flux-cored wire in which a steel sheath is filled with flux containing 90% by weight or more of metal powder, mainly iron powder, in an amount of 10 to 25% by weight of the wire, in which the amount of C in the steel sheath is 0.01 to 0.01. 0.06% by weight, an iron powder content of 41 to 87% by weight relative to the total flux, and a gas shielded arc characterized in that FeO in the iron powder is 2.3 to 12.5% by weight. Flux-cored wire for welding.