JP2690046B2 - Self-shielded arc welding flux cored wire - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a self-shielded arc welding flux-cored wire, and more particularly to a self-shielded arc welding flux-cored wire with less spatter.

(Prior art and problem to be solved) Self-shielded arc welding Welding using flux-cored wire does not require external shielding gas, and because it is less adversely affected by wind, it requires pipes and wind protection measures. Since it is not necessary, it can be said that welding preparation is simple and most suitable for outdoor welding.

However, a drawback is that a large amount of spatter and fume are generated, and these adhere to the welded portion and impair the appearance of the welded portion. Fume is easy to remove, but sputter is not easy to remove because many are fused. Also, it is not preferable in terms of workability.

As described above, since the conventional self-shielded arc welding flux-cored wire requires a lot of man-hours for removing spatter, it is a fact that development of a wire with less spatter is desired.

The present invention has been made in order to meet such a demand, and an object of the present invention is to provide a self-shielded arc welding flux-cored wire with less spatter generation and good welding workability.

(Means for Solving the Problem) In view of the above problems, the present inventor has sought to find out the cause of the increase in spatter generation particularly in the conventional wire, and the migration of droplets has a great influence. Since it has been found, as a result of further intensive research on its countermeasures, the present invention has been made here.

That is, the self-shielded arc welding flux-cored wire according to the present invention has a steel shell, an enzyme: 20 to 80 ppm,
Cr: 0.01-0.10wt%, C ≦ 0.05wt%, Si: 0.02-0.30wt%
And Mn: 0.2-1.5 wt%, and if necessary, N ≦ 5
It is characterized in that it is made of steel regulated to 0 ppm, and that the cavity surrounded by the steel outer shell is filled with flux.

 Hereinafter, the present invention will be described in more detail.

(Operation) First, the results of studying the cause of increased spatter generation in the conventional self-shielded arc welding flux-cored wire will be shown.

FIG. 1 shows the relationship between the droplet diameter and the amount of spatter generated, and is the data obtained with self-shielded arc welding flux-cored wires having different fluoride compounding ratios. Welding conditions are wire diameter 1.6mmφ, DCEN, 250A-23V,
Welding was performed downward on a flat plate with a protruding length of 25 mm, a running speed of 25 cm / min, and a receding angle of 15 °. The droplet size during welding was measured using a high speed camera.

From FIG. 1, a clear correlation is observed between the droplet size and the amount of spatter generated, and a significant reduction in spatter is observed when the droplet size is 2.5 mm or less. The droplet diameter becomes 2.5 mm or less when the amount of fluoride added to the flux is 15% or less, but it becomes insufficient on the shield surface and pits and blowholes are generated, resulting in a sound weld. I couldn't get it. Also,
It was observed that the generation of spatter was due to the large growth of the droplets and the droplets flying out due to the arc force. Since the arc is generated from the tip of the droplet, as the droplet grows,
The arc length gradually decreases and the arc voltage decreases. The decrease in arc voltage is not only a cause of spatter generation but also a cause of impairing workability because droplet transfer is not stable. Therefore, it has been found that by suppressing the growth of droplets, it is possible to stabilize the fluctuation of the arc voltage, which is effective in improving workability and suppressing spatter.

Therefore, since the refinement of the droplet size is effective in reducing spatter and improving workability, various factors other than fluoride were investigated, and as a result, Cr, oxygen content, etc. in the hoop were dissolved. It was found to be effective in making the droplets finer.

FIG. 2 shows the droplet diameters investigated using self-shielded arc welding flux-cored wires in which the fluxes having the compositions shown in Table 1 are contained in hoops having different Cr and oxygen contents. The welding conditions are the same as in the case of FIG.

FIG. 2 shows that the regulation of Cr and oxygen contents is effective for making the droplet size smaller. That is, the effect of Cr differs depending on the amount of oxygen in the hoop, but by adding only 0.01% of Cr, the droplet size becomes about 15 to 20% smaller, and as the Cr content increases, the droplet size can be made smaller. Recognize. However, if 0.1% or more of Cr is added, no further effect can be obtained. On the other hand, the increase in oxygen content has the effect of reducing the droplet size even if the Cr content is the same. Oxygen and Cr content in the hoop to obtain a droplet diameter of 2.5 mm or less, which can be expected to greatly reduce the amount of spatter, Cr: 0.02% or more when oxygen is 20 ppm, Cr: 0.01% or more when oxygen is 50 ppm When oxygen is 80ppm, Cr: 0.008% or more.

As a result of further detailed experiments on various components of the hoop based on the above findings, the present invention wire was found.

 Next, the reasons for limiting the components of the wire of the present invention will be described.

(1) Oxygen Increasing the amount of oxygen lowers the surface tension of the droplet, promotes its detachment, reduces the droplet diameter, and is effective in reducing spatter. For that purpose, 20 ppm or more is required. However, if it exceeds 80 ppm, mechanical properties such as toughness deterioration will occur, so the oxygen amount is preferably in the range of 20 to 80 ppm. This oxygen content is the total oxygen content of the steel skin.

(2) Cr The increase in Cr content lowers the vapor pressure of the oxide on the surface of the suspended droplets due to slag evaporation, and reduces the repulsive force of the arc.
It assists the detachment of droplets and is effective in reducing spatter as well as increasing the amount of oxygen. For that purpose, 0.01% or more is required, but if it exceeds 0.10%, the further effect cannot be obtained, the strength of the wire becomes high, and the productivity is deteriorated, so the Cr content is 0.01 to 0.10%. Ranges are preferred.

(3) CC Since the explosion of CO and CO ₂ gas in droplets having a C content of more than 0.05% increases and spatter increases, it is preferable to control C ≦ 0.05%.

(4) Si, Mn Si, Mn suppresses CO and CO gas in droplets and is effective in reducing sputtering. For that purpose, Si is added 0.02-0.30%,
If it exceeds 0.30%, the workability of the wire is poor and the strength of the deposited metal increases, which is not preferable. Also, Mn is 0.2-
Although it is added at 1.5%, if it exceeds the upper limit, the same adverse effect as that of Si is exerted, which is not preferable.

(3) N N not only causes the formation of pits and blow holes, but also impairs the performance of the deposited metal.
It is desirable to suppress it to 50 ppm or less if necessary. This amount of N is the total N of the steel skin.

The above-mentioned effects are not affected by the wire cross-sectional shape, flux composition, wire size, etc.
There are no particular restrictions on these conditions.

 Next, examples of the present invention will be described.

(Example) Using a test wire (1.6 mmφ, flux rate 20%) in which the flux shown in Table 1 was included in the mild steel hoop having the composition shown in Table 2, DCEN, 250A-23V, protruding length 25 mm,
Welding experiments were conducted under the welding conditions of traveling speed 25 cm / min and receding angle 15 ° to investigate the performance. The results are shown in Table 2.

As is clear from Table 2, No. 1 to No. 4 of the examples of the present invention
Generated less spatter and had good workability.

On the other hand, in Comparative Examples No. 5 to No. 13, good results were not obtained because the hoop component was outside the range of the present invention. Note that N
No. 6, No. 11, and No. 12 have less spatter generation and good workability, but are not preferable because they have a problem in wire workability.

(Effects of the Invention) As described in detail above, according to the present invention, since the oxygen, Cr amount, etc. are defined in the self-shielded arc welding flux-cored wire, a wire with less spatter generation and good workability can be provided. Can be provided. Moreover, since there is no problem in wire processing, the practical effect is great.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the droplet size and the amount of spatter generated, and FIG. 2 is a diagram showing the relationship between the outer skin components (oxygen and Cr amounts) and the droplet size.

Claims (2)

(57) [Claims] 1. A steel outer shell has oxygen: 20-80 ppm, Cr: 0.01-
0.10 wt%, C ≦ 0.05 wt%, Si: 0.02-0.30 wt% and Mn: 0.
A self-shielding arc welding flux-cored wire comprising a steel containing 2 to 1.5 wt% and having a cavity surrounded by the steel shell filled with flux. 2. The self-shielding arc welding flux-cored wire according to claim 1, wherein the steel contains N ≦ 50 ppm.