JPS5944959B2 - Sintered flux for horizontal submerged arc welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flux for horizontal submerged arc welding, and more specifically, it is used in combination with a welding wire made of a Ni-based alloy, significantly reduces the oxygen content in the weld metal, and provides an excellent machine. The present invention relates to a new composition of a flux for submerged arc welding that obtains excellent properties and forms a weld metal free of internal defects.

In recent years, LPG or LNG tanks have been constructed in various places, and horizontal submerged arc welding of low carbon Al-killed steel, 9% Ni steel, etc. is frequently performed, and its importance is increasing.

On the other hand, horizontal welding is welding in a special position, and basically has a factor that makes it easy to generate defects. For example, there is a problem that internal defects are likely to occur due to the fact that the solidification direction of the molten metal is downward. In other words, the columnar crystals generated on the upper plate side of the welded base metals that are butted together grow downward, so the blowholes generated in the upper half of the molten pool, the deoxidation products, or the molten material caught in the molten pool. It is difficult for the slag to float smoothly, preventing its escape, and internal defects are likely to occur. Furthermore, there is a problem in that the molten metal tends to sag due to gravity, which tends to cause undercuts, poor bead shapes, and poor fusion. Therefore, the present inventors
In order to solve this problem, based on the results of various studies on the composition of flux for submerged arc welding, we published JP-A-52-15.
In Japanese Patent No. 6145, a flux for horizontal submerged arc welding containing a large amount of fluoride was proposed. This is because when a large amount of fluoride is added to flux, the arc length becomes extremely short and the wire metal transfer takes on a short-circuit transfer type, but this phenomenon is extremely effective in preventing defects in horizontal welding. This is due to what has become clear. However, even with the above-mentioned flux, when austenite single-phase weld metal is formed with a wire made of a Ni-based alloy containing 40% or more Ni such as 4-conel or bus alloy, depending on how the deoxidizer is used, It has been found that the ductility of the weld metal is not necessarily satisfactory, and that there is a risk that minute defects that cannot be detected by X-ray inspection may remain inside the weld.

Therefore, in order to improve this, we conducted further studies and found that to solve the above problem, it is necessary to reduce the oxygen in the weld metal as much as possible, and to do so, we need to use a specific material in combination with fluoride. It has been found that adding a deoxidizing agent is extremely effective.

The present invention was made based on the above study results, and its gist is that CaF2,
2. A total of 20 to 80% of one or more of BaF2, NaF, AlF3 and MgF2 as a deoxidizing agent.
The particle size structure of the metal powder containing Al or both Al and Si in the range of 5% Al + 0.5 Si and 4% Si is finer than 100 mesh. % or more, a sintered flux for horizontal submerged arc welding is provided.

The present invention will be explained in detail below.

CaF2, BaF2, NaF in the flux of the present invention
, AlF3 and MgF2, one purpose is to stabilize the arc.

That is, as mentioned above, a large amount of fluoride has the effect of short-circuiting the wire metal transfer, which is effective in preventing the occurrence of spatter and slag entrainment in horizontal welding with an unstable molten pool. It is something. However, the effect of containing fluoride is not limited to this point; it is also possible to use specific deoxidizers such as 2.5 to 5.5% Al or 2.5% Al + 0.5Si <>5.5% Si. This is based on the discovery that when combined with 4% Al and Si, oxygen in the weld metal can be significantly reduced, and its mechanical properties and defect generation can be improved.

Normally, weld metal contains about 200 to 400 ppn of oxygen, but oxygen deteriorates the durability, ductility, or toughness of weld metal, especially in austenitic single-phase weld metal made of Ni-based alloy. NiO, an oxide of Ni, tends to precipitate at the grain boundaries, and when a large amount of Si exists, it promotes the precipitation of silicate at the grain boundaries, which embrittles the austenite grain boundaries and reduces the resistance. This leads to a decrease in cracking properties and ductility.

Therefore, it is extremely important to reduce the amount of oxygen in the weld metal, and the study results have revealed that it is necessary to reduce the amount of oxygen to 150 ppm or less in austenite single-phase weld metal.

By the way, fluoride itself is effective in reducing oxygen, and some fluxes in which Si is mainly added as a deoxidizing agent have been proposed in the past.

However, these combinations have weak deoxidizing power, making it difficult to reduce oxygen to 150 ppm or less;
Addition of an excessive amount of silicate promotes precipitation of silicate at austenite grain boundaries. Therefore, it was concluded that it was necessary to use a strong deoxidizing agent other than Si, so Ti, Al and Z
A study of r, etc. revealed that although Ti is effective in deoxidizing, it inhibits slag releasability and also deteriorates the bead appearance, and Zr increases susceptibility to solidification cracking. In the end, it was found that by using a specific amount of Al or A2 and Si in combination, good workability as a flux can be obtained and the most excellent deoxidizing effect can be exhibited.

The effects on workability include improving the conformability at the bead edges, stabilizing the arc, and preventing slag entrainment, blowholes, and spatter entrainment phenomena.

CaF2. BaF2, NaF, A2F, and MgF2
The effect in the present invention is obtained by using one or two of these fluorides.
This is obtained when the total amount of flux exceeds 20% of the total amount of flux, but if it exceeds 80%, the fluidity of the generated slag becomes excessive, resulting in irregular beads and a tendency to sag downward. Therefore, undercuts are likely to occur.
Figures 1 to 4 show fluorides such as CaF235%, BaF,
The results of an investigation into the properties of welds when horizontal submerged arc welding was performed with various amounts of Al and Si added as deoxidizers in a sintered flux containing 5% AIF, 8% AIF, and 8% AIF. This is an example.

For welding in this case, a Hastelloy alloy wire (2.4 maφ) having the composition shown in Table 1, W-1 was used, and 9% Ni steel shown in Table 2, S-1 was used as the base material.

FIG. 1 shows the relationship between the amounts of Al and Si in the flux and the amount of oxygen in the weld metal, and it can be seen that the oxygen amount is low in the shaded range, 150 ppm or less.

The straight line A in the figure shows the relationship between Al and Si in the flux.
l+0.5Si=2.5, and straight line B is Al
= 0.5, therefore, the shaded area is Al+0.5Si〉2.5% and Al'20.5%
It is shown by the inequality . FIG. 2 shows the results of taking a longitudinal bead bending test piece from the base metal surface position along the bead longitudinal direction, conducting a 180-type bending test, and investigating the presence or absence of cracks on the bent surface. According to this, a low oxygen content in the range of Al+0.5Si>2.5% is good, but on the other hand, when Al and Si are excessive, the bending ductility is impaired. That is, the straight line C in the figure (Al+0.5Si=5.5
) and to the left of D (Si=4),
It is the inequality Al+0.5Si 5.5%, Si:<4
Expressed in %. Figure 3 is below the plate surface 277!77
These are the results of an impact test conducted at -196°C on a two-notch Shalpi impact test piece taken from J.
Good results were obtained in the range of 4%. Furthermore, Figure 4 shows that the surface of each weld bead was ground by approximately 1v1t and dyed flaw detection was performed to investigate the presence or absence of defects such as minute blowholes or slag entrainment that are difficult to detect with X-ray transmission inspection. This is the result.

It can also be seen that a sound horizontal weld with few defects can be obtained in the range of 2.5% Al+0.5Si. An example of the study results in the present invention is as above, and as a result,
It is necessary to apply Al or Al and Si as a deoxidizing agent in the range of 2.5% Al + 0.5 Si + 5.5% Si + 4%.

By the way, CaF2, BaF2, NaF,
AlF3 and MgF2 are commonly used as welding materials, and either pulverized and sized ores or chemically synthesized materials can be used. Al and Si used as deoxidizing agents are their individual metal powders or F
It can be used as an alloy powder with other metals such as e-Al, Fe-Si, Si-Mn, and Al-Mg.

By the way, even if a deoxidizing agent whose type and amount are controlled in this way is added to the flux, the effect may not be obtained if the deoxidizing agent is unevenly distributed in the flux or has low reactivity. Therefore, it is impossible to obtain the excellent weld metal that is the object of the present invention. The present inventors have thoroughly studied countermeasures against such non-uniform distribution of the deoxidizing agent, and have determined that the metal powder containing Al and S1 added as a deoxidizing agent has a particle size structure finer than 100 mesh.
It was confirmed that it is necessary to contain 0% or more.

(Here, what is finer than 100 meshes is JlS
In other words, the deoxidizing agent is a metal, has a higher specific gravity than other raw material powders, and tends to be difficult to mix uniformly. If the particle size of the deoxidizing agent is too coarse, segregation will easily occur in the flux and the reactivity will also be low. Therefore, by making the particle size structure contain 70% or more of particles finer than 100 mesh, it will easily mix with other raw materials. It was revealed that the particles were evenly distributed even after granulation. This will be explained using an example.

That is, the Example flux F-1 (F
e-Al; 5.0% (50% Al), Fe-Si: 1.
5% (42% Si)), Fe-Al and Fe
- Varying the particle size of Si (4 levels) to produce four types of fluxes in the particle size range of 12 to 100 meshes, and then each of these fluxes to a narrower particle size range, namely 12 to 20, 20 to 32, 32 ~48,48~65,6
The distribution of the deoxidizing agent was investigated by sieving in five stages from 5 to 100 meshes.

That is, each sample was analyzed for Fe and ζ.
The addition of Fe to the flux is Fe-Si, Fe-A.
Since there is only 1, the analytical value of Fe in this case can be considered to be a relative indication of the distribution of Si and Al, and the results are as shown in FIG. From this result, the finer the particle size of the deoxidizing agent, that is, the more particles are finer than 100 mesh, the smaller the difference in Fe analysis value between each particle size range.
It can be seen that a value of 70% or more indicates a sufficiently uniform distribution. It goes without saying that the finer the reactivity of the deoxidizing agent, the better, and the greater the deoxidizing effect can be obtained.

Therefore, in the flux of the present invention, Al and Si
It is essential that 70% or more of the metal powder is finer than 100 mesh.
Other components of the above-mentioned essential materials are added as appropriate depending on the purpose of the flux, but the oxides include MgO, Al2O3, TiO2, SiO, MnO, C
aO, etc., and carbonates include CacO3MgCO3
etc. are added.

Further, as metal components, deoxidizers other than Al and Si, such as Mn, Ti to an extent that does not impair workability, and alloying agents such as MO, Cr, and W can be added as necessary.

By the way, the flux of the present invention is in the form of a sintered flux, but this is because it contains a deoxidizing agent, and for other components, it is possible to use molten flux that has been melted and ground in whole or in part. I can do it.

Granulation methods include kneading the raw material powder and water glass and then rolling granulation using a cylindrical or dish-shaped granulator, or mixing the raw material powder and water glass with a high-speed stirring blade mixer. Examples include a method of granulation.

The effects of the present invention will be further clarified by examples below. EXAMPLE Nine types of sintered fluxes having the compositions shown in Table 3, F-1 to F-9, were produced by granulating and sintering the mixed powder raw materials using water glass as a binder.

The granulation in this case was carried out by stirring and mixing using a high-speed stirring blade type granulator, and the firing conditions were 500'CX2hr.

Also, flats. After granulation, the waste is sized into a 12x100 mesh, with a bulk density (JlSK672l) of 0.90 to 1.0.
It was 0V/Cril. Among the fluxes in Table 3, F-
1 to F-5 are examples of the present invention, and F-6 and F-9 are comparative examples. Next, using fluxes F-1 to F-9,
Further, using the wires and steel plates shown in Tables 1 and 2, transverse submerged arc welding was performed using the combinations of fluxes, wires, and steel plates shown in the left column of Table 5. The groove shape, lamination procedure and welding conditions are as shown in FIG. 5 and Table 4. Welding on the back side was performed after welding on the front side was completed, and after lifting the back side using arc air gouging. As a result of the above welding,
That is, the evaluation of the bead appearance, the mechanical property test (longitudinal bead bending test, impact test) of the welded part, the dye penetrant test, and the oxygen analysis test were as shown in the right column of Table 5.

When fluxes F-1 to F-5 were used, good results were obtained in all cases due to the effects of the present invention.

- On the other hand, in Comparative Example A6, the amount of fluoride added was insufficient, and
Due to an inappropriate deoxidizing agent, the mechanical properties and dye penetrant testing were unsatisfactory. In the case of 7, the fluidity of the slag is large due to excessive fluoride, and the beads tend to sag.
In the final pass, an undercut occurred and a satisfactory horizontal bead appearance could not be obtained. Also, the addition of deoxidizing agent was inappropriate, and defects occurred in dye penetrant inspection and longitudinal bead bending test, as in case No. 6. In Comparative Examples Ya 8 and Ku 9, the particle size of the deoxidizing agent in the flux was coarse, and the effects of the present invention could not be obtained, so defects occurred in the longitudinal bead bending and dyeing flaw detection tests.

[Brief explanation of the drawing]

1 to 4 are graphs showing the relationship between the content of Al and Si in flux and the properties of weld metal, and FIG. 5 is a front view showing the groove shape and lamination procedure applied in the example. Figure 6 shows Fe-Al+Fe-S in flux.
It is a figure which shows the relationship between the particle size range of i and the Fe analysis value in flux.

Claims (1)

[Claims] 1 CaF_2, BaF_2,
One or two of NaF, AlF_3 and MgF_2
20 to 80% of total of species or more, 2.5% of Al or both Al and Si as deoxidizer ≦Al + 0.5Si
Contains in the range of ≦5.5% and Si≦4%, and A
A sintered flux for horizontal submerged arc welding, characterized in that the particle size composition of the metal powder containing L and Si is 70% or more of particles finer than 100 mesh.