JPH06104279B2 - Composite wire for self-shielded arc welding - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a composite wire for self-shielding arc welding applied to outdoor all-position welding of ships, bridges, marine structures and the like.

[Conventional technology]

Unlike other welding materials, the self-shielding arc welding composite wire (hereinafter referred to as the self-shielding wire) has a strengthened self-shielding mechanism, so there are few welding defects due to wind, so it is especially suitable for outdoor field construction. Has been adopted.

However, a large amount of deoxidizing agents and denitrifying agents such as Al and Mg are added to the conventional self-shielded wire to prevent the generation of pores in the deposited metal. However, the crystal grains became coarse, and good low temperature toughness could not be obtained. Furthermore, with conventional self-shielding wires that have used CaF ₂ as the main metal fluoride, CaF ₂ has a problem of bead formation in the vertical position and the vertical position because it significantly increases the fluidity of slag. It was difficult to apply it to the on-site construction, which requires high performance.

In order to solve these drawbacks, for example, JP-A-58-1480
As disclosed in Japanese Patent Publication No. 95, there is a self-shielding wire that has a reduced diameter and is used for all-position welding with good use characteristics and improved porosity resistance and low temperature toughness. The wire shown therein uses BaF ₂ as a metal fluoride, and by further reducing the diameter, the low temperature toughness and all-position weldability are certainly improved compared to the conventional wire, but especially the slag in the narrow groove is improved. It is not always satisfactory in terms of peelability, bead appearance, and shape.

[Problems to be solved by the invention]

The present invention has been made for the purpose of eliminating the above-mentioned drawbacks of conventional wires and expanding the field of application, and has good all-position weldability and low-temperature toughness as well as slag peeling and beading in a narrow groove. The purpose of the present invention is to provide a self-shielding wire having an excellent appearance and shape.

[Means and actions for solving problems]

The features of the composite wire for self-shielded arc welding according to the present invention are: BaF ₂ : 35-70 wt%, LiF: 3-15 wt%
_{%, SiO 2: 0.2~3.5wt%,} CaO: 0.4~5.8wt%, iron oxide:
4-28wt%, Al: 4-15wt%, Mg: 3-12wt%, Mn: 2-9wt%
That there is a particulate flux containing, as essential components in that filling 13～30Wt% of the wire the total weight in the steel sheath, SiO ₂ and Ca is a particulate, particularly part or all is fused and crushed
By using O, it is possible to further improve the flaking property, the bead appearance, and the shape of the slag in the narrow groove.

The reason why the self-shielding wire according to the present invention has the above configuration will be described in detail below.

The role of metal fluorides used in large amounts in self-shielding wires is to cover the weld metal as a slag agent to improve the bead shape, shield the arc and molten pool from the atmosphere as gas generating substances, and degassing elements. Is to bring out the full effect of. In the present invention, BaF ₂ is contained in an amount of 35 to 70 wt% because the BaF ₂ has better shielding property and droplet transfer property than the conventionally used CaF _2, etc. This is because the slag has excellent characteristics in encapsulation and bead formation in a posture. When BaF ₂ is less than 35 wt%, these characteristics are not sufficiently exhibited, while when it exceeds 70 wt%, the arc becomes unstable, and the amount of slag produced becomes excessive, and defects such as slag entrainment are likely to occur. Therefore, the proper range of BaF ₂ is 35 to 70 wt%.

In the present invention, 3 to 15 wt% of LiF is further added, and the purpose is to improve the porosity resistance and low temperature toughness of the deposited metal.
LiF is easily vaporized by the welding arc heat to form a high-pressure atmosphere, which effectively shields the droplet from the outside air. In addition, Li ions generated by thermal decompression make the arc extremely stable and smooth the droplet transfer, so that the absorption of droplets and ambient air in the molten pool is minimized and the amount of nitrogen in the deposited metal is reduced. Further, it is a deoxidizing and denitrifying agent due to the above effect.
The amount of Al added can be reduced, the amount of Al in the deposited metal can be reduced, and the low temperature toughness can be improved. If the LiF content is less than 3 wt%, the above effect is not obtained. On the other hand, if it exceeds 15 wt%, the arc becomes unstable due to excessive high-pressure steam, and spatter frequently occurs, which is not preferable. Therefore, the proper range of LiF is 3 ~ 15wt%
And

The conventional self-shielding wire containing BaF ₂ as a main component had a problem in slag peelability in all-position welding, especially in narrow groove welding. Therefore, it takes a long time to remove the slag, the work efficiency is lowered, and the slag remaining in the groove cannot be completely melted by the next pass, so that welding defects such as slag inclusion easily occur. Further, the appearance and shape of the beads, particularly the familiarity with the base material, were poor, and there was a problem in fatigue strength.

In the present invention, SiO ₂ and CaO are used as essential components because the slag in the narrow groove and the bead appearance and shape are improved.

SiO ₂ has a function of smoothing the bead surface and forming a glossy bead, thereby facilitating separation of the encapsulated slag from the bead surface. Further, it has the effect of improving the flow of the bead and improving the bead shape, especially the familiarity with the base material. If SiO ₂ is less than 0.2 wt%, the above effect does not occur, and conversely 3.5
If it exceeds wt%, Si reduced by the strong deoxidizers Al and Mg
Is excessively retained in the deposited metal, coarsens the crystal grains, and reduces the toughness, which is not preferable. Therefore, the proper range of SiO ₂ is 0.2 wt% to 3.5 wt%.

CaO is also a component effective in improving the slag toughness. That is, CaO has an action of reducing the binding force between the bead surface and the solidified slag, especially in a slag system containing BaF ₂ as a main component, and makes it easy to break the slag encapsulated in the bead surface even in narrow groove welding. This characteristic has a larger effect better when coexisting with SiO ₂ than single addition of CaO. 0.4wt
% Or less, the above effect cannot be expected, and if it exceeds 5.8 wt%, the bead shape becomes convex and the arc becomes unstable, so that it cannot be adopted. The proper range of CaO is
0.4 wt% to 5.8 wt%

It should be noted that, although it is a raw material of SiO ₂ and CaO, the SiO ₂ source may be silica sand, feldspar, wollastonite, or an oxide such as K ₂ SiO ₃ or Li ₂ SiO ₃ . In addition, quick calcium (C
aO) is not preferable because it is a material that easily absorbs moisture, and lime (CaCO
₃ ) is not recommended, because if a certain amount or more is added, spatter frequently occurs and workability deteriorates. Wollastonite (CaO ・ SiO ₂ )
And calcium ferrite (CaO.Fe ₂ O ₃ ) are preferably used in a more stable manner against moisture.

It is the SiO _2, SiO _2, further effective to use a composition pre beforehand melted crushed CaO as CaO raw material is HanTsuta. That is, a composition obtained by melting a flax raw material containing SiO ₂ and CaO in an electric furnace or the like and then pulverizing it has a melting point lower than that of a single component, thereby increasing the fluidity of the molten slag and improving the slag encapsulation property. As a result, the action of weakening the bonding force between the bead surface and the slag increases. For this reason, the slag peeling in the narrow groove becomes much better than in the case where the raw materials of SiO ₂ and CaO are added in combination. Further, when the wire is melted, the raw material does not undergo severe dissociation, expansion or explosion due to reaction, so that the arc is always stable and the occurrence of spatter is reduced. The addition range of the composition obtained by previously melting and pulverizing SiO ₂ and CaO may be such that the respective components are within the ranges described above. For example, the SiO ₂ and CaO components may be replaced with the composition in which the total amount is previously melted, or only a part thereof may be replaced.

In the present invention, iron oxide is an essential component, the reason is
Firstly, oxygen is supplied to the molten metal excessively deoxidized by Al-Mg to promote the nucleation of ferrite and improve the toughness of the weld metal. Secondly, since iron oxide has a low melting point, high melting point Al ₂ O ₃ or MgO produced by the deoxidation reaction of Al-Mg is levitated as slag to prevent welding defects such as slag inclusion. This is because it is possible. Thirdly, since the addition of iron oxide provides a suitable slag fluidity for all-position welding, it is useful for improving the bead appearance and shape and enhancing the slag shield. . If the iron oxide content is less than 4% by weight, the above effect is not obtained, while if it exceeds 28% by weight, the droplet transfer property is deteriorated and defects such as slag entrainment due to excessive slag are likely to occur, which is not preferable. Therefore, the proper range of iron oxide is 4 to 28 wt%.

The iron oxide may be an oxide represented by FexOy, for example, FeO, Fe ₂ O ₃ , Fe ₃ O ₄ , or the like, or may be added in the form of MxFeyOz or an alkali or alkaline earth metal oxide. Complex oxides with substances (eg LiFeO ₂ , NaFe
O ₂ , CaFe ₂ O ₄ , Sr ₂ FeO ₄ , Sr ₂ Fe ₂ O ₅ , Sr ₆ Fe ₁₀ O ₂₂ , BaFe ₂ O
₄ , BaFe ₁₂ O ₁₉ etc.) can also be added.

As a strong deoxidizing and denitrifying agent, Al has the effect of improving the porosity resistance of the weld metal and is an essential element for self-shielding wires. If it is less than 4% by weight, the above effect is insufficient and welding defects such as pits and blowholes occur.On the other hand, if it exceeds 15% by weight, the amount of Al in the weld metal becomes excessive, causing coarsening of crystal grains and deterioration of toughness. It is not preferable because it causes. Therefore
Al is 4 to 15 wt%. In addition, Al may be used alone, or Fe-Al, Al-Mg, Zr-Al, Li-Al, Ca-Al, Ca-Al.
It may be added in the form of an alloy such as Mg.

Mg is a strong deoxidizer and an element that improves the migration of droplets. Addition of Mg makes the droplet particles finer, resulting in spray-like droplet transfer. If the Mg content is less than 3 wt%, the above effect is insufficient, and if it exceeds 12 wt%, the occurrence of spatters and an increase in fumes are not preferable. Therefore, the proper range of Mg is 3-12 wt%. Incidentally, Mg may be used alone or may be added in the form of Mg alloy such as Al-Mg, Ni-Mg, Li-Mg, Ca-Mg.

The reason why the amount of Mn added is set to 2 to 9 wt% is to give necessary and sufficient strength suitable for the welded joint. If it is less than 2 wt%, the required strength and good bead shape cannot be obtained, while if it exceeds 9 wt%, the strength becomes too high and the crack resistance deteriorates. Therefore, the amount of Mn added is 2 to 9 wt%. In addition, Mn may be used alone, or may be used in the form of various alloys including iron alloys such as Fe-Mn, oxides such as MnO, and complex oxides such as Li ₂ MnO ₂ .

Above it is an essential component of the granular Furatsukusu in the wire of the present invention, Li ₂ CO ₃ in further enhancing means shielding effect in the present _{invention, Na 2 CO 3 BaCO 3,} CaCO 3, SrCO 3, MGCO 3, MnC
Add metal carbonate such as O ₃ within a range that does not cause workability deterioration such as frequent occurrence of spatter, and CaO, Al ₂ O ₃ , MgO, K ₂ O, Na ₂ O, TiO as a physical property modifier for slag. ₂ , oxides such as ZrO ₂ and fluorides such as CaF ₂ , SrF ₂ , NaF and K ₂ SiF ₆ may be added if necessary.

In addition, low temperature toughness (-20 ℃ to -40 ℃), especially for offshore structures.
Ni, Ti, Z when applied to the required field
Elements such as r and B may be added to further improve the low temperature toughness.

In the self-shielding wire of the present invention, the ratio of the powdery granules filled in the steel sheath is set to 13 to 30 wt%. If it is less than 13 wt%, the above-mentioned various effects of the flux cannot be expected, and pores may be generated in the weld metal or the slag encapsulation effect may be impaired. Conversely, if it exceeds 30 wt%, the amount of slag produced is large. This is because, as a result of excessive passage or an increase in the amount of alloying components and Al in the weld metal, it is difficult to obtain the required mechanical properties, and the wire drawing workability deteriorates, making wire production difficult.

The material of the steel sheath of the wire of the present invention is usually mild steel, but low alloy steel and high alloy steel can also be used depending on the application. The wire size is preferably 2.4 mm or less from the viewpoint of use characteristics and weldability in all positions. Also,
Regarding the cross-sectional shape of the wire, it is difficult to draw a wire with a complicated cross-section as shown in FIG. 1A, and the wire may be twisted or directional to deteriorate the wire feeding property. Therefore, it is preferable to use a simple cross section such as (B), (C), (D), or (E) from the viewpoints of wire drawing workability and wire feedability.

〔Example〕

The effects of the self-shielding wire according to the present invention will be described more specifically by way of examples.

Table 1 shows the prototyped 2.0 mm self-shielding wire.
The results of the welding performance investigation are shown in Table 2.

The wires satisfying the conditions of the present invention (No. 1 to No. 6) have excellent low temperature toughness as shown in Table 2 and good workability in all postures (slag flaking, bead appearance, shape). There is.

On the other hand, No. 7, No. 8 wire BaF ₂ does not meet the requirements of the present invention, there is a drawback in workability in all postures, No. 9,
The wire of No. 10 has a problem particularly in arc stability because LiF does not meet the requirements of the present invention. No. 11 is SiO ₂ , CaO
Since the slag content is small, the slag is poorly cracked, and No. 12 and No. 13 have low-temperature toughness and bead shape due to excessive SiO ₂ and CaO, respectively. In No. 14 and No. 15, iron oxide does not satisfy the requirements of the present invention, and there is a problem in bead shape and X-ray performance. Al,
No. 16 with a small amount of Mg has many pores, No. 17 with an excessive amount of Al has extremely deteriorated low temperature toughness, and No. 18 with an excessive amount of Mg has a problem in arc stability. Furthermore, the wires of No. 19 and No. 20 in which Mn does not satisfy the requirements of the present invention cannot be adopted because of insufficient strength and insufficient low temperature toughness, respectively.

[Advantages of the Invention] As described above, the self-shielding wire of the present invention solves the conventional problems, is excellent in low temperature toughness, and has good all-position welding workability (especially slag peeling property and bead appearance,
Since the shape can be obtained, it greatly contributes to the expansion of the application field of self-shield welding.

[Brief description of drawings]

 1 (A) to (E) show cross-sectional views of the composite wire.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsukasa Yoshimura 5-10-1, Fuchinobe, Sagamihara-shi, Kanagawa, Nippon Steel Corp. 2nd Technical Research Institute (56) References Japanese Patent Publication No. 52-5022 (JP, B2)

Claims (2)

[Claims] 1. BaF ₂ : 35 to 70 wt% LiF: 3 to 15 wt% SiO ₂ : 0.2 to 3.5 wt% CaO: 0.4 to 5.8 wt% Iron oxide: 4 to 28 wt% Al: 4 to 15 wt % Mg: 3 to 12 wt% Mn: 2 to 9 wt% Powder-granular flux, which is an essential component, is filled in a steel sheath in an amount of 13 to 30 wt% of the total weight of the wire. Composite wire for arc welding. 2. The composite wire for self-shielded arc welding according to claim 1, wherein SiO ₂ and CaO are partially or wholly melted and pulverized into powder particles.