JP3523010B2 - Flux-cored wire for primer-resistant gas shielded arc welding - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flux-cored wire for gas shielded arc welding, which is used in the field of building welded structures such as ships and bridges, and is particularly suitable for horizontal fillet welding to obtain good primer resistance. Hereinafter referred to as flux-cored wire).

[0002]

2. Description of the Related Art In fields such as shipbuilding and bridges, the proportion of horizontal fillet welding is high, and most steel materials are coated with a primer (rust preventive paint) to prevent rust during construction. Weld defects such as pits and gas grooves tend to occur during welding of steel sheets. To prevent this, removal of the primer before welding, reduction of the welding speed, or repair of the defective portion after welding increases man-hours and reduces welding work efficiency.

Conventionally, various flux-cored wires for improving the primer resistance in horizontal fillet welding have been proposed. For example, the proposal of Japanese Patent Laid-Open No. 61-147993 is to increase the stirring of the molten metal pool to facilitate the release of the primer pyrolysis gas by containing a metal fluoride or a metal carbonate. JP-A-1-262
Japanese Patent Publication No. 096 describes a flux-cored wire that uses a hydrogenated substance of a metal or a metal alloy, optimizes the type and amount of a slag forming agent, has good primer resistance and a bead shape, and has little spatter. JP-A-52-680
No. 40, JP-A No. 52-144341, and the like propose that a predetermined amount of hydrogen is supplied from a shield gas or a filling flux to accelerate the gas release rate in the molten metal and to supply the gas before solidification of the molten metal. The emission is intended to prevent welding defects such as pits and gas grooves.

However, when a large amount of metal fluoride is contained, the viscosity of the molten slag is reduced, and the slag remains thin on the standing plate side of the horizontal fillet beads, and the removal thereof, that is, the slag removability becomes a problem. . Since the metal carbonates are more likely to generate spatters and increase the man-hours for removing the spatters attached to the welded portions, the content thereof is limited. Further, in the high hydrogen type flux-cored wire, the steel type and the plate thickness are limited in view of the welding speed and the crack resistance of the weld metal.

Further, in the case of ships and bridges, from the viewpoint of fatigue strength, a horizontal fillet bead shape without undercuts or overlaps is required, and if they occur, restoration of these beads will significantly reduce work efficiency.

[0006]

Therefore, the present invention is for primer-resistant gas shielded arc welding for which the arc resistance is stable, slag can be easily removed, and a good horizontal fillet bead shape can be obtained together with the improvement of the primer resistance. It is intended to provide a flux-cored wire.

[0007]

SUMMARY OF THE INVENTION The gist of the present invention is a flux-cored wire for gas shielded arc welding in which a steel shell is filled with flux, and the weight percentage of the total weight of the wire is TiO ₂ : 2.0. _{~5.0%, SiO 2: 0.2~0.6%} , ZrO 2: 0.2~0.8%, iron oxide: 1.0~3.5%, Ca: 0.03~0 It is a flux-cored wire for gas-shield arc welding, which has a resistance to primer of 30% and F: 0.005 to 0.05%, and has a total hydrogen content of 20.
It is a flux-cored wire for gas shielded arc welding with excellent primer resistance that is limited to ppm or less.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION When a conventional primer-corrosion resistant flux-cored wire is used, considerably high speed welding is possible with a steel sheet coated with an inorganic zinc primer, but a steel sheet coated with a wash primer is often used in the field of bridges. At the welding site, the welding speed is approximately 30 cm / min because the thickness of the wash primer varies and the plate thickness is large and the cooling rate increases.
If it exceeds, the frequent occurrence of pits and gas grooves becomes a problem. The present inventors, in particular, for the purpose of improving the primer resistance in horizontal fillet welding of wash primer-coated steel sheet, as a result of examining various flux-cored wires in detail and examining them, the present invention was obtained with the following findings. It has been completed.

[0009] In the present invention, TiO _2, SiO ₂ and ZrO ₂ is established a encapsulated with bead shape the entire bead surface,
Further, the slag is made to have a certain thickness and is contained as a slag forming agent for facilitating the removal of the slag. Further, the slag composition containing iron oxide and CaO was used to expand the molten pool, and the content of iron oxide was increased to show the results in FIGS. 1 (a), (b), and (c). As described above, the solidified unevenness was intentionally formed in the generated slag.

FIG. 1 (a) is a schematic view of the bead surface,
The thick portion 6 and the thin portion 5 of the slag are shown, (b) shows the BB cross section of (a), (c) shows the CC cross section of (a), and the cross sectional thickness of the slag 4 on the surface of the bead 3 is shown. Shows the difference.
That is, the discharge of the primer combustion gas to the outside is promoted by intermittently forming the thin portion 5 of the slag layer 4 to the extent that the surface of the bead 3 is not exposed as the molten pool expands. In addition, F was limited to a small amount to weaken the arcing force and suppress the melting of the corner portion to reduce the amount of primer combustion gas generated. It was also confirmed that the primer resistance can be further improved by reducing the total hydrogen content of the flux-cored wire itself as much as possible. Even if it is a wash primer coated steel sheet, the welding speed is 4
It was found that pits and gas grooves can be significantly reduced at 0 to 45 cm / min.

At this time, iron oxide stabilizes the arc to reduce spatter, and there is no overlap of the toe of the lower plate bead to form a bead having good compatibility with the base metal.
The slag having a composition containing CaO was brittle and easily crushed, and effectively acted to facilitate slag removal.

The reasons for limiting the components of the flux-cored wire of the present invention will be described below. [TiO ₂ : 2.0 to 5.0%] TiO ₂ forms a slag that covers the entire bead surface, secures a smooth bead shape and a certain amount of slag, and facilitates slag removal. It is contained at 2.0% or more. TiO ₂ is 2.
If it is less than 0%, the amount of slag produced is insufficient, the encapsulation effect of the slag is insufficient, the bead shape and appearance are inferior, and the bead is partially exposed, and removal of the slag becomes difficult. On the other hand, when TiO ₂ exceeds 5.0%, the amount of slag generated is large and the viscosity of the molten slag is too high, so that the uneven solidification of the molten slag as shown in FIG. 1 is not formed and the gas is released. It becomes obstructed, and gas grooves are likely to occur as well as pits. In addition, the bead toe portion overlaps.

[SiO ₂ : 0.2-0.6%] SiO ₂
Is contained in an amount of 0.2% or more as a slag forming agent to obtain a slag composition having a good slag encapsulation property. On the other hand, SiO ₂ is less than 0.
If it exceeds 6%, the viscosity of the slag becomes large, uneven solidification of the molten slag hardly occurs, and the primer resistance deteriorates. In addition, the bead has a rounded shape, which makes the toe portion less compatible.

[ZrO ₂ : 0.2-0.8%] ZrO ₂
Is contained as a slag forming agent in an amount of 0.2% or more, a slag encapsulating the entire bead is formed and the bead shape is adjusted. If ZrO ₂ is less than 0.2%, the molten slag tends to flow and the leg length of the bead on the standing plate side becomes small. Further, the uneven solidification of the molten slag becomes excessive and the bead is partially exposed, which makes it difficult to remove the slag. On the other hand, ZrO ₂ is 0.8%
Beyond that, the bead becomes thin and convex, and it becomes a slag that is dense, hard and difficult to break, and it becomes difficult to remove the slag. In addition, solidification is fast and uneven solidification is less likely to be formed.

[0015] [Iron oxide: 1.0 to 3.5%] in the present _{invention, FeO, Fe4 3 O 4,} Fe 2 O 3 iron oxide such is contained more than 1.0%. By including a relatively large amount of iron oxide in the slag composition together with CaO, the viscosity of the slag is reduced. As a result, it became possible to easily release the primer pyrolysis gas to the outside and effectively expand the molten pool and form uneven solidification of the molten slag to improve the primer resistance. The formation of the solidification unevenness of the molten slag becomes stronger with the increase of iron oxide, but this is possible in the presence of CaO. Further, the iron oxide has a stable arc state, reduces the occurrence of spatter and has good compatibility with the base material, and acts to form a uniform bead toe shape.

If the iron oxide content is less than 1.0%, these effects cannot be obtained. On the other hand, if the iron oxide content exceeds 3.5% by weight, the amount of slag produced becomes excessive, and intermittent thin slag due to uneven solidification of the molten slag. It becomes difficult to form a layer, and the primer resistance rapidly deteriorates. Further, when the viscosity of the slag is excessively decreased, the slag encapsulation property on the bead standing plate side is deteriorated and undercut occurs, and the slag is difficult to be separated from the bead surface, and the slag is also difficult to remove.

[Ca: 0.03 to 0.30%] Ca is C
To obtain a slag composition containing aO, 0.03 to 0.
Contains 30%. The molten slag of this composition, combined with iron oxide, reduces the viscosity and expands the molten pool.
It is also essential for forming uneven solidification of the molten slag. Further, the solidified slag is brittle and easily broken, and easily peeled off from the bead surface, so that the slag can be easily removed. In addition, in the case of a slag composition containing a considerable amount of iron oxide and not containing CaO, the bead toes tend to overlap. The effect of Ca is obtained by containing 0.03% or more. On the other hand, when Ca exceeds 0.30%, CaO becomes an excessive slag composition, uneven solidification of the molten slag is less likely to be formed, and seizure on the bead surface of the slag becomes visible, which makes it difficult to remove the slag. .

In the present invention, the raw material containing Ca is not particularly limited, but in addition to the simple substance of Ca,
For example, when an alloy such as Ca-Si or a molten flux containing CaO, Ca oxide and carbonate, calcium stearate, or the like is contained, the Ca conversion value thereof is regarded as the content. Ca adhering to the inside and outside surfaces of the steel shell and the steel shell is included in the content, but CaF ₂ has a small effect of including CaO in the slag composition, and is excluded from the Ca content limited in the present invention. To do.

[F: 0.005 to 0.05%] F has an effect of preventing the formation of pits and gas grooves by facilitating the release of gas by the stirring action in the molten metal in order to improve the primer resistance as compared with the prior art. It is used as an essential ingredient. On the other hand, F strengthens the arc force, increases the penetration of the corner portion, and increases the combustion amount of the primer. In particular, in the case where a large amount of primer pyrolysis gas is generated, such as a wash primer, it is advantageous to improve the primer resistance by reducing the F content as much as possible to prevent excessive penetration. Therefore, F is limited to 0.005 to 0.05%. Within this range, the viscosity of the slag is adjusted without deteriorating the primer resistance to make the fillet bead shape smoother, and
Improves the conformability between the bead toe and the base material. If F exceeds 0.05%, in addition to the increase in the penetration at the corners, it is difficult to form appropriate solidification unevenness of the molten slag, and the slag remains thin at the bead toe on the standing plate side, which has adverse effects. appear. F may be contained in a fluoride of Li, Na, K, Mg, Ca, or K ₂ SiF _6, etc., and the content is expressed by the F conversion value of these.

[Total amount of hydrogen in wire: 20 ppm or less] Hydrogen in the wire raises the hydrogen partial pressure in the arc atmosphere together with hydrogen by the primer pyrolysis gas and penetrates into the molten metal, causing pits and gas grooves. Becomes In order to suppress the generation of pits and gas grooves due to this hydrogen, it is necessary to minimize the total amount of hydrogen contained in the filling flux, the wire contained in the steel shell and attached to the inner surface of the steel shell. There is. The total amount of hydrogen in the wire can be reduced by 20 ppm or less by appropriately selecting the kind of the flux raw material, the drying condition of the filling flux, or, in the case of the seamless type flux-cored wire, the intermediate annealing condition of the wire. As a result of investigating the influence of the trial wires in which the wire components were made almost the same and the total hydrogen content was changed, the primer resistance was further improved by setting the total hydrogen content of the wire to 20 ppm or less. The total amount of hydrogen in the wire is measured by an inert gas fusion heat conduction method after removing water and lubricant (these effects are extremely small for the primer resistance) adhering to the wire surface. Assumed to be performed.

The reasons for limiting the components essential to the flux-cored wire of the present invention have been described above. Other wire components are C, which is a basic component mainly for ensuring the strength and toughness necessary for the weld metal. (0.02-0.10%), Si
(0.2 to 1.5%), Mn (1.0 to 4.0%), K and Na for arc stabilization (0.02 to 0.10% in total of one or two). And iron powder for obtaining high weldability. In addition, in (), mild steel and 490 N /
The preferable range of the content of the flux-cored wire for mm ² class high-strength steel is shown.

Further, a slag forming agent such as Al ₂ O ₃ , MgO and MnO and a strong deoxidizing agent such as Al, Mg, Zr and Ti are contained and these refractory oxides are incorporated into the slag composition to form a welded structure. Corresponding to expansion of target leg length and construction welding condition range of objects, Ni, Cr, Mo, Nb, V, B
To improve various properties (strength, toughness, fire resistance, heat resistance, weather resistance, etc.) of the weld metal that meet the required quality of the applied steel by including alloying agents such as Bi, Bi ₂ O ₃ etc. It is also possible to include a slag peeling aid within a range that does not impair the effects of the present invention.

The steel shell is preferably a mild steel material generally used for flux-cored wires from the viewpoint of drawability after flux filling, but in addition to C, Si and Mn, the above deoxidizing agent and alloying agent. It is also possible to use a component system containing.

The flux filling rate is set to 8% or more in order to obtain high welding and high efficiency. On the other hand, the upper limit of the flux filling rate is 30% in consideration of the fact that if the filling rate is too high, wire breakage is likely to occur. And Regarding the wire cross-sectional shape, as shown in FIGS. 2 (a), (b), and (c),
A general shape in which the outer skin 7 is filled with the flux 8 may be used, but a seamless type (a) in which the outer skin has no opening
Does not absorb the filled flux even in the environment of use such as at the seaside or in the rainy season, and the primer resistance does not deteriorate.

A fine wire having a nominal outer diameter of 1.0 to 2.0 mm is preferable in terms of high welding and high efficiency. Also,
Applying Cu plating to the wire surface improves the electrical conductivity and rust resistance during welding.

The shield gas used when the flux-cored wire of the present invention is used is inexpensive CO ₂ gas, Ar gas or Ar-CO which can reduce fumes and spatter.
₂ Mixed gas can be used. Hereinafter, the effects of the present invention will be described in more detail with reference to Examples.

[0027]

EXAMPLES Mild steel pipe (C: 0.05%, Si: 0.0
3%, Mn: 0.35%, P: 0. P: 0.013%,
(S: 0.005%) was used as the outer skin material, and after the flux was filled, wire drawing (intermediate annealing for softening and lowering the hydrogenation of the outer skin was carried out once, and the temperature and Hold time), flux filling rate 15%, wire diameter 1.2
mm seamless type flux cored wire was prototyped. Table 1 shows the flux components of the prototype wire.

Using these trial wires, a horizontal fillet welding test was conducted by assembling the test body shown in FIG. In FIG. 3, 9 steel plates (steel type SM490B) coated with a primer are used, the lower plate 2 has a plate thickness of 16 mm, and the vertical plate 1 has a plate thickness of 12
mm, the test body length was 2 m, and the primer film thickness was about 25 μm. Reference numeral 3 denotes a welded first pass side bead, 3'denotes a welded second pass side bead, and further shows a pit 10 and a gas groove 11 of a welding defect.

Table 2 shows welding conditions (automatic welding), and Table 3 shows welding test results. The welding sequence was such that after the end of the first pass, the second pass was welded. First evaluation of primer resistance
No pits or gas grooves occurred on the pass side, so the second
I went on the pass side.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

Test No. Nos. 1 to 21 are test results with wash primer-coated steel sheets. Test No. 1 to 6 are cases where the flux-cored wires (W1 to 6) according to the present invention are used, and uneven solidification of the molten slag is effectively formed,
No pits or gas grooves are generated. In addition, a bead shape with good conformability at the bead toe was obtained, and slag was easily removed. The test No. 20 and 21 are flux-cored wires (W20,
21), the welding speed could be increased. On the other hand, the test No. 7 to 19 are comparative examples.

In the comparative example, the test No. No. 7 (W7) lacks TiO ₂ , and the test No. 8 (W8) has an excessive amount of TiO ₂ , and the test No. 9 (W9) lacks SiO ₂ , test N
o. No. 10 (W10) has excessive SiO ₂ , and test No. 11
(W11) does not contain ZrO ₂ , test No.
No. 12 (W12) has excess ZrO ₂ , and test No. 13 (W
13) is insufficient in iron oxide, and the test No. No. 14 (W14) has an excessive iron oxide, and the test No. Test No. 15 (W15) does not contain Ca, Test No. 16 (W16) has excessive Ca, and the test No. In 18 (W18), since F was excessive, uneven solidification of the molten slag was not appropriately formed, and pits and gas grooves were generated. Further, the bead shape and appearance were inferior, and it was difficult to remove slag.

Test No. Since No. 17 (W17) did not contain F, the formation of pits and gas grooves and the bead shape were inferior. Test No. In No. 19 (W19), since the total hydrogen content of the wire was too large, pits and gas grooves were generated. Test No.
Nos. 22 to 24 are test results obtained by using an inorganic zinc primer-coated steel sheet. Test No. 22 and 23 are the cases where the flux-cored wire (W1, 6) according to the present invention is used, uneven solidification of molten slag is effectively formed, pits and gas grooves are not generated, and bead shape and slag removal are also good. Met. Test No. 24 is a comparative example, and C is attached to the wire (W15).
Since "a" was not contained, pits were generated when the welding speed increased even for the inorganic zinc primer coated steel sheet.

[0036]

As described above, according to the flux-cored wire for gas shielded arc welding of the present invention, it is possible to improve the primer resistance, which is a problem in fillet welding of a primer-coated steel sheet, and thereby the bead shape and slag can be improved. The removability is also good, and the welding efficiency can be improved and the quality of the welded part can be improved.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining a horizontal fillet welding situation (solidification unevenness of molten slag) according to the present invention,
(A) is a bead plane, (b) is a BB cross section, (c) is C
-C cross section is shown.

2 (a), (b) and (c) are schematic diagrams showing cross-sectional shapes of various flux-cored wires.

FIG. 3 is a schematic view showing a horizontal fillet welded test body and a cross section after welding in Examples.

[Explanation of symbols]

1: Standing plate 2: Lower plate 3: Bead 4: Slag 5: Thin part of slag encapsulation 6: Thick slag encapsulation 7: outer skin 8: Flux 9: Primer 10: Pit 11: Gas groove

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-9-239597 (JP, A) JP-A-7-328795 (JP, A) JP-A-7-314181 (JP, A) JP-A-3- 294092 (JP, A) JP-A 1-262096 (JP, A) JP-A 61-206597 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B23K 35/368

Claims (2)

(57) [Claims] 1. A flux-cored wire for gas shielded arc welding, comprising a steel shell filled with flux, wherein the weight% of the total weight of the wire is TiO ₂ : 2.0 to 5.0%, SiO ₂ : 0. _{2 to} 0.6%, ZrO ₂ : 0.2 to 0.8%, iron oxide: 1.0 to 3.5%, Ca: 0.03 to 0.30%, and F: 0. A flux-cored wire for gas shield arc welding, which is resistant to primer and is characterized by containing 005 to 0.05%. 2. The flux-cored wire for primer-resistant gas shielded arc welding according to claim 1, wherein the total hydrogen content of the wire is 20 ppm or less.