KR20120131453A - Gas shielded arc welding titania based flux cored wire having excellent crack resistance - Google Patents

Abstract

PURPOSE: A titania based flux cored wire for gas-shielded arc welding is provided to obtain excellent crack resistance and lower-temperature impact toughness by controlling components and the correlation of the components as well. CONSTITUTION: A titania based flux cored wire for gas-shielded arc welding with excellent crack resistance comprises 4-9weight% of TiO2, 0.01-0.07 weight% of C, 1.0-3.0weight% of Mn, 0.1-1.0weight% of Ni, 0.1-1.0weight% of Mg, 0.01-0.1weight% of F, 0.002-0.007weight% of B, 2.0-6.0 weight% of Fe, 0.03weight% or less of Nb, 0.04 weight% or less of V, 0.2-1.0weight% of Na, and the remaining amount of Fe in a metal outer sheath and inevitable impurities. [Reference numerals] (AA) -40°C Impact toughness(J); (BB) Embodiment; (CC) Comparison case

Description

Titania-based flux filling wire for gas shield arc welding with excellent crack resistance {GAS SHIELDED ARC WELDING TITANIA BASED FLUX CORED WIRE HAVING EXCELLENT CRACK RESISTANCE}

The present invention relates to a flux filling wire for welding, and more particularly, to a titania-based flux filling wire for gas shielded arc welding excellent in low-temperature impact toughness and crack resistance of a weld metal.

In recent years, various materials such as ships, steel structures, offshore plants, chemical facilities, and storage facilities require steel materials with high strength and functionality, and thus welding materials must also select functional materials accordingly. In particular, in thick plate welding, impact toughness and crack resistance may become weak due to various parameters depending on welding conditions and welding techniques of high heat input. In addition, the general titania-type flux-filled wire is excellent in the electron-weld weldability due to the oxide, but it is difficult to secure relatively low-temperature impact toughness.

In order to solve the above problem, Japanese Patent Laid-Open No. 58-16796 discloses a Titania-based flux-filled wire for gas shield arc welding, in terms of weight% of the wire, TiO ₂ : 4 to 8.5%, Mg: 0.2 to 0.8%, and Ti. : 0.03 ~ 0.7%, B: 0.002 ~ 0.025%, Mn: 1.0 ~ 3.0%, Si: 0.1 ~ 1.2%, In addition, it provides a weld metal impact toughness at low temperature by providing flux consisting of metal fluoride and oxide. have.

However, the boron (B) added in the patent can ensure the impact toughness of the weld metal, but may also act as a cause of high-temperature cracking due to the grain boundary segregation, which is insufficient in terms of improving crack resistance.

In addition, Korean Patent Laid-Open Publication No. 2002-0008681 proposes to secure good low-temperature impact toughness and to improve welding workability by controlling the ratio of titanium oxide and non-titanium oxide, but it has been somewhat insufficient in terms of crack resistance.

Therefore, the inventors of the present invention have disclosed and disclosed a flux-filled wire which is excellent in the electric field welding workability and excellent in the weld metal low-temperature impact toughness and crack resistance through continuous research.

One aspect of the present invention is to provide a titania-based flux-filled wire for gas shield arc welding that can ensure crack resistance and low temperature impact toughness while maintaining good welding workability.

The present invention provides a flux-filled wire in which a flux is filled in a metal shell, in terms of weight% of the total weight of the wire, TiO ₂ : 4 to 9%, C: 0.01 to 0.07%, Si: 0.2 to 0.6%, and Mn: 1.0 -3.0%, Ni: 0.1-1.0%, Mg: 0.1-1.0%, F: 0.01-0.1%, B: 0.002-0.007%, Iron: 2.0-6.0%, Nb: 0.03% or less, V: 0.04% or less , Na: 0.2-1.0%, containing Fe and inevitable impurities in the remaining metal shell,

The present invention provides a titania-based flux-filled wire for gas-shielded arc welding having excellent crack resistance of the relation (C * B * 10 ⁴ ) ² + (Si ³ * 10) of 1.5 to 6.0.

According to the present invention, by controlling the compositional components of the flux-filled wires and controlling their component relationships, it is possible to provide a titania-based flux-filled wire for gas shielded arc welding having excellent crack resistance and low temperature impact toughness. .

Figure 1 shows the side cross-section (a) and the plane (b) of the high temperature crack generation test base material of the embodiment.
Figure 2 is a graph showing the -40 ℃ low temperature impact toughness value for the value of (C * B * 10 ⁴ ) ² + (Si ³ * 10).

Hereinafter, the present invention will be described in detail.

The composition of the flux filling wire of the present invention will be described in detail. The following composition is weight percent (hereinafter%) with respect to the total weight of the wire.

It is preferable to make content of carbon (C) into 0.01 to 0.07%. If the C content is less than 0.01%, the toughness and tensile properties of the deposited metal deteriorate. If the content of C is greater than 0.07%, pearlite is promoted. Since there also exists a problem that a large amount of spatters generate | occur | produce also in workability, it is preferable to make C content into 0.01 to 0.07%.

The content of TiO ₂ is preferably 4-9%. If the content of TiO ₂ is less than 4%, the amount of slag is insufficient, so that molten metal cannot be sufficiently protected from the atmosphere, and slag solidification is slowed during the electron beam welding, thereby degrading weldability. In addition, when the content of TiO ₂ exceeds 9%, it is not preferable because not only slag formation is excessive and meltability and fluidity are deteriorated, but also a part of the slag may be mixed into the weld metal to degrade the mechanical performance of the weld. not.

The content of manganese (Mn) is preferably 1.0 to 3.0%. The Mn reacts with S as a relatively weak deoxidizer and forms MnS before FeS, thereby preventing the formation of a low melting point compound due to segregation of S. When the Mn content is less than 1.0%, the strength of the weld metal is lowered, coarsening of the weld metal is promoted due to lack of hardenability, and deterioration at low temperature toughness can be brought about. In addition, when the content exceeds 3.0%, the meltability is lowered, slag solidification is slowed, the appearance of the bead may worsen, there is a fear of high temperature crack generation.

Sodium (Na) is an arc stabilizer, which stabilizes the arc during welding and is a component showing good workability. The Na content is preferably 0.2 to 1.0%. If the content of Na is less than 0.2%, there are phenomena such as arc anxiety and an increase in spatter. If the content of Na exceeds 1.0%, there is a problem that the arc concentration is increased, the arc size is decreased, and the arc anxiety is caused. It is preferable to set it as 1.0%.

The content of nickel (Ni) is preferably made 0.1 to 1.0%. Ni is an element capable of lowering the transition temperature of weld metal impact toughness and stabilizing low temperature impact toughness. If the content of Ni is less than 0.1%, the above-mentioned predetermined effect cannot be exhibited. If the content of Ni is more than 1.0%, the hardenability is excessively increased to lower the toughness of the weld heat affected zone and the high temperature cracking of the weld heat affected zone and the weld metal. Since there is a possibility of occurrence, it is preferable to make the content 0.1 to 1.0%.

The content of magnesium (Mg) is preferably 0.1 to 1.0%. The Mg is a strong deoxidizing agent that reacts with oxygen in the molten metal to suppress the formation of non-metallic inclusions, thereby improving the cleanliness of the weld metal. If the content of Mg is less than 0.1%, it is difficult to expect the above-described predetermined effects. If the content of Mg is more than 1.0%, the amount of welding fume and spatter is increased, and the slag foreskin is deteriorated, so that the content is 0.1 to 1.0%. desirable.

It is preferable to make content of fluorine (F) into 0.01 to 0.1%. The F is added in the form of a metal fluorine compound, and this F serves to improve the arc stability and to suppress the occurrence of defects. If the content of F is less than 0.01%, the above-mentioned role is insignificant, and if it exceeds 0.1%, the amount of fume is increased and the weldability is also lowered. Therefore, the content is preferably 0.01 to 0.1%.

The content of iron is preferably 2.0 to 6.0%. The iron increases the amount of weld metal in welding and combines with oxygen to form an oxide. If the iron content is less than 2.0%, the amount of weld metal is insufficient, and it may cause arc anxiety and slag flow deterioration. If the content of iron is more than 6.0%, excessive occurrence of fume and spatter and slag peelability may be reduced, so that the content is 2.0. It is preferable to set it as -6.0%.

Niobium (Nb) 0.03% or less and vanadium (V) 0.04% or less are preferably added. The Nb and V are elements added as impurities, and not only increase the strength of the welded portion by precipitation at the grain boundary, but also increase the hardness, but when excessively included, it reduces the toughness of the weld metal, so that the content It is preferable to set it as 0.03% or less and 0.04% or less, respectively.

The content of boron (B) is preferably set to 0.002 to 0.007%. B serves to increase the strength and toughness of the weld by forming BN to suppress the formation of grain boundary ferrite and to refine the structure. If the content of B is less than 0.002%, it is difficult to expect the role, and if it exceeds 0.007%, boride is formed into a continuous network to reduce impact value due to hardening, not only to deteriorate toughness but also to lower meltability. And the content thereof is preferably 0.002% to 0.007% because of the possibility of cracking.

The content of silicon (Si) is preferably made 0.2 to 0.6%. The Si serves to maintain the strength of the weld metal and improve slag fluidity and bead shape. If the content of Si is less than 0.2%, there is a problem in that tensile strength and impact toughness of the weld metal are lowered, and slag flow and bead appearance are lowered. If the content exceeds 0.6%, the transformation of the phase martensite in the weld metal (MA constituent) is promoted to lower the low-temperature impact toughness and there is a fear of cracking. That is, by forming a Fe-S-Si-O compound to promote high-temperature cracking, it can reduce the low-temperature impact toughness due to such a compound.

In addition to the above composition, the rest includes Fe and inevitable impurities in the metal shell. However, this does not exclude the addition of other compositions.

In the flux-filled wire of the present invention, it is preferable that the relationship between the contents of C, B, and Si in the composition, and the value of (C * B * 10 ⁴ ) ² + (Si ³ * 10) satisfy 1.5 to 6.0. Although the content of C and B is not high, it is a component that greatly affects impact toughness and crack resistance, and Si also contributes to improvement of impact toughness, but if the content is large, crack resistance is deteriorated. The present inventors, focusing on this point, and evaluated the impact toughness and crack resistance according to the change in the content of C, B and Si, as a result, (C * B * 10 ⁴ ) ² + (Si ³ * 10) When the value of satisfies 1.5 ~ 6.0 is to confirm the stable impact toughness and crack resistance can be secured at the same time to propose the present invention. When the value is out of the above range, it is difficult to secure stable impact toughness and crack resistance at the same time.

Hereinafter, embodiments of the present invention will be described in detail. The following examples are provided for the understanding of the present invention, and the present invention is not limited thereto.

(Example)

To prepare a flux filling wire that satisfies the composition of Table 1. The flux filling wire is a titania-based flux filling wire in which a metal shell is filled with a flux of 10 to 20% with a flux of 1.2 mm in diameter. On the other hand, the metal shell was used as a mild steel containing C: 0.02%, Si: 0.002%, Mn: 0.2%, P: 0.02%, S: 0.009%. The remainder in Table 1 below is Fe and inevitable impurities in the skin.

The flux-filled wire was used to weld ASTM E36 steel, and the impact toughness and tensile strength were measured according to AWS A5.20, and the results are shown in Table 2. At this time, the case of yield strength of 390 MPa or more, tensile strength of 490-670 MPa, elongation of 22% or more, and impact toughness of 47 J or more at -40 ° C was evaluated as pass. For the results of Table 2, a graph of the low temperature impact toughness value with respect to the value of (C * B * 10 ⁴ ) ² + (Si ³ * 10) is shown in FIG.

On the other hand, the high temperature crack generation test for the evaluation of the crack resistance was prepared by the EH36 base material having a thickness of 25mm, 500mm in length as shown in Figure 1 and subjected to the first layer welding under high heat input welding conditions (250A / 32V). It was shown in Table 4 by measuring the degree of high temperature crack generation according to. Figure 1 (a) shows a side cross-section of the base material, Figure 1 (b) shows a plane.

In the present embodiment, first, the first crack welding on the surface of the weld bead is performed using the ceramic backing agent as shown in Table 1 using the welding conditions shown in Table 3 as a high temperature crack generation determination method. It was calculated as a percentage of the total weld length (500 mm).

Further, in order to confirm the occurrence of low temperature cracks, the superficial cracks were subjected to gouging and re-welded, and the welding was completed by 5 Layer 7 Pass. Then, 72 hours after welding, a nondestructive test was carried out to check for cracks.

division C Si Mn B Ni Mg TiO ₂ F Na Nb V iron content (C * B * 10 ⁴ ) ² + (Si ³ * 10) Inventory 1 0.031 0.48 2.2 0.0028 0.35 0.45 6.45 0.078 0.58 0.012 0.023 3.05 1.86 Inventive Example 2 0.043 0.45 2.4 0.0033 0.38 0.48 6.58 0.023 0.44 0.015 0.024 4.28 2.92 Inventory 3 0.029 0.47 2.1 0.0032 0.35 0.44 7.25 0.083 0.58 0.013 0.019 4.12 1.90 Honorable 4 0.031 0.58 2.3 0.0027 0.45 0.40 5.88 0.098 0.74 0.009 0.025 3.65 2.65 Inventory 5 0.038 0.21 2.5 0.0034 0.48 0.42 4.99 0.042 0.81 0.012 0.024 4.02 1.76 Inventory 6 0.042 0.24 2.7 0.0029 0.50 0.49 6.15 0.084 0.52 0.009 0.019 3.88 1.62 Honorable 7 0.041 0.36 2.3 0.0041 0.57 0.50 7.32 0.026 0.57 0.016 0.024 3.75 3.29 Inventive Example 8 0.051 0.38 2.4 0.0043 0.80 0.38 6.87 0.095 0.68 0.012 0.023 3.94 5.36 Comparative Example 1 0.018 0.35 2.2 0.0029 0.45 0.40 8.15 0.066 0.61 0.014 0.021 4.01 0.70 Comparative Example 2 0.031 0.21 2.6 0.0020 0.42 0.41 7.85 0.071 0.58 0.013 0.024 4.08 0.48 Comparative Example 3 0.068 0.35 2.1 0.0051 0.39 0.54 6.32 0.058 0.34 0.011 0.021 4.38 12.46 Comparative Example 4 0.042 0.58 2.8 0.0069 0.47 0.38 6.11 0.042 0.65 0.014 0.032 5.25 10.35 Comparative Example 5 0.130 0.42 2.3 0.0025 0.31 0.44 5.85 0.068 0.74 0.011 0.022 4.55 11.30 Comparative Example 6 0.032 0.45 2.2 0.0009 0.43 0.48 5.97 0.085 0.80 0.009 0.019 4.32 0.99 Comparative Example 7 0.031 0.40 2.6 0.0122 0.38 0.47 6.88 0.048 0.84 0.008 0.024 3.98 14.94 Comparative Example 8 0.019 0.18 2.4 0.0033 0.33 0.50 5.81 0.056 0.81 0.014 0.021 4.25 0.45 Comparative Example 9 0.030 0.20 3.0 0.0018 0.75 0.43 7.12 0.021 0.85 0.009 0.020 3.86 0.37 Comparative Example 10 0.029 0.84 2.9 0.0028 0.80 0.51 8.08 0.094 0.45 0.013 0.021 4.15 6.59 Comparative Example 11 0.090 0.83 2.5 0.0013 0.42 0.48 7.45 0.019 0.56 0.014 0.023 3.25 7.09 Comparative Example 12 0.033 1.1 2.4 0.0035 0.39 0.37 6.55 0.071 0.31 0.011 0.019 4.22 14.64

division
Tensile Strength (MPa)
Impact toughness evaluation
-30 ℃ -40 ° C Inventory 1 601 105 61 pass Inventive Example 2 611 122 85 pass Inventory 3 603 118 82 pass Honorable 4 625 92 63 pass Inventory 5 598 135 108 pass Inventory 6 615 121 102 pass Honorable 7 624 152 113 pass Inventive Example 8 620 155 128 pass Comparative Example 1 580 78 35 fail Comparative Example 2 558 38 18 fail Comparative Example 3 604 164 115 pass Comparative Example 4 620 105 55 pass Comparative Example 5 645 95 43 fail Comparative Example 6 635 78 29 fail Comparative Example 7 620 182 158 pass Comparative Example 8 565 85 36 fail Comparative Example 9 578 51 17 fail Comparative Example 10 630 65 25 fail Comparative Example 11 642 48 18 fail Comparative Example 12 660 105 73 pass

Protective gas and flow rate polarity Welding position Welding current / voltage Welding speed Etc 100% CO ₂
20 ~ 25ℓ / min DC reverse polarity
(DC +) Downward (1G) 250 A / 32 V 18 (cm / min) Improvement angle: 34 °
Root Gap: 5mm
Stick Out: 20-25mm
Welding method: Retraction

division Whether high temperature crack occurs High Temperature Cracking Rate (%) Low temperature crack evaluation Inventory 1 radish - radish pass Inventive Example 2 radish - radish pass Inventory 3 radish - radish pass Honorable 4 radish - radish pass Inventory 5 radish - radish pass Inventory 6 radish - radish pass Honorable 7 radish - radish pass Inventive Example 8 radish - radish pass Comparative Example 1 radish - radish pass Comparative Example 2 radish - radish pass Comparative Example 3 U 32 U fail Comparative Example 4 U 41 U fail Comparative Example 5 U 76 U fail Comparative Example 6 radish - radish pass Comparative Example 7 U 39 U fail Comparative Example 8 radish - radish pass Comparative Example 9 radish - radish pass Comparative Example 10 U 12 U fail Comparative Example 11 U 62 U fail Comparative Example 12 U 58 U fail

As shown in FIG. 2, Tables 2 and 4, it was confirmed that the flux filling wire of the composition of the invention Examples 1 to 8 satisfying the scope of the present invention is excellent in both low-temperature impact toughness and crack resistance.

However, in Comparative Examples 1 to 4, the component range is included in the scope of the present invention, while Comparative Examples 1 and 2 are less than the value of (C * B * 10 ⁴ ) ² + (Si ³ * 10) in the range of the present invention. The comparative examples 3 and 4 exceed the range of this invention. At this time, Comparative Examples 1 and 2 were not satisfactory low-temperature impact toughness, Comparative Examples 3 and 4 it was confirmed that the crack occurs at high and low temperatures.

Comparative Example 5 is the case where the content of C is outside the scope of the present invention, the value of (C * B * 10 ⁴ ) ² + (Si ³ * 10) is outside the scope of the present invention, the low-temperature impact toughness is not satisfactory, cracks It was confirmed that this occurred. In Comparative Examples 6, 8 and 9, the content of B or Si is less than the present invention, and the value of (C * B * 10 ⁴ ) ² + (Si ³ * 10) is outside the scope of the present invention, and thus the low temperature impact Toughness was found to be inferior. On the other hand, Comparative Example 7 is the case where the content of B exceeds the range of the present invention, the value of (C * B * 10 ⁴ ) ² + (Si ³ * 10) is outside the scope of the present invention, hot crack and cold crack It was confirmed that this occurred. Comparative Examples 10 to 12, the content of at least one of C, Si, B is outside the scope of the present invention, the value of (C * B * 10 ⁴ ) ² + (Si ³ * 10) exceeds the scope of the present invention As a comparative example, Comparative Examples 10 and 11 were not satisfactory for both low-temperature impact toughness and crack resistance, and Comparative Example 12 was confirmed that high temperature and low temperature cracking occurred. Thus, it can be seen that the flux-filled wire outside the scope of the present invention cannot be suitably used for the first layer welding of thick plates.

Claims (1)

Flux-filled wire in which the flux is filled in the metal shell, in terms of weight% of the total weight of the wire, TiO ₂ : 4-9%, C: 0.01-0.07%, Si: 0.2-0.6%, Mn: 1.0-3.0% , Ni: 0.1-1.0%, Mg: 0.1-1.0%, F: 0.01-0.1%, B: 0.002-0.007%, Iron: 2.0-6.0%, Nb: 0.03% or less, V: 0.04% or less, Na: 0.2-1.0%, containing Fe and unavoidable impurities in the remaining metal shell,
Titania-based flux-filled wire for gas-shielded arc welding with excellent crack resistance of the relation (C * B * 10 ⁴ ) ² + (Si ³ * 10) of 1.5 to 6.0.

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