KR20100059269A - Flux cored wire for gas shielded arc welding of high tensile strength steel - Google Patents

Abstract

PURPOSE: A flux cored wire for gas-shielded arc welding for high tensile strength steel is provided to improve the ductility of a welding part by adding silicon to a steel outer cover and flux and improving the movement of the slag and the outer shape of bead. CONSTITUTION: A flux cored wire for gas-shielded arc welding for high tensile strength steel consists of C 0.03~0.11 weight%, TiO2 3.0~10 weight%, Mn 1.0~4.5 weight%, Si 0.3~2.0 weight%, B 0.002~0.04 weight%, Ni 0.5~3.5 weight%, Mg 0.1~1.5 weight%, Al 0.01~0.8 weight%, one or more kinds 0.1~1.2 weight% selected among Cr, Mo, and V, and the rest consisting of Fe and impurities.

Description

Flux-filled wire for gas shielded arc welding for high-strength steel {FLUX CORED WIRE FOR GAS SHIELDED ARC WELDING OF HIGH TENSILE STRENGTH STEEL}

The present invention relates to a flux-filled wire used for welding high tensile strength steel of tensile strength of 620 MPa or more, and more particularly, a flux-filled wire for gas shielded arc welding for high-strength steel having excellent cryogenic impact toughness and crack resistance and excellent welding workability. It is about.

In recent years, the trend of large-sized structures in shipbuilding, offshore structures, and steel frames continues, and lightweight structures have been promoted for the purpose of cost reduction and safety improvement. Therefore, the strength of steels used is rapidly increasing. However, the development of the welding material corresponding to this, that is, the flux filling wire for high strength steel welding, which is excellent in the electric field welding workability and cryogenic impact toughness, and secures the crack resistance, is still slow.

The related technologies are as follows. Japanese Unexamined Patent Publication No. 3-47695 proposes to improve welding workability and impact toughness by controlling the content of TiO ₂ , MnO, MgO and the ratio of TiO ₂ / MgO, but the cryogenic impact toughness at -60 ℃ There is a difficult problem to secure. In addition, Japanese Patent Application Laid-open No. Hei 8-174275 proposes to improve the impact toughness and work efficiency by regulating the content of C, Si, Mn, P, S, Ni, etc. and adding an appropriate amount of Ta, but a good electronic tax There were some limitations in securing weldability.

Therefore, in order to meet the expectations of the industrial site, development of flux-filled wire excellent in cryogenic impact toughness and crack resistance and excellent in electric field welding work is required for high strength steel welding of tensile strength of 620 MPa or more.

The present invention provides a gas shielded arc welding flux-filled wire for high-strength steel that is excellent in cryogenic impact toughness and crack resistance of a weld metal obtained after welding of high-strength steel, and excellent in electric field welding workability.

The present invention provides a flux-filled wire in which a flux is filled in a steel shell, wherein the weight is based on the total weight of the wire, C: 0.03 to 0.11%, TiO ₂ : 3.0 to 10%, Mn: 1.0 to 4.5%, and Si. : 0.3 to 2.0%, B: 0.002 to 0.04%, Ni: 0.5 to 3.5%, Mg: 0.1 to 1.5%, Al: 0.01 to 0.8%, at least one selected from the group consisting of Cr, Mo and V is 0.1 to 1.2%, the remainder is made of Fe in the steel shell, iron in the flux and unavoidable impurities, provides a flux filling wire for gas shielded arc welding for high-strength steel, characterized in that the following formula F value satisfies 110 ~ 210. .

As described above, the present invention provides a gas shielded arc welding flux filling wire for high-strength steel, which is excellent in cryogenic impact toughness and crack resistance of weld metal, and also excellent in electric field welding workability.

Hereinafter, the present invention will be described in detail.

The present inventors have conducted research and efforts for the development of a gas shielded arc welding wire suitable for welding high tensile steel with a tensile strength of 620 MPa or more, and control the content of C, Mn, B, Ni, etc. contained in the wire, respectively. Flux filling wire for gas shielded arc welding for high-strength steel with excellent cryogenic impact toughness and crack resistance and excellent electric field welding workability by specifying the ratio of the components to the cryogenic impact toughness and crack resistance and its ratio. By developing the present invention was proposed.

Hereinafter, the component of the present invention will be described in detail (hereinafter,% by weight).

Carbon (C) is included in the steel shell and the filled flux of the flux-filled wire of the present invention to maintain the tensile strength of the weld metal and the oxidation inclusions (MnS, Al ₂ O ₃ , SiO _2, etc.) penetrate into the weld metal. It is suppressed to form a healthy weld part. In the present invention, it is preferable to limit the content of C to 0.03 ~ 0.11%. If the content is less than 0.03%, the impact toughness and tensile strength of the weld metal deteriorate, whereas if it exceeds 0.11%, the tensile strength is excessively high and the high temperature cracking resistance is lowered.

TiO ₂ is a major slag forming agent that protects the molten pool from the atmosphere during the welding process and forms a weld metal. In the present invention, the content of TiO ₂ is preferably limited to 3.0 to 10%. If the content is less than 3.0%, the arc is unstable and the amount of slag is insufficient to sufficiently protect the weld metal from the atmosphere. If the content is more than 10%, the slag formation is excessive and fluidity is deteriorated. This is because the mechanical properties of the welded portion are reduced due to mixing therein.

Manganese (Mn) is included in the flux filled with the steel jacket of the flux-filled wire of the present invention as a deoxidizing agent, thereby reducing the amount of oxygen in the weld metal, maintaining the strength of the weld metal, and also improving the appearance of the beads and stabilizing austenite. As a component, the fall of impact toughness at cryogenic temperatures is prevented. In the present invention, it is preferable to limit the content of Mn to 1.0 ~ 4.5%. If the content is less than 1.0%, the effect of improving the appearance of the beads is insufficient, and the tensile strength and impact toughness of the weld metal are deteriorated. If the content is more than 4.5%, the arc is unstable, the meltability is deteriorated, and high temperature cracking may occur. .

Silicon (Si) is included in the flux that is filled with the steel shell of the flux-filled wire of the present invention as a deoxidizer, thereby reducing the amount of oxygen in the weld metal, maintaining the strength of the weld metal, and improving the appearance of beads and fluidity of the slag. In addition, the ferrite stabilizing component serves to improve the ductility of the weld. In the present invention, the content is preferably limited to 0.3 to 2.0%, but if the content is less than 0.3%, the effect of addition cannot be obtained. If the content exceeds 2.0%, the arc may become unstable and the impact toughness may be lowered. .

Boron (B) forms a BN during welding, and serves to improve the tensile strength and impact toughness of the weld by miniaturizing the structure by inhibiting the formation of grain boundary ferrite. In the present invention, it is preferable to limit the content of B to 0.002 ~ 0.04%, because it does not exhibit a predetermined effect at less than 0.002%, because if the content exceeds 0.04% high temperature cracks are likely to occur.

Nickel (Ni) is an austenite stabilizing component and an effective component for stabilizing impact toughness at cryogenic temperatures. In the present invention, it is preferably added 0.5 to 3.5%. This is because if the content is less than 0.5%, the effect of the addition cannot be exhibited, and if the content is more than 3.5%, the strength of the weld metal may be excessively increased and may cause arc anxiety and cracking.

Chromium (Cr), molybdenum (Mo) and vanadium (V) are components that contribute to maintaining the appropriate strength of the welded part and improving impact toughness. In the present invention, at least one selected from the group consisting of Cr, Mo and V is 0.1 to 1.2. It is preferable to add%. If the content is less than 0.1%, a predetermined effect is not seen, and if the content is more than 1.2%, there is a fear of causing a decrease in impact toughness and cracking.

Magnesium (Mg) is a strong deoxidizer that reduces the amount of oxygen in the weld metal and improves arc stability and concentration. In the present invention, the content is preferably limited to 0.1 to 1.5%. If the content is less than 0.1%, the impact toughness may be reduced due to deoxidation shortage. If the content exceeds 1.5%, the arc becomes unstable and spatter generation occurs. There is a risk of cracking by causing hardening of the weld.

Aluminum (Al) is a strong deoxidizer, which reduces the amount of oxygen in the weld metal, improves arc stability and concentration, and improves the ductility of the weld as a ferrite stabilizing component, thereby improving crack resistance. In the present invention, it is preferable to limit the content to 0.01 to 0.8%, but less than 0.01% can not see the effect of the addition, if it exceeds 0.8% the arc may be unstable and impact toughness may be reduced.

The flux filling wire of the present invention contains, in addition to the above components, Fe in the steel shell, iron in the flux, and unavoidable impurities.

In the present invention, in order to secure good cryogenic impact toughness and excellent crack resistance, the ratio between the component for improving the impact toughness and the component for increasing the ductility of the weld portion to improve the crack resistance is appropriately controlled in an appropriate range.

In other words, considering the degree of contribution to the austenite stabilization and the impact on the cryogenic impact toughness of each component, the index is given to Ni, Mn, B, respectively, in consideration of the degree of contribution to the ferrite stabilization and the contribution to the weld ductility A proper index was given to Si and Al. Next, considering the ratio of the ferrite stabilizing component to the austenite stabilizing component, the following formula F value was obtained, and the range was set based on the experimental results.

In the present invention, the F value is preferably satisfying 110 ~ 210. When the F value is in the range of 110 to 210, the cryogenic impact toughness and crack resistance are excellent, but when the value is less than 110, the cryogenic impact toughness is insufficient, and when it exceeds 210, the impact toughness is good but the crack resistance is good. There is a disadvantage of deterioration.

The correlation between the F value and the impact toughness and crack initiation at −60 ° C. is shown in FIG. 1. Referring to FIG. 1, when the F value is 110 to 210, a weld metal having excellent cryogenic impact toughness and crack resistance may be obtained.

The high-strength steel gas shielded arc welding flux filling wire of the present invention can be used as a protective gas in any of CO ₂ gas or a mixed gas of Ar and CO ₂ .

Hereinafter, embodiments of the present invention will be described in detail.

(Example)

The flux filling wires for gas shield arc welding having a diameter of 1.2 mm having the composition of Table 1 were prepared, respectively, and the composition of the steel shell used was shown in Table 2 as a weight% with respect to the total weight of the shell.

Each wire prepared as described above was welded to the HT780 class base metal under the welding conditions shown in Table 3 (V type butt welding) to evaluate the crack resistance, tensile strength and impact toughness of the weld metal. It is shown in Table 4 to evaluate the electron fine welding workability.

Cracking was evaluated by non-destructive test after 168 hours after welding. Tensile strength was higher than 620N / mm2 and impact toughness was better than 47 Joule at -60 ℃. And, weldability was measured through the sensory evaluation of the welder. However, in Table 4, (circle) is excellent, (circle) is good, (triangle | delta) is normal, and x represents a defect.

division TiO ₂ C Mn Si Ni B Cr Mo V Cr + Mo + V Mg Al F value Inventive Example 1 5.1 0.05 1.5 0.4 0.6 0.008 0.1 0.1 0.2 0.15 0.02 138 Inventive Example 2 5.5 0.07 2.5 0.7 3.4 0.035 0.1 0.1 0.5 0.02 175 Inventive Example 3 9 0.11 4.5 2 2.9 0.002 0.1 0.1 0.8 0.40 112 Inventive Example 4 9 0.05 4 0.35 3.5 0.035 1.2 1.2 0.8 0.2 191 Inventive Example 5 5.5 0.07 1.1 0.6 3.4 0.04 0.5 0.5 1.4 0.8 129 Inventive Example 6 3.5 0.06 1.3 One 3.2 0.038 0.2 0.5 0.3 1.0 1.3 0.3 147 Inventive Example 7 7.8 0.08 3.8 0.5 3.2 0.035 0.5 0.5 0.65 0.01 200 Inventive Example 8 9.5 0.04 3.8 0.65 2.9 0.018 0.3 0.2 0.5 0.4 0.05 170 Inventive Example 9 5.6 0.03 4.2 0.8 2.5 0.015 0.3 0.6 0.9 0.6 0.65 127 Inventive Example 10 4.2 0.04 4.3 0.32 2.5 0.008 0.4 0.4 0.8 0.01 210 Inventive Example 11 6.8 0.05 1.9 1.1 1.7 0.017 0.4 0.2 0.6 0.9 0.45 110 Inventive Example 12 6.3 0.08 2.3 0.35 2.2 0.009 0.5 0.1 0.6 0.7 0.02 184 Comparative Example 1 4.5 0.04 0.8 0.8 3.4 0.03 0.1 0.2 0.3 0.3 0.1 151 Comparative Example 2 9 0.06 1.2 2.3 3.5 0.006 0.5 0.2 0.1 0.8 0.3 0.5 100 Comparative Example 3 3.5 0.09 2.5 1.8 0.3 0.02 0.2 0.1 0.2 0.5 One 0.69 86 Comparative Example 4 5.8 0.11 1.5 0.4 1.2 0.043 0.1 0.2 0.3 0.8 0.1 165 Comparative Example 5 4.7 0.09 3.2 1.5 2 0.003 0.4 One 1.4 0.4 0.5 105 Comparative Example 6 6.9 0.08 4.1 1.4 3.2 0.03 0.5 0.1 0.6 0.05 0.05 143 Comparative Example 7 9.5 0.04 4.3 2.1 1.7 0.02 1.2 1.2 1.7 0.2 111 Comparative Example 8 4.7 0.03 1.1 1.8 0.6 0.003 0.5 0.5 1.0 0.5 0.75 69 Comparative Example 9 4.0 0.08 2.2 1.5 1.1 0.006 0.2 0.2 0.4 0.5 0.5 92 Comparative Example 10 4.7 0.05 4.2 1.32 3.4 0.038 0.5 0.2 0.7 0.5 0.015 233 Comparative Example 11 6. 0.08 4.4 0.4 3.5 0.037 0.2 0.4 0.4 1.0 1.2 0.012 221 Comparative Example 12 3.5 0.06 2.8 0.32 3.2 0.032 0.1 0.2 0.5 0.8 0.8 0.03 216 Comparative Example 13 6.5 0.05 1.2 1.7 2.4 0.03 0.2 0.2 1.2 0.8 101

division C Si Mn P S Fe Content (% by weight) 0.025 0.02 0.24 0.007 0.004 Remainder

Base material Root gap Angle Lamination electric current Voltage Welding speed Heat input HT780,
35mmt 5 mm 40 degrees 15pass 280 31 25-40
Cm / min 13-21
KJ / cm

division Electron Welding Weldability The tensile strength
(N / mm2) Impact toughness
Ve-60 ℃ (Joules) Crack occurrence Inventive Example 1 ⊙ 650 85 - Inventive Example 2 ○ 731 100 - Inventive Example 3 ⊙ 785 85 - Inventive Example 4 ○ 780 60 - Inventive Example 5 ○ 654 79 - Inventive Example 6 ○ 850 105 - Inventive Example 7 ⊙ 830 89 - Inventive Example 8 ⊙ 754 90 - Inventive Example 9 ○ 690 81 - Inventive Example 10 ○ 790 65 - Inventive Example 11 ○ 695 71 - Inventive Example 12 ○ 825 65 - Comparative Example 1 × 610 80 - Comparative Example 2 × 755 40 - Comparative Example 3 ○ 665 24 - Comparative Example 4 ○ 784 78 Occur Comparative Example 5 △ 851 46 Occur Comparative Example 6 △ 700 38 - Comparative Example 7 × 787 62 - Comparative Example 8 △ 654 35 - Comparative Example 9 ○ 784 37 - Comparative Example 10 ○ 843 85 Occur Comparative Example 11 △ 812 80 Occur Comparative Example 12 ○ 774 90 Occur Comparative Example 13 △ 673 40 -

As shown in Table 4, Inventive Examples 1 to 12 show excellent welding workability and mechanical properties (tensile strength and low temperature impact toughness) and crack resistance.

On the contrary, Comparative Example 1 is outside the scope of the present invention in the content of Mn, welding workability and tensile strength was insufficient, and in the case of Comparative Example 2 in the content of Si outside the scope of the present invention, weldability and impact toughness This was degraded.

In addition, Comparative Example 3 was lowered the impact toughness of the content of Ni out of the range of the present invention, Comparative Example 4 is a case where the content of B is out of the range of the present invention, the crack resistance is reduced.

In Comparative Example 5 in which the sum of Cr, Mo, and V contents were outside the range of the present invention, impact toughness was not preferable, and crack resistance was lowered.

Comparative Examples 6 and 7 in which the content of Mg was out of the range of the present invention deteriorated impact toughness and weldability, respectively.

In addition, in the case of Comparative Examples 8, 9, and 13 in which the formula F value did not fall within the scope of the present invention, there was no problem in crack resistance, but the impact toughness was insufficient, and, in contrast, Comparative Example 10, in which the F value exceeded the scope of the present invention, In case of 11 and 12, impact toughness was good, but crack resistance was lowered.

Figure 1 is a graph showing the formula F value and -60 ℃ low temperature impact toughness and crack generation region.

Claims (1)

Flux-filled wire in which flux is filled in the steel shell, wherein the weight% is based on the total weight of the wire, C: 0.03 to 0.11%, TiO ₂ : 3.0 to 10%, Mn: 1.0 to 4.5%, Si: 0.3 to 2.0%, B: 0.002 ~ 0.04%, Ni: 0.5 ~ 3.5%, Mg: 0.1 ~ 1.5%, Al: 0.01 ~ 0.8%, at least one selected from the group consisting of Cr, Mo and V contains 0.1 ~ 1.2% The remainder is made of Fe in the steel shell, iron in the flux and unavoidable impurities, and the flux filling wire for gas shielded arc welding for high tensile strength steel, characterized in that the following formula F value satisfies 110 to 210.

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