KR100550333B1 - Metal cored wire for twin tandem arc welding - Google Patents

Abstract

      A metal cored wire for two electrode welding is provided.

The wire of the present invention, the weight percent to the wire, C: 0.02 to 0.15%, deoxidizer: 1.5 to 4.0%, F conversion in fluoride: 0.01 to 0.25%, iron content: 10 to 22.5%, balance iron and unavoidable impurities Consisting of; Oxygen and nitrogen content in the iron powder is 0.2% or less, 0.003% or less, respectively, C / F ratio is controlled to 0.3 ~ 6.0.

The wire of the present invention imparts excellent porosity and workability when welding a primer coated steel sheet.

Iron, nitrogen and oxygen content in iron, fluoride

Description

  Metal cored wire for two-electrode high-speed fillet welding {Metal cored wire for twin tandem arc welding}

The present invention relates to a metal-cored wire for gas shielded arc welding, which is used for high-speed fillet welding of primer coated steel sheet while forming one molten base with two electrodes. More specifically, the oxygen and nitrogen content in iron powder and deoxidizer and The present invention relates to a metal-cored wire for arc welding of two-electrode gas shielded arc, in which the fluoride content is properly controlled and excellent in weldability and porosity resistance.

Recently, high speed and high efficiency have been achieved in manufacturing shipbuilding, bridges, and steel structures. In order to meet these demands, twin tandem welding techniques are being carried out in which one electrode is formed of two electrodes and simultaneously welds both sides of the fillet. However, in order to prevent corrosion and oxidation caused by long-term storage, the steel sheets used for welding are generally coated with primers. ) And a blow hole (blow hole), such as welding quality is deteriorated and there is a problem that additional air generation occurs.

Japanese Unexamined Patent Application Publication No. 6-218578 is an example of a conventional technique for solving such a problem. The above publication suggests that the porosity resistance can be secured at a certain level because the amount of TiO ₂ added and the amount of deoxidizer and iron oxide added to the arc stabilizer or the slag forming agent are controlled to a predetermined value.

In addition, Korean Patent Laid-Open No. 2001-0061851 proposes to provide a metal-cored wire having excellent porosity and workability under high speed welding by appropriately adjusting the content and ratio of metal iron, slag forming agent, and fluoride.

However, these methods are basically related to titania-based flux-filled wire which forms slag on the surface of the deposited metal, which is mainly composed of TiO ₂ . There is always a possibility of deterioration, and also due to the addition of the slag forming agent is relatively low iron content in the flux, there is a limit to improve the welding speed and welding efficiency.

In addition, Japanese Unexamined Patent Publication No. 63-154267 discloses a method of improving welding speed by using a metal cored wire for magnet welding mainly composed of iron, but in this method, the improvement in porosity resistance was not sufficient.

Therefore, the present invention is to solve the problems of the prior art described above, by controlling the oxygen and nitrogen content in iron powder, and by controlling the content of the deoxidizer and fluoride appropriately, excellent porosity resistance in two-electrode high-speed tandem welding It is an object of the present invention to provide a metal cored wire for welding which can achieve good workability.

The present invention for achieving the above object,

Weight percentage of wire: C: 0.02-0.15%, deoxidizer: 1.5-4.0%, F equivalent in fluoride: 0.01-0.25%, iron content: 10-22.5%, balance iron and unavoidable impurities; Oxygen and nitrogen content in the iron powder is 0.2% or less, 0.003% or less, respectively, and relates to a metal-cored wire for welding two-electrode high-speed fillet, the C / F ratio is controlled to 0.3 ~ 6.0.

Hereinafter, the composition components of the wire of the present invention and the reason for limitation thereof.

C stabilizes the arc in two-electrode welding, reduces spatter generation, and increases the arc force to suppress the penetration of oxidized inclusions (MnO, Al ₂ O ₃ , SiO _2, etc.) into the weld metal, thereby obtaining a healthy weld. do. It also serves to maintain the toughness and strength of the weld.

In the present invention, the content of C is limited to 0.02% to 0.1% by weight of the wire (hereinafter referred to as only%). If the content is less than 0.02%, the arc force is lowered to facilitate welding defects, and the strength and toughness of the weld metal is lowered. If the content is more than 0.1%, the arc stability is deteriorated and the spatter is excessively generated. In addition to the deterioration, excessively added C combines with hydrogen (H) to generate methane gas (CH ₄ ), thereby causing pits and blowholes.

The wire of the present invention includes a deoxidizer such as Si, Mn, Mg, Ti, Al, etc., and this deoxidizer mainly serves to reduce the oxygen content in the weld metal to form a healthy weld metal, and additionally, as an arc stabilizer. It also plays a role.

In the present invention, the total amount of such deoxidant is limited to 1.5-4%. If the content of the deoxidizer is less than 1.5%, the deoxidation in the weld metal is insufficient, which leads to deterioration of the fault resistance due to excessive intercalation of the oxide, as well as the oxygen content of the weld metal, which leads to a decrease in toughness. This is because the weldability deteriorates due to an excessive amount of.

Fluoride reduces the dehydrogenation inside the weld metal and lowers the solidification temperature of the melt to help release the combustion gases and improve the porosity.

Hydrogen, the main component of the primer flue gases forming pits and blowholes, is significantly reduced by the proper addition of fluorides, and these fluorides also stabilize the arc and reduce the generation of spatters. Fluoride may be added in the form of NaF, Na ₃ AlF ₆ , K ₂ SiF ₆ , CaF _2, LiF, MgF _2, and the like.

In the present invention, the amount of F in the fluoride is limited to 0.01 to 0.25%. This is because if the converted amount is less than 0.01%, various effects of addition cannot be obtained. On the other hand, if the amount exceeds 0.25%, excessive spatter and fume are generated and the appearance of beads deteriorates.

Meanwhile, as described above, carbon (C) combines with hydrogen during the welding process to form methane (CH ₄ ) gas, which is one of the causes of pits and blow holes. Therefore, the present inventors have focused on the fact that such welding defects can be prevented by adding a fluoride capable of controlling hydrogen at an appropriate ratio, thereby finding an appropriate C / F ratio.

That is, the present invention is characterized by limiting the C / F ratio to 0.3 to 6.0 for good work performance and excellent porosity resistance. If the ratio is less than 0.3, the F content is too high compared to the C content, so that the solidification rate of the molten metal becomes too slow, resulting in uneven bead appearance and excessive slag on the surface of the bead. Since the amount is insufficient and the dehydrogenation is insufficient, it is easy to generate the CH ₄ gas, and accordingly, the probability of blow hole in the weld metal may be increased.

The wire of the present invention also contains iron.

Iron accounts for most of the metal-based fluxes filled in the steel sheath and improves the work efficiency by increasing arc stability and welding speed.

In the present invention, the iron content is limited to 10 to 22.5%. If the content is less than 10%, the welding workability is lowered and the spatter amount is not only high, but the welding amount is not available, so that high-speed welding of more than 1.5 m / min is impossible. This is because the arc stability deteriorates and the generation of spatters increases.

In the present invention, the oxygen and nitrogen content in the iron powder is limited to a predetermined range. First, oxygen contained in iron increases the oxygen content in the weld metal to deteriorate the toughness of the weld metal and causes defects on the surface or inside of the bead, so it must be controlled to 0.2% or less, and the nitrogen contained in the iron is also deposited. It should be controlled to 0.003% or less because it increases the nitrogen content inside the metal and not only deteriorates toughness but also causes pit and blow hole.

In addition, the present invention may include Ni in addition to the content range of 0.3 to 5.0%, because Ni has an effect of improving the arc stability and porosity. However, when the Ni content is less than 0.3%, the effect of Ni addition cannot be obtained. When the Ni content is more than 5.0%, not only the strength of the weld metal is excessively increased but also the anxiety of the arc causes poor bead appearance.

Hereinafter, the present invention will be described in detail through examples.

(Example)

As shown in Table 1, metal-cored wires having different compositions were prepared with wire diameters of 1.6 mm. At this time, the mild steel sheath constituting the wire was used as a weight% relative to the weight of the sheath containing C: 0.025%, Si: 0.015%, Mn: 0.20%, P: 0.010%, S: 0.015%.

 division Flux component (% by weight) Oxygen content in iron Nitrogen content in iron Ratio of C / F  Remarks C Si Mn Mg Al Ti Ni Deoxidation Fluoride F conversion amount iron content Inventive Example 1 0.06 0.8 2 0.5 0.1 0.1 3.4 0.01 12 0.15 0.001 6.00 Inventive Example Inventive Example 2 0.12 0.9 1.5 0.5 2.9 0.08 18 0.09 0.0005 1.50 Inventive Example Inventive Example 3 0.11 0.6 0.8 0.1 0.1 1.6 0.03 20 0.08 0.002 3.67 Inventive Example Inventive Example 4 0.05 0.9 0.8 0.2 1.7 0.16 18 0.07 0.0008 0.31 Inventive Example Inventive Example 5 0.1 One 1.5 0.5 0.1 3.1 0.04 16 0.05 0.0007 2.50 Inventive Example Inventive Example 6 0.1 1.6 1.2 0.2 0.1 3.1 0.25 15 0.08 0.002 0.40 Inventive Example Inventive Example 7 0.09 One 1.5 0.6 0.2 0.1 3.3 0.05 21 0.12 0.001 1.80 Inventive Example Inventive Example 8 0.02 1.4 0.9 0.5 0.5 3.3 0.04 11 0.02 0.002 0.50 Inventive Example Inventive Example 9 0.09 0.8 0.7 0.3 1.5 0.03 17 0.06 0.0009 3.00 Inventive Example Inventive Example 10 0.12 1.1 1.2 0.6 0.1 4.5 3 0.05 19 0.08 0.05 2.40 Inventive Example Comparative Example 11 0.045 0.4 One 0.1 0.2 1.7 0.007 14 0.1 0.005 6.43 Comparative example Comparative Example 12 0.18 1.5 1.1 0.2 0.3 3.1 0.08 16 0.05 0.0009 2.25 Comparative example Comparative Example 13 0.01 1.4 1.1 0.2 0.8 2.7 0.03 15 0.06 0.004 0.33 Comparative example Comparative Example 14 0.03 0.4 0.5 0.3 1.2 0.05 20 0.04 0.002 0.60 Comparative example Comparative Example 15 0.05 1.8 2 0.5 0.5 4.8 0.06 19 0.12 0.002 0.83 Comparative example Comparative Example 16 0.09 0.8 1.8 0.4 0.2 0.1 3.3 0.20 8 0.1 0.0008 0.45 Comparative example Comparative Example 17 0.1 0.9 1.5 0.2 0.5 1.5 3.1 0.28 21 0.09 0.001 0.36 Comparative example Comparative Example 18 0.15 0.5 1.6 0.2 0.2 2.3 0.02 18 0.08 0.001 7.50 Comparative example Comparative Example 19 0.06 0.5 1.3 0.1 0.2 0.5 2.6 0.04 16 0.25 0.002 1.50 Comparative example Comparative Example 20 0.08 0.8 1.2 0.1 0.1 2.2 0.10 11 0.08 0.004 0.80 Comparative example Comparative Example 21 0.03 1.6 1.2 0.2 0.1 3.1 0.20 15 0.08 0.002 0.15 Comparative example Comparative Example 22 0.11 1.4 One 0.5 0.1 1.2 3 0.010 15 0.08 0.002 11.00 Comparative example Comparative Example 23 0.03 0.8 1.5 0.3 5.5 2.6 0.05 15 0.04 0.002 0.60 Comparative example

The welding wires thus prepared are coated with 12-mm thick 150-mm-2000 mm T-Fillet inorganic zinc primer with a primer thickness of 40-50 um under the twin tandem 1 pool method under the welding conditions shown in Table 2. It was used to weld the steel sheet, and the arc stability, porosity resistance, and bead appearance of the welding were evaluated and shown in Table 3. Here, the porosity resistance was evaluated by the degree of blow hole generation and the pit generation of the bead surface inside the fracture surface of the back side of the weld per 2 m of welding length, and the results are also shown in Table 3. On the other hand, in Table 3, (circle) is excellent, (circle) is good, (triangle | delta) is normal, and x represents a defect.

Leading and trailing poles (current / voltage)  Welding speed  Welding  Protective gas  460 A / 42 V, 410 A / 37 V  1500mm / min  5 mm  Ar + 20% CO2, 18ℓ / min

 division  No Test result  Comprehensive Evaluation Bead Appearance Arc stability Air resistance Inventive Example One ○ ○ ○ ○ Inventive Example 2 ○ ◎ ○ ○ Inventive Example 3 ◎ ○ ○ ○ Inventive Example 4 ○ ◎ ○ ○ Inventive Example 5 ○ ◎ ○ ○ Inventive Example 6 △ ○ ○ ○ Inventive Example 7 ○ ○ ◎ ○ Inventive Example 8 ○ ○ ◎ ○ Inventive Example 9 ○ ◎ ◎ ◎ Inventive Example 10 ○ ◎ ◎ ◎ Comparative example 11 ○ △ × △ Comparative example 12 △ × ○ × Comparative example 13 △ △ △ △ Comparative example 14 ○ △ × △ Comparative example 15 △ × ○ △ Comparative example 16 × △ ○ △ Comparative example 17 △ × ○ × Comparative example 18 ○ ○ × × Comparative example 19 ○ ○ × × Comparative example 20 ○ △ × × Comparative example 21 × △ × × Comparative example 22 ○ ○ × × Comparative example 23 × × ○ ×

As shown in Table 3, the invention examples (1 to 10) in which the wire composition was properly controlled showed excellent results in terms of bead appearance, arc stability, and porosity resistance, and the invention examples in which Ni was added in a predetermined range (9, 10) showed better porosity resistance and arc stability.

On the other hand, Comparative Example (11) in which the F conversion amount of the fluoride and the C / F ratio were outside the scope of the present invention was very poor in porosity, and the comparative examples (12 to 15) in which the amount of carbon, the amount of deoxidizer, etc. were excessive or excessive. Bead appearance, arc stability, and porosity were generally poor.

In addition, the C / F ratio of the comparative examples (18, 21, 22) outside the scope of the present invention showed poor porosity, and Comparative Examples (19-20) with excessive oxygen and nitrogen content in iron also had poor porosity resistance. .

As described above, the present invention provides a metal-cored wire for two-electrode that improves porosity and improves workability when welding a primer coated steel sheet by appropriately controlling the addition amount of iron, deoxidizer and fluoride, as well as the ratio of C and F. That has a useful effect.

Claims (2)

C: 0.02 to 0.15% by weight relative to the wire, at least one deoxidizer selected from Si, Mn, Mg, Ti and Al: 1.5 to 4.0%, NaF, Na ₃ AlF ₆ , K ₂ SiF ₆ , CaF ₂ , LiF And F conversion amount of at least one fluoride selected from MgF ₂ : 0.01 to 0.25%, iron content: 10 to 22.5%, balance iron and inevitable impurities; Oxygen and nitrogen content in the iron powder is 0.2% or less, 0.003% or less, respectively, C / F ratio metal cored wire for high-speed fillet welding is controlled to 0.3 ~ 6.0 The metal-cored wire for welding of two-electrode high-speed fillet according to claim 1, wherein Ni is further added in an amount of 0.3 to 5.0% .