JP2009082947A - Flux-cored wire for electrogas arc welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flux-cored wire for electrogas arc welding having excellent workability in the one-electrode electrogas arc welding of a thick steel plate, and capable of obtaining a weld metal of high strength and excellent impact performance. <P>SOLUTION: The flux-cored wire for electrogas arc welding contains, by mass, 0.03-0.07% C, 0.3-0.6% Si, 1.8-2.0% Mn, 0.9-1.2% Ni, ≤0.1% Cr, ≤0.3% Cu, 0.3-0.8% Mo, 0.10-0.27% Ti, 0.008-0.014% B, 0.15-0.30% Mg, ≤0.05% Al, ≤0.025% P, ≤0.025% S, and 1.0-2.0% slag generating agent while containing 0.4-0.7% F in the slag generating agent. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a flux-cored wire for one-electrode electrogas arc welding capable of vertical one-pass welding of thick steel plates such as YP460 steel.

  Electrogas arc welding is applied to a wide range of fields such as ships, oil storage tanks and bridges as a highly efficient vertical welding method. In recent years, the economic and industrial development of China and East Asian countries has been remarkable, and with the increase of goods flow, the size of container ships has been increasing rapidly for the purpose of efficient transportation of container cargo.

Along with the increase in size of container ships, thickening of ship side shells or hatch coaming is progressing. When the number of containers loaded is 8000 TEU, when steel material with a yield strength of 390 N / mm ² is used, the applicable plate thickness is 80 mm. It will be about. On the other hand, by setting the yield strength of the steel material to 460 N / mm ² or more, the applicable plate thickness can be reduced to about 60 mm, and the weight of the hull can be reduced. As a result, fuel efficiency is improved and welding construction efficiency is also improved. Accordingly, the strength of steel materials has been increased, and the development of a flux-cored wire for electrogas arc welding corresponding to that has been desired.

Conventionally, studies have been made on the application of electrogas arc welding to high-strength steel materials having a yield strength of 460 N / mm ² or more. For example, Patent Document 1 proposes an electrogas arc welding method in which the brittle fracture resistance is improved by defining the chemical composition of the wire and the chemical composition of the weld metal.

  However, in order to apply such a high-strength steel material, it is important to ensure the strength of the welded joint. In the case of large heat input welding such as electrogas arc welding, the width of the heat-affected zone of the steel material is large. For this reason, there is a problem that the softening width of the steel material due to the heat effect increases, and sufficient joint strength cannot be secured.

  Therefore, in order to solve such a problem, it has been proposed to increase the strength of the weld metal as compared with the prior art to restrain the plastic deformation of the heat-affected zone and secure the joint strength.

JP 2005-329460 A

  However, simply adding more alloy components than conventional wires to increase the strength will increase the viscosity of the slag during welding, resulting in poor workability and reduced base metal dilution. However, there is a problem that the toughness is deteriorated.

  The present invention has been made in view of such a problem, and is capable of obtaining a weld metal having excellent workability in one-electrode electrogas arc welding of a thick steel plate, and further having high strength and excellent impact performance. An object of the present invention is to provide a flux-cored wire for electrogas arc welding.

The flux cored wire for electrogas arc welding according to the present invention has a pair of welded plates formed with a groove whose front side is wider than the back side so that the groove extends in the vertical direction, and the welded wire Applying a sliding copper plate that slides upward relative to the welded plate to the surface side of the plate, applying a backing material fixed to the welded plate to the back side of the welded plate, In a flux-cored wire used for vertical butt welding in the groove by one-electrode electrogas arc welding, C: 0.03 to 0.07 mass% per total mass of the wire,
Si: 0.3 to 0.6% by mass,
Mn: 1.8 to 2.0% by mass,
Ni: 0.9 to 1.2% by mass,
Mo: 0.3 to 0.8 mass%,
Ti: 0.10 to 0.27% by mass,
B: 0.008 to 0.014% by mass,
Mg: 0.15 to 0.30 mass%,
Slag generating agent: 1.0 to 2.0% by mass,
F: 0.4 to 0.7% by mass of the slag forming agent (F converted value per wire total mass),
Containing
Cr: 0.1% by mass or less,
Cu: 0.3 mass% or less,
Al: 0.05% by mass or less,
P: 0.025 mass% or less,
S: 0.025 mass% or less,
It is characterized by restricting to.

Another flux cored wire for electrogas arc welding according to the present invention is characterized by containing CO ₂ : 0.10 to 0.25% by mass with respect to the total mass of the wire.

  According to the present invention, it is possible to obtain a weld metal having improved workability in one-electrode electrogas arc welding of a thick steel plate, high strength, and excellent impact performance.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is a schematic view showing a method of vertical butt welding by one-electrode electrogas arc welding using the flux-cored wire of the present invention. FIG. 1 is a view showing the inside of a V groove of a steel plate 1 to be welded. The right side of the drawing is the front surface of the steel plate to be welded and the left side is a back surface. The backing material 3 fixed to the welded plate 1 is applied to the groove portion on the back side of the welded plate 1, and the groove portion on the surface side of the welded plate 1 is directed upward with respect to the welded plate 1. The sliding copper plate 2 that slides is applied. A shield gas supply unit 4 for supplying a shield gas into the groove is provided on the upper portion of the sliding copper plate 2, and the sliding copper plate 2 itself is cooled by supplying cooling water via a pipe 8. Then, the welding electrode 7 is inserted into the groove from the surface side of the welded plate 1, an arc is generated from the weld electrode 7, and the sliding copper plate 2 is raised while weaving in the thickness direction of the welded plate 1. The welded plate 1 is welded. Thereby, molten slag and molten pool 6 are formed, and molten pool 6 is solidified to form weld metal 5. A slag relief groove 9 is formed between the sliding copper plate 2 and the welded plate 1.

  In the vertical butt welding by such one-electrode electrogas arc welding, the present inventors have intensively studied. As a result, the workability is good even in a high-strength welded joint by further appropriately defining the chemical composition of the wire. It has been found that the impact performance of weld metal can be enhanced.

  In order to increase the restraining force that restrains the plastic deformation of the heat affected zone, it is necessary to increase the strength of the weld metal as compared with the prior art, so it is necessary to increase the alloy components such as Si, Mn, and Mo of the wire. However, when these components increase, the viscosity of the molten metal and molten slag increases, and the slag cannot be discharged well from the slag escape groove shown in FIG. Therefore, there is a problem that slag accumulates excessively in the molten pool, the arc becomes unstable, the penetration becomes shallow, poor fusion is likely to occur, the strength becomes too high, and the toughness deteriorates.

  In addition, for toughness degradation, conventionally, improvement has been attempted by adding Ni, which mainly has an effect of stabilizing toughness. However, in such a component system mainly composed of Ni, it has been recognized that when an alloy component is added to secure joint strength and the strength is increased, the toughness tends to deteriorate.

  Therefore, the present inventors have eagerly developed a wire component system that can improve the above-described welding workability, that is, a slag discharge property and a weld metal with good impact performance. As a result of examination, it has become clear that it is effective to optimize the alloy components added to the wire, and to strictly define the amount of slag forming agent and the amount of F thereof.

  As described above, when the viscosity of the molten metal and molten slag is high, the slag discharge performance is deteriorated, but the increase in the viscosity of the molten metal and molten slag is suppressed by adjusting the addition amount of Si and Mn so as not to be excessive. be able to. Furthermore, by increasing the amount of the slag generating agent, the molten slag can easily flow into the slag escape groove, and it is possible to prevent molten metal having a high viscosity from blocking the slag escape groove. Moreover, the viscosity of molten slag can be lowered | hung and discharge property can be improved by increasing F amount of slag production | generation agents.

  Regarding the impact performance, it has been found that by reducing the amount of Ni and adding Mo as compared with the prior art, the structure can be made finer and effective in securing the strength and toughness of the thick plate. However, if Ni is excessively reduced, the effect of lowering the transition temperature is lost, and the toughness at low temperatures deteriorates. On the other hand, if the amount of Mo is excessive, the quenching effect is high, so that the strength becomes too high and the toughness deteriorates, and the optimization of the amounts of Ni and Mo is important for stabilizing the strength and toughness of the weld metal.

  Hereinafter, the reasons for adding components and limiting the composition of the flux-cored wire of the present invention will be described.

“C: 0.03 to 0.07 mass%”
C is an element indispensable for ensuring the strength of the weld metal, but if added excessively for the purpose of increasing the strength, the toughness deteriorates, so that C is added more than before to increase the strength. Is not preferred. If the mass of C is less than 0.03% by mass, the strength of the weld metal decreases, and the desired strength cannot be obtained. On the other hand, when C exceeds 0.07 mass%, the strength of the weld metal becomes too high and the toughness deteriorates. Examples of the C source include C and C in the steel outer shell, C in iron powder and metal powder, and the like.

“Si: 0.3 to 0.6 mass%”
Since Si increases the strength of the weld metal, it needs to be added more than before. Si also has the effect of reducing the oxygen content of the weld metal and improving toughness as a deoxidizer. When the mass of Si is less than 0.3% by mass, the toughness of the weld metal deteriorates. On the other hand, when Si exceeds 0.6% by mass, the viscosity of the molten slag increases, the slag discharge performance is poor, the arc becomes unstable, and fusion failure occurs. Examples of the Si source include Si, Fe—Si, Fe—Si—Mn, Fe—Si—B, Fe—Si—Mg, and REM—Ca—Si in a steel shell.

“Mn: 1.8 to 2.0 mass%”
Mn also needs to be added more than before in order to increase the strength of the weld metal. Mn also has the effect of reducing the oxygen content of the weld metal and improving toughness as a deoxidizer. If the mass of Mn is less than 1.8% by mass, the strength of the weld metal is lowered and the intended strength cannot be obtained. On the other hand, when Mn exceeds 2.0 mass%, the strength of the weld metal becomes too high and the toughness deteriorates. Examples of the Mn source include Mn, steel Mn, Fe—Mn, and Fe—Si—Mn in the steel outer shell.

“Ni: 0.9 to 1.2 mass%”
Ni is an austenite forming element and has the effect of stabilizing the toughness of the weld metal as described above. However, in order to ensure the toughness by the effect of refining the structure by adding an alloy component such as Mo, it is necessary to reduce the amount of Ni added to the extent that the toughness does not become unstable. However, if the mass of Ni is less than 0.9 mass%, the toughness of the weld metal becomes unstable and deteriorates. On the other hand, if Ni exceeds 1.2% by mass, the strength becomes too high and the toughness deteriorates. Note that Ni sources include metal Ni, Fe—Ni, Ni—Mg, and the like.

“Mo: 0.3 to 0.8 mass%”
In order to increase the strength of the weld metal, Mo needs to be added more than before. Mo is a ferrite-forming element, has an effect of improving the hardenability of the weld metal, and is an element effective for refining the solidified structure. Therefore, Mo improves toughness. If the mass of Mo is less than 0.3% by mass, the strength of the weld metal decreases, and the intended weld joint strength cannot be obtained. On the other hand, when Mo exceeds 0.8 mass%, the strength increases and the toughness deteriorates. As the Mo source, there are metal Mo, Fe-Mo, and the like.

“Ti: 0.10 to 0.27 mass%”
Ti has the effect of refining the weld metal structure and improving toughness by a synergistic effect with B. If the mass of Ti is less than 0.10% by mass, the effect of refining the structure cannot be obtained, and the toughness of the weld metal deteriorates. On the other hand, when Ti exceeds 0.27 mass%, Ti becomes excessive in the weld metal and the toughness deteriorates. The Ti source includes metal Ti, Fe—Ti, and the like.

“B: 0.008 to 0,014 mass%”
B has the effect of making the weld metal structure fine and improving toughness by synergistic effect with Ti with a small amount of addition. If the mass of B is less than 0.008 mass%, the effect of refining the structure cannot be obtained, and the toughness of the weld metal deteriorates. On the other hand, if B exceeds 0.014% by mass, B becomes excessive in the weld metal, the strength becomes too high, and the toughness deteriorates. Examples of the B source include Fe—B, Fe—Si—B, and B ₂ O ₃ .

“Mg: 0.15 to 0.30 mass%”
Mg as a deoxidizer has the effect of reducing the oxygen content of the weld metal and improving toughness. If the mass of Mg is less than 0.15% by mass, the effect of reducing the oxygen content of the weld metal cannot be obtained, and the toughness of the weld metal deteriorates. On the other hand, if Mg exceeds 0.30% by mass, the arc becomes unstable and spattering occurs frequently. Note that the Mg source includes metal Mg, Al—Mg, Fe—Si—Mg, Ni—Mg, and the like.

“Al: 0.05% by mass or less”
When the Al content of the weld metal is high, the effect of refining the structure due to the Ti oxide is suppressed and the toughness deteriorates, so Al is suppressed to 0.05% by mass or less.

“Cu: 0.3 mass% or less”
Cu is not intentionally added. However, although it may inevitably be contained in an amount of 0.3% by mass or less due to plating of the outer peripheral surface of the flux-cored wire, such an amount is allowed.

"Cr: 0.1 mass% or less"
Cr is a ferrite-forming element and has the effect of improving the hardenability of the weld metal, but the effect is small compared to Mo, intentionally not added, and inevitably contained 0.1% by mass or less Is acceptable.

“P, S: 0.025 mass% or less”
When P and S are high, hot cracking is likely to occur, so the content is suppressed to 0.025% by mass or less.

"Slag generator: 1.0 to 2.0 mass%"
The slag generating agent is indispensable for stabilizing the welding workability such as arc stabilization, spatter reduction, and prevention of falling. The weld metal component of the present invention has a large amount of alloying elements and a large amount of the component that oxidizes the molten metal. Due to the slag, the slag discharge performance is remarkably deteriorated. Therefore, the deterioration of workability can be suppressed by increasing the amount of the slag forming agent as compared with the conventional case so that the molten metal does not come to the slag escape groove. When the amount of the slag generating agent is less than 1.0% by mass, the amount of slag is insufficient, the molten metal closes the slag escape groove, and the slag discharge performance is deteriorated, resulting in poor fusion. Furthermore, the slag cannot suppress the molten metal, and is easily melted down. On the other hand, if the amount of slag exceeds 2.0% by mass, the amount of slag to be supplied becomes excessive, and on the contrary, the slag discharge performance is deteriorated. Therefore, the arc becomes unstable and poor fusion occurs.

"F amount of slag forming agent: 0.4 to 0.7 mass% (F converted value per total mass of wire)"
It is not possible to improve workability simply by defining the amount of the slag generating agent. Therefore, the amount of F of the slag forming agent was examined. F has the effect of lowering the viscosity of the molten slag and improving the dischargeability of the slag. If the mass is less than 0.4% by mass, the slag discharge property becomes poor, the arc becomes unstable, and poor fusion occurs. On the other hand, if F exceeds 0.7% by mass, the viscosity of the molten slag becomes too low and the discharge property becomes too good, so that the molten metal cannot be held and the molten metal is likely to fall off. The amount of F is more preferably 0.5 to 0.7% by mass. Examples of the F source include CaF ₂ , BaF ₂ , NaF, K ₂ SiF ₆ , SrF ₂ , AlF ₃ , MgF ₂ , and LiF. The F amount is a value obtained by converting the amount of these compounds into an F amount, and is the content per total mass of the wire.

“CO ₂ : 0.10 to 0.25% by mass”
CO ₂ is usually added into the wire by carbonate. CO ₂ generated by the decomposition of carbonate has the effect of stably spreading the arc. By adding carbonate to the wire, the arc is spread and stable, so that the molten slag is stably discharged from the slag escape groove. If the amount of CO ₂ is less than 0.10% by mass, the effect cannot be obtained, and poor fusion tends to occur. On the other hand, if the amount of CO ₂ exceeds 0.25% by mass, the amount of gas generated becomes excessive, and the arc tends to be slightly unstable. As the _carbonate, there is _{CaCO 2, MgCO 2, BaCO 2} , Li 2 CO 2, Na 2 CO 2, Sr 2 CO 2 or the like. The CO ₂ amount is a CO ₂ amount conversion value of these carbonates.

As the slag-forming _{agent, SiO 2, CaO, Na 2} O, MgO, Al 2 O 3, Li 2 O, CaF 2, BaF 2, NaF, SrF 2, K 2 O, K 2 SiF 6, AlF 3 there are _{MgF 2, LiF, CaCO 3,} MgCO 3, BaCO 3, Li 2 CO 3, Na 2 CO 3, Sr 2 CO 3 or the like.

The balance of the flux-cored wire is inevitable impurities other than Fe, B ₂ O ₃ O, REM, and the like. Of the balance, Fe contains 90% by mass or more, and the Fe source includes steel outer skin, iron powder, Fe alloy Fe, and the like.

  The flux filling rate of the flux-cored wire of the present invention is 20 to 30% by mass.

  In the electrogas arc welding of the present invention, since the influence of the base material is not a little, as the applicable steel plate, rolled steel for general structure, rolled steel for welded structure, high yield point steel plate for welded structure, rolled steel for building structure, Of the steel plates used for ships, the ranges shown in Table 1 below (unit: mass%) are preferred. The welded steel plates used in this example are those shown in Table 2 below (unit: mass%). The test steel sheet has a thickness of 60 mm, a width of 500 mm, and a length of 1000 mm. In these Tables 1 and 2, the carbon equivalent Ceq is expressed by Equation 1 below.

  Table 3 below shows test conditions, Table 4 shows welding conditions, and one-pass welding was performed under the conditions shown in Tables 3 and 4. And workability | operativity was confirmed during welding. After welding, a UT inspection was performed to confirm the presence of poor fusion. In addition, each 100 mm on the start side and crater side where welding was not stable was excluded from inspection. Therefore, the effective length is 800 mm. In addition, what melted down on the way becomes shorter. In the range of the effective length, the case where no fusion failure was observed was marked as ◎, the case where the fusion failure length was less than 2% was marked as ◯, and the case where the fusion length was over 2% was marked as ×. The wire diameter is 1.6 mm.

開先形状：Ｖ開先

Groove shape: V groove

As for the weld metal impact test, the impact value at −20 ° C. was measured by the method defined in JIS Z 3128, and the average of the three values was determined to have good impact performance when the average value was 53 J or more. As for the strength of the weld metal, an NK U1A test piece was used at the position of the center of the weld metal (test piece diameter: 10 mm, gauge distance: 50 mm), and the target strength was 600 N / mm ² or more.

Tables 5 and 6 below show the chemical composition (unit: mass%) of the wire. The characteristics of the weld metal when welded with these wires are shown in Table 7 below. In the wires of Examples 1 to 14 having the compositions shown in Tables 5 and 6, welding workability was good and toughness was good, and the target weld metal strength was obtained. In the wire of Comparative Example 15, the amount of F in the wire slag forming agent was less than 0.4% by mass, the slag discharge performance was deteriorated, and poor fusion occurred. In the wire of Comparative Example 16, the C content of the wire was less than 0.03% by mass, the Mo content was less than 0.3% by mass, and the intended strength was not obtained. In Comparative Example 17, the C content of the wire exceeds 0.07 mass%, the Mn content exceeds 2.1 mass%, the Mo content exceeds 0.8 mass%, and the strength of the weld metal becomes too high. The toughness deteriorated. In Comparative Example 18, the amount of wire Si was less than 0.3% by mass, and the toughness deteriorated. In Comparative Example 19, the Ti amount of the wire exceeded 0.27 mass%, the B amount exceeded 0.014 mass%, the strength of the weld metal became too high, and the toughness deteriorated. In Comparative Example 20, the amount of the slag forming agent of the wire exceeded 2.0% by mass, the slag discharge performance was deteriorated, and poor fusion occurred. In Comparative Example 21, the amount of the slag generating agent of the wire was less than 1.0% by mass, the slag discharge performance was deteriorated, and poor fusion occurred. Furthermore, the weld metal melted down during welding. In Comparative Example 22, the amount of Si in the wire exceeded 0.6% by mass, the slag discharge performance deteriorated, and poor fusion occurred. Furthermore, the amount of wire Ni exceeded 1.2 mass%, the weld metal strength became too high, and the toughness deteriorated. In Comparative Example 23, the amount of Ti wire was less than 0.10% by mass and the amount of B was less than 0.008% by mass, so that the effect of refining the weld metal structure could not be obtained and the toughness deteriorated. In Comparative Example 24, the amount of F in the slag forming agent of the wire exceeded 0.7% by mass and melted down during welding. In Comparative Example 25, the Mn content of the wire was less than 1.8% by mass, and the desired strength was not obtained. In Comparative Example 26, the amount of Ni in the wire was less than 0.9% by mass, and the toughness deteriorated. In Comparative Example 27, the amount of Mg in the wire was less than 0.15% by mass, and the toughness deteriorated. In Comparative Example 28, the amount of Mg in the wire exceeded 0.30% by mass, and sputtering occurred frequently.

It is a figure which shows the welding method.

Explanation of symbols

1: welded plate 2: sliding copper plate 3: backing material 4: shield gas supply unit 5: weld metal 6: molten slag and molten pool 7: electrode 8: pipe 9: slag relief groove

Claims (2)

A pair of welded plates each having a groove whose front side is wider than the rear side are arranged so that the groove extends in the vertical direction, and the surface side of the welded plate is relatively to the welded plate. A sliding copper plate that slides upward is applied, a backing material fixed to the welded plate is applied to the back side of the welded plate, and the inside of the groove is vertically butt-matched by one-electrode electrogas arc welding. In the flux-cored wire used for welding, C: 0.03 to 0.07 mass% per total mass of the wire,
Si: 0.3 to 0.6% by mass,
Mn: 1.8 to 2.0% by mass,
Ni: 0.9 to 1.2% by mass,
Mo: 0.3 to 0.8 mass%,
Ti: 0.10 to 0.27% by mass,
B: 0.008 to 0.014% by mass,
Mg: 0.15 to 0.30 mass%,
Slag generating agent: 1.0 to 2.0% by mass,
F: 0.4 to 0.7% by mass of the slag forming agent (F converted value per wire total mass),
Containing
Cr: 0.1% by mass or less,
Cu: 0.3 mass% or less,
Al: 0.05% by mass or less,
P: 0.025 mass% or less,
S: 0.025 mass% or less,
A flux-cored wire for electrogas arc welding, characterized in that _{2. The} flux-cored wire for electrogas arc welding according to claim 1, comprising CO ₂ : 0.10 to 0.25 mass% per total mass of the wire.

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