JP6437378B2 - Flux-cored wire for gas shielded arc welding - Google Patents

Description

  The present invention relates to a flux-cored wire for gas shielded arc welding of 490 to 550 MPa class steel, and is particularly excellent in welding workability when performing high current welding, and also under welding conditions of high heat input and high pass temperature. The present invention relates to a flux-cored wire for gas shielded arc welding capable of obtaining a weld metal having excellent mechanical performance.

  In the field of building steel frames, gas shielded arc welding in a high current region using a solid wire for welding has been conventionally performed in order to improve the efficiency of welding construction. High current welding using solid wire for welding can increase the amount of welding per layer, so it is possible to increase the efficiency of welding, but the arc is unstable and the amount of spatter generated is large. There is a problem that welding workability is poor such as a poor shape. In addition, high current welding using a solid wire for welding has a problem in that spatter becomes large and removal of the spatter adhering to the surface of the steel sheet becomes difficult, resulting in poor work efficiency.

  As means for solving these problems, development of a solid wire for gas shielded arc welding with a small amount of spatter has already been made. For example, Patent Document 1 discloses that a suitable amount of a supply lubricant composed of molybdenum disulfide, phospholipid, and a lubricant that is liquid at room temperature is attached to the surface of the wire to improve wire feedability, and the amount of spatter generated during welding is reduced. Techniques for reducing are disclosed. Patent Document 2 discloses a welding solid wire that can reduce the amount of spatter generated by forming an alkali metal impregnated portion impregnated with two or more kinds of alkali metals under the surface of the wire. However, high current welding using solid wire for welding generates a lot of spatter itself, so even if the wire feedability is improved, the spatter generation amount cannot be reduced sufficiently, and the bead appearance and shape are also improved. There was a problem that could not be done.

  In recent years, solid wire for gas shielded arc welding has been developed to meet the welding conditions of high heat input and high-pass temperature for the purpose of further improving the efficiency of welding. It is defined in JIS Z3312 YGW18. Such a solid wire for gas shielded arc welding has a maximum heat input of 40 kJ with respect to a high-strength steel having a tensile strength of 490 MPa class as a condition capable of welding without causing a decrease in the strength and toughness of the weld metal. / Cm and a welding condition of a maximum pass temperature of 350 ° C. are allowed. For high-tensile steel with a tensile strength of 520 MPa, welding conditions with a maximum heat input of 30 kJ / cm and a maximum interpass temperature of 250 ° C. are allowed.

  The solid wire for gas shielded arc welding corresponding to the welding conditions of large heat input and high-pass temperature includes, for example, those containing a lot of Mo, Cr, etc. in the wire, as described in Patent Documents 3-5. Proposed. According to these solid wires, it is possible to ensure the strength and toughness of the weld metal even under welding conditions of high heat input and high pass temperature, but the arc is unstable and the amount of spatter is large. There was a problem that welding workability was poor, such as the bead appearance and shape being bad.

  For example, Patent Documents 6 and 7 disclose a large heat input as a gas shielded arc welding wire that has good welding workability while ensuring the strength and toughness of the weld metal under the welding conditions of large heat input and high pass temperature. A flux-cored wire is disclosed in which good welding workability can be obtained and welding metal excellent in mechanical performance can be obtained under welding conditions with a high interpass temperature. However, with these flux-cored wires, although the spatter generation amount can be relatively reduced as compared with the high current welding with the welding solid wire, the spatter generation amount is generally large and the slag generation amount increases. There has been a problem that welding defects such as entrainment are likely to occur.

JP 2006-95551 A JP 2009-255142 A JP-A-10-230387 Japanese Patent Laid-Open No. 11-90678 JP 2001-287086 A JP 2005-279683 A JP 2011-25298 A

  Therefore, the present invention has been devised to solve the above-described problems, and the amount of spatter generated by high current welding of 490 to 550 MPa class steel is small, and the stability of the arc and the bead appearance and shape are good. Excellent in welding workability with few welding defects such as slag entrainment, and with flux for gas shielded arc welding that provides weld metal with appropriate strength and toughness under welding conditions of high heat input and high pass temperature The object is to provide a wire.

  In order to solve the above-mentioned problems, the present inventors have developed a weld metal having appropriate strength and toughness in high-current welding of 490 to 550 MPa class steel, and further in gas shielded arc welding at a high heat input / high pass temperature. About the component composition of flux-cored wire for gas shielded arc welding that provides good welding workability such as stable arc, low spatter generation, good bead appearance and shape, and prevention of welding defects We examined in detail.

As a result, under the welding conditions for high current welding, the stability of the arc and the reduction in the amount of spatter are reduced by the Na ₂ O equivalent value of the Na compound and K compound and the total amount of the K ₂ O equivalent value and F of the fluorine compound. It has been found that the bead appearance and shape are improved by making the total amount of the converted values appropriate and by containing an appropriate amount of SiO ₂ .

  In addition, in order to achieve the improvement of stable toughness at the same time as the appropriate strength of the weld metal under the welding conditions under a large current, the oxide as the slag forming agent in the wire is reduced as much as possible, and the alloy component C It has been found that it is effective to optimize the contents of Si, Mn, Cu, Ti, and Al.

  Furthermore, it is also found that by optimizing the amount of Mo and B in the wire, it is possible to further improve the toughness and increase the strength of the weld metal even under welding conditions of high heat input and high pass temperature. did.

That is, the gist of the present invention is that, in a flux-cored wire for gas shielded arc welding in which a steel outer shell is filled with a flux, the mass% with respect to the total mass of the wire, and the total of the steel outer shell and the flux, C: 0.05 -0.18%, Si: 0.4-1.60%, Mn: 1.5-2.5%, Cu: 0.05-0.5%, Ti: 0.1-0.3% Al: 0.01% or less, and further in a mass% with respect to the total mass of the wire, in the flux, 0.01 to 0.1% in total of fluorine compound: F conversion value, SiO ₂ : 0. 01-0.2%, Na compound and K compound: Containing 0.02-0.15% in total of Na ₂ O converted value and K ₂ O converted value, the balance being steel outer shell Fe, component adjustment iron powder to be added for, characterized by comprising the Fe content and unavoidable impurities iron alloy powder

  Further, the gist of the present invention is, in addition to the above-described configuration, mass% with respect to the total mass of the wire, and the total of the steel outer sheath and the flux, Mo: 0.15-0.5%, B: 0.0015-0. The flux-cored wire for gas shielded arc welding is also characterized by containing 010%.

  According to the flux-cored wire for gas shielded arc welding according to the present invention having the above-described configuration, in high-current welding, the arc stability and bead appearance / shape are excellent, the spatter generation amount is small, the slag amount is small, and the welding defect The welding workability is good, for example, and the strength and toughness of the weld metal can be sufficiently ensured even under the welding conditions of high heat input and high pass temperature, and a high quality weld metal can be obtained.

  The flux-cored wire for gas shielded arc welding according to the present invention can be achieved by a synergistic effect of each component composition individually and coexisting. The reasons for limitation of each component composition will be described below. In addition, the content rate of each component composition shall be represented by the mass% with respect to the total mass of a flux-cored wire, and the description regarding the mass% will be represented as simply%.

[C: 0.05 to 0.18% in total of steel outer shell and flux]
C is an element necessary for improving the strength of the weld metal by solid solution strengthening. If C is less than 0.05%, the desired strength of the weld metal cannot be obtained under welding conditions with a large current. On the other hand, if C exceeds 0.18%, the strength of the weld metal becomes excessively high, the toughness is lowered, and the hot cracking sensitivity is increased. Therefore, C is 0.05 to 0.18% in total of the steel outer shell and the flux. C can be added from a flux, a metal powder, an alloy powder, or the like, in addition to the components contained in the steel outer shell.

[The total amount of steel shell and flux is Si: 0.4 to 1.60 %]
Si is added to deoxidize the weld metal and ensure the strength of the weld metal. Under the welding conditions with a large current, the consumption of Si is large, but it is necessary to secure the strength by yielding an appropriate amount of Si to the weld metal. When Si is less than 0.4%, the weld metal is insufficiently deoxidized, and the strength and toughness of the weld metal are reduced under welding conditions with a large current. On the other hand, when Si exceeds 1.60 %, the strength of the weld metal becomes excessively high and toughness cannot be stably obtained. In addition, the amount of slag generated during welding increases, and welding defects such as slag entrainment tend to occur. Therefore, Si is 0.4 to 1.60 % in total of the steel outer shell and the flux. Si can be added from an alloy powder such as metal Si, Fe-Si, Fe-Si-Mn, etc. from a flux in addition to the components contained in the steel outer shell.

[Mn: 1.5 to 2.5% in total of steel outer shell and flux]
Mn is added to ensure the toughness and improve the strength of the weld metal. If Mn is less than 1.5%, the consumption of Mn increases under welding conditions with a large current, the strength of the weld metal is low, and sufficient toughness cannot be ensured. On the other hand, if Mn exceeds 2.5%, the toughness of the weld metal cannot be obtained stably. In addition, the amount of generated slag increases and welding defects such as slag entrainment tend to occur. Therefore, Mn is 1.5 to 2.5 % in total of the steel outer shell and the flux. In addition, Mn can be added from alloy powders such as metal Mn, Fe—Mn, and Fe—Si—Mn from the flux in addition to the components contained in the steel outer sheath.

[Cu total of steel outer shell and flux: 0.05 to 0.5%]
Cu has a precipitation strengthening action, lowers the transformation temperature, refines the structure of the weld metal, and stabilizes toughness. When Cu is less than 0.05%, stable weld metal toughness cannot be obtained under welding conditions with a large current. On the other hand, if Cu exceeds 0.5%, precipitation embrittlement occurs, the toughness of the weld metal decreases, and high-temperature cracking tends to occur. Therefore, Cu is made 0.05 to 0.5% in total of the steel outer shell and the flux. Cu can be added from alloy powder such as metal Cu, Fe-Si-Cu, etc. from the flux, in addition to the components contained in the steel outer shell and the Cu plating applied to the surface of the steel outer shell.

[Ti: 0.1 to 0.3% in total of steel shell and flux]
Ti acts as a deoxidizer and generates a fine oxide of Ti in the weld metal to further improve the toughness of the weld metal. When Ti is less than 0.1%, the toughness of the weld metal decreases under welding conditions with a large current. On the other hand, if Ti exceeds 0.3%, the solid solution Ti in the weld metal increases and the toughness decreases. Therefore, Ti is 0.1 to 0.3% in total of the steel outer shell and the flux. Ti can be added from alloy powder such as metal Ti, Fe-Ti, etc. from the flux in addition to the components contained in the steel outer shell.

[The total of steel outer shell and flux is Al: 0.01% or less]
If Al exceeds 0.01%, it remains as an oxide in the weld metal, and the toughness of the weld metal is reduced. If Al exceeds 0.01%, the arc becomes unstable and the amount of spatter generated increases. Therefore, the Al content is 0.01% or less in total of the steel outer shell and the flux. Al is not an essential component, and the content may be 0%.

[Fluorine compounds contained in flux: Total of F conversion values: 0.01 to 0.1%]
Fluorine compounds have the effect of concentrating and stabilizing the arc. If the total F converted value of the fluorine compound is less than 0.01%, this effect cannot be obtained, the arc is unstable, and the amount of spatter generated increases. On the other hand, if the total F converted value of the fluorine compound exceeds 0.1%, the arc becomes rough and unstable, and the amount of spatter generated increases. Therefore, the total F converted value of the fluorine compound contained in the flux is set to 0.01 to 0.1%. The fluorine compound can be added from CaF ₂ , NaF, LiF, MgF ₂ , K ₂ SiF ₆ , Na ₃ AlF ₆ , AlF _3, etc. from the flux, and the F conversion value is the total amount of F contained in them. is there.

[SiO ₂ contained in flux: 0.01 to 0.2%]
The SiO ₂ in the flux increases the viscosity of the molten slag and improves the slag encapsulation property under the welding conditions with a large current to improve the conformity of the bead toe and the bead appearance and shape. When the SiO ₂ content is less than 0.01%, the familiarity of the bead toe portion of the weld bead is deteriorated, and the bead appearance and shape are deteriorated. On the other hand, if SiO ₂ exceeds 0.2%, the amount of oxygen in the weld metal increases and the toughness decreases. In addition, the amount of slag increases and welding defects such as slag entrainment tend to occur. Thus, SiO ₂ contained in the flux is 0.01 to 0.2%. Incidentally, SiO ₂ may be added silica sand, from the solid matter component, such as water glass consisting of sodium silicate and potassium silicate from the flux.

[0.02 to 0.15% in total of Na ₂ O converted value and K ₂ O converted value of Na compound and K compound contained in flux]
Na and K compounds soften and stabilize the arc. When the total of Na ₂ O converted values and K ₂ O converted values of the Na compound and K compound is less than 0.02%, the arc becomes unstable and the amount of spatter generated increases. On the other hand, when the total of Na ₂ O converted value and K ₂ O converted value of Na compound and K compound exceeds 0.15%, the arc becomes too strong and the amount of spatter generated increases. On the other hand, if the total of the Na ₂ O converted value and the K ₂ O converted value exceeds 0.15%, the familiarity of the bead toe portion becomes worse and the bead appearance and shape become poor. Furthermore, the amount of generated slag increases, and welding defects such as slag entrainment tend to occur. Therefore, the total of Na ₂ O equivalent value and K ₂ O equivalent value of Na compound and K compound contained in the flux is 0.02 to 0.15%. Incidentally, Na compounds and K compounds may be added from sodium silicate and solid matter components of water glass consisting of potassium _{silicate, K 2 SiO 3, Na 2} SiO 3, NaF, powders such K ₂ SiF _6.

[Mo is 0.15 to 0.5% in total of steel outer shell and flux]
Mo is an important element for securing the strength of the weld metal under welding conditions of high heat input and high pass temperature. If Mo is less than 0.15%, these effects cannot be sufficiently obtained, and the required strength of the weld metal cannot be obtained under the welding conditions at high heat input and high pass temperature. On the other hand, if Mo exceeds 0.5%, the strength of the weld metal becomes excessively high and toughness cannot be stably obtained. Therefore, Mo is 0.15 to 0.5% in total of the steel outer shell and the flux. In addition, Mo can be added from the metal Mo powder from a flux other than the component contained in steel outer skin.

[B: 0.0015 to 0.010% in total of steel outer shell and flux]
B refines the structure of the weld metal under the welding conditions under high heat input and high pass temperature to improve toughness. If B is less than 0.0015%, the effect cannot be obtained, and the toughness of the weld metal is lowered under welding conditions at a high heat input and a high pass temperature. On the other hand, if B exceeds 0.010%, the strength of the weld metal becomes excessively high, and the grain boundaries become brittle, resulting in a decrease in toughness. Therefore, B is 0.0015 to 0.010% in total of the steel outer shell and the flux. B can be added from alloy powders such as Fe-Si-B and Fe-Mn-B in addition to the components contained in the steel outer sheath.

  The flux-cored wire for gas shielded arc welding according to the present invention has a structure in which a steel outer shell is formed into a pipe shape and the inside thereof is filled with flux. There are two types of wire: a seamless wire in the steel skin obtained by welding the seam of the molded steel skin, and a seam in the steel skin that is left unwelded to the steel skin. It can be roughly divided into wires. In the present invention, a wire having any cross-sectional structure can be used. However, a wire having a seam in a steel outer shell tends to cause cold cracking when the strength of the weld metal is increased. It is necessary to use it. On the other hand, a wire with a seamless steel outer sheath can be heat-treated for the purpose of reducing the total amount of hydrogen in the wire, and since there is no moisture absorption of the flux after production, the amount of diffusible hydrogen in the weld metal This is more preferable because it is possible to improve the cold cracking resistance.

  The balance of the flux-cored wire for gas shielded arc welding of the present invention is Fe of steel outer sheath, Fe of iron alloy powder such as Fe powder, Fe-Si, Fe-Mn, Fe-Ti alloy added for component adjustment. Minute and inevitable impurities.

  Moreover, although a flux filling rate is not specifically limited, It is preferable to set it as 8 to 20% with respect to the total wire mass from a viewpoint of productivity.

  The shield gas is carbon dioxide gas, and the flow rate of the shield gas is preferably 20 to 35 liters / minute in order to prevent defect resistance and nitrogen contamination from the atmosphere.

  Hereinafter, the effect of the present invention will be described in detail with reference to examples.

  After using SPCC defined in JIS G3141 as a steel outer shell (C: 0.01 to 0.05%) and forming the steel outer shell into a U-shape, the joint of the steel outer shell is formed. A welded seamless wire was piped and drawn, and flux-cored wires having various components shown in Table 1 were made as trial products. The wire diameter was 1.4 mm.

  Using the prototyped flux-cored wires shown in Table 1, the welding workability, the amount of spatter generation, the presence or absence of welding defects, and the weld metal performance were investigated.

  The welding workability and the weld metal performance are shown in Condition No. Under the T1 construction conditions, a multi-layer weld metal test was conducted on a groove with a 35 ° gap and a root gap of 8 mm. The survey items were the arc stability during welding and the bead appearance and shape. In addition, the wire supply at the time of welding used the conduit cable of 6m length. After the welding was completed, the backing metal was deleted and an X-ray transmission test was performed. Moreover, the A0 tensile test piece and the impact test were sampled from the weld metal part to investigate the mechanical performance.

  Tensile strength was 490 MPa or more, and toughness was evaluated by conducting five Charpy impact tests at 0 ° C., and the average absorbed energy was 80 J or more, and the minimum value was 60 J or more.

  The amount of spatter generated was determined using the copper collection box under the conditions No. 1 shown in Table 2. Bead-on-plate welding was repeated 30 seconds × 5 times under T2 welding conditions, and the amount of spatter generated per minute was calculated. The amount of spatter generated per minute was set to 1.5 g or less. The results are summarized in Table 3.

The wire symbols 1 to 10 in Tables 1 and 3 are examples of the present invention, and the wire symbols 11 to 22 are comparative examples. Wire symbols 1 to 10 which are examples of the present invention have an appropriate content of C, Si, Mn, Cu, Ti and Al in the flux-cored wire, and a total of F converted values of fluorine compounds in the flux, SiO ₂ , Since the total of Na ₂ O converted value and K ₂ O converted value of Na compound and K compound is an appropriate amount, the arc is stable and the bead appearance and shape are good even under large current welding conditions. There were few weld defects, and the average value and minimum value of the tensile strength and absorbed energy of the weld metal were both good and very satisfactory.

  In the comparative example, since the wire symbol 11 has a small amount of C, the tensile strength of the weld metal was low. Further, since the total of F converted values of the fluorine compound is small, the arc is unstable and the amount of spatter generated is large.

Since the wire symbol 12 has a lot of C, the tensile strength of the weld metal was high and the absorbed energy was low. Moreover, the crater part cracked. Further, since the total F converted value of the fluorine compound is large, the arc is rough and unstable, and the amount of spatter generated is large.

Since the wire symbol 13 has little Si, the tensile strength of the weld metal was low and the absorbed energy was also low. In addition, since the SiO ₂ is small, bead appearance and shape was poor.

Since the wire symbol 14 has a large amount of Si, the tensile strength of the weld metal was high and the minimum value of absorbed energy was low. Moreover, since the amount of slag generation increased, a slag entrainment defect occurred. Further, since the total of Na ₂ O converted value and K ₂ O converted value of Na compound and K compound was large, the arc was strong, the amount of spatter was large, and the bead appearance and shape were also poor.

  Since the wire symbol 15 has a small amount of Mn, the tensile strength of the weld metal was low and the absorbed energy was also low.

Since the wire symbol 16 has a large amount of Mn, the minimum value of the absorbed energy of the weld metal is low, and the amount of slag generated is large, so that a slag entrainment defect occurs. Further, since the total of Na ₂ O converted value and K ₂ O converted value of Na compound and K compound was small, the arc was unstable and the amount of spatter was large.

  Since the wire symbol 17 has a small amount of Cu, the minimum value of the absorbed energy of the weld metal was low.

  Since the wire symbol 18 has a large amount of Cu, the absorbed energy of the weld metal was low. Moreover, the crater part cracked.

  Since the wire symbol 19 has a small amount of Ti, the absorbed energy of the weld metal was low.

  Since the wire symbol 20 has a large amount of Ti, the absorbed energy of the weld metal was low.

  Since the wire symbol 21 has a large amount of Al, the arc was unstable and the amount of spatter generated was large. Moreover, the absorbed energy of the weld metal was low.

Since the wire symbol 22 has a large amount of SiO ₂ , the absorbed energy of the weld metal was low. Moreover, since the amount of slag generation increased, a slag entrainment defect occurred.

  As in Example 1, SPCC defined in JIS G3141 was used as a steel outer shell (C: 0.04%), and after forming into a U-shape in the process of forming the steel outer shell, the steel outer shell was assembled. A seamless wire with welded eyes was piped and drawn to produce flux-cored wires of various components shown in Table 4. The wire diameter was 1.4 mm.

  Using the experimentally prepared flux-cored wires shown in Table 4, the welding workability, the amount of spatter generation, and the weld metal performance were investigated.

  The welding workability and the weld metal performance are shown in Condition No. A multi-layer weld metal test was conducted on a groove with a backing metal with a 35 ° groove and a root gap of 8 mm under the construction conditions of large heat input and high pass temperature of T3. The investigation items were the same as in Example 1, and the arc stability during welding and the bead appearance / shape were investigated. After the welding was completed, the backing metal was deleted and an X-ray transmission test was performed. Further, A0 tensile test pieces and impact tests were taken from the weld metal part to investigate the mechanical performance.

  Tensile strength was 520 MPa or more, and toughness was evaluated by conducting five Charpy impact tests at 0 ° C., and the average value of absorbed energy was 80 J or more, and the minimum value was 60 J or more.

  As the amount of spatter generated, the amount of spatter generated per minute was calculated using the same collection method as in Example 1. The amount of spatter generated per minute was set to 1.5 g or less. The results are summarized in Table 5.

The wire symbols 23 to 26 in Tables 4 and 5 are examples of the present invention, and the wire symbols 27 to 30 are comparative examples. In the wire symbols 23 to 26 of the present invention, C, Si, Mn, Cu, Ti, Al, Mo and B in the flux-cored wire are appropriate, and the total of F converted values of the fluorine compounds in the flux is SiO _2. Since the total of Na ₂ K converted value and K ₂ O converted value of Na and K compounds is appropriate, the arc is stable and the bead appearance and shape are good even under welding conditions with high heat input and high pass temperature Thus, the spatter generation amount was small, there were no welding defects, and the average value and the minimum value of the tensile strength and absorbed energy of the weld metal were both good and very satisfactory.

  Since the wire symbol 27 in the comparative example has a small amount of Mo, the tensile strength of the weld metal was low.

  Since the wire symbol 28 has a large amount of Mo, the tensile strength of the weld metal was high and the minimum value of absorbed energy was low.

  Since the wire symbol 29 has a small amount of B, the absorbed energy of the weld metal was low.

  Since the wire symbol 30 has a large amount of B, the tensile strength of the weld metal was high and the absorbed energy was low.

  In addition, although the wire symbols 27 to 30 as these comparative examples are certainly inferior in tensile strength and absorbed energy of the weld metal to the wire symbols 23 to 26, the welding workability is good. The result of the X-ray transmission test was also good. For this reason, the wire symbols 27-30 as these comparative examples are also included in the scope of the present invention.

Claims (2)

In the flux-cored wire for gas shield arc welding, which is formed by filling the steel outer shell with flux,
It is the mass% with respect to the total mass of the wire.
C: 0.05 to 0.18%,
Si: 0.4 to 1.60%,
Mn: 1.5 to 2.5%
Cu: 0.05 to 0.5%,
Ti: 0.1 to 0.3% is contained,
Al: 0.01% or less,
Furthermore, in the flux in mass% with respect to the total mass of the wire,
Fluorine compound: 0.01 to 0.1% in total in terms of F,
SiO ₂ : 0.01 to 0.2%,
Na compound and K compound: 0.02 to 0.15% in total of Na ₂ O converted value and K ₂ O converted value,
A flux-cored wire for gas shielded arc welding, wherein the balance is made of Fe of steel outer sheath, iron powder added for component adjustment, Fe content of iron alloy powder, and inevitable impurities. It is the mass% with respect to the total mass of the wire.
Mo: 0.15-0.5%,
B: The flux cored wire for gas shielded arc welding according to claim 1, further comprising 0.0015 to 0.010%.