JP5952597B2 - 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.

Conventionally, gas shield arc welding using a flux-cored wire has been performed in various fields in order to perform the welding operation with high efficiency. In all-position welding, a titania-based flux-cored wire (for example, refer to Patent Document 1) having good welding workability and bead shape is often used. Each industry that uses a lot of such welding materials is constantly working to improve the efficiency of welding work in order to further reduce costs and shorten delivery times.
For such an approach, a technique for improving the slag peelability by preventing seizure of the slag has been disclosed (see, for example, Patent Document 2).

JP S56-39193 JP S57-190798

  However, in the standing improvement advance welding in the high current region using the flux-cored wire as described in Patent Document 2, there is a problem that the weld metal tends to sag and it is difficult to maintain a good bead shape. In addition to the formation of a good bead shape, improvement in welding workability such as improvement in arc stability and reduction in the amount of fume and spatter is desired.

  The present invention has been made in view of the above problems, and is a flux-cored wire for gas shielded arc welding capable of forming a good bead by vertical advance welding while maintaining good welding workability even at a high current. It is an issue to provide.

The flux-cored wire for gas shielded arc welding according to the present invention (hereinafter, appropriately referred to as flux-cored wire or FCW or simply wire) is a flux-cored wire for gas shielded arc welding, and is in the form of particles per total mass of the wire. Titanium oxide raw material comprising: 5.0 to 9.0% by mass, C: 0.02 to 0.11% by mass, the sum of the Si equivalent amount of metal Si and the Si equivalent amount of Si oxide: 0.3 to 1.2% by mass, Si equivalent of metal Si: 0.2% by mass or more, Mn: 1.0 to 3.0% by mass, total of Al equivalent of metal Al and Mg: 0.1 to 1. 0% by mass, total of Na equivalent in Na compound and K equivalent in K compound: 0.05 to 1.50% by mass, F equivalent in F compound: 0.02 to 0.85% by mass containing the balance be Fe and unavoidable impurities Flux filling rate per total mass of the wire is 10 to 25 wt%, the titanium oxide raw material, the titanium oxide material total _mass, TiO 2: 58.0-99.0 wt%, Si: 2.5 wt% Hereafter, the composition which is Al: 3.0 mass% or less, Mn: 5.0 mass% or less, Fe: 35.0 mass% or less, Mg: 5.0 mass% or less, Ca: 2.0 mass% or less And an oxide composed of at least one of Ti, Fe, Mn, Al, and Si is present on the particle surface of the titanium oxide raw material, and the oxide has an atomic percentage of Al and Si. Satisfies 1 ≦ Al + Si ≦ 10 (however, the wire component other than the titanium oxide raw material excludes the component contained in the titanium oxide raw material).

  According to such a configuration, in the component of the flux-cored wire, by defining the titanium oxide raw material and the amount of Si, the welding workability of the vertical improvement is improved, and by specifying the amounts of C, Mn, Al, and Mg, the toughness Will improve. Also, by regulating the amount of Na and K, arc droplet transfer during welding is stabilized, and by defining the amount of F, the hydrogen partial pressure in the welding atmosphere is reduced, and the amount of diffusible hydrogen in the weld metal is reduced. Go down. Furthermore, by defining the flux filling rate, the productivity is not deteriorated, the arc stability is not deteriorated, and the spatter generation amount is suppressed.

In addition, by defining the amount of TiO ₂ in the component of the titanium oxide raw material, the bead shape is improved, and by containing the amounts of Si, Al, and Mn, the viscosity of the slag is adjusted.
Further, by defining the amount of Fe, a decrease in melting point is suppressed, and by defining the amounts of Mg and Ca, the amount of spatter generated is suppressed. Furthermore, by defining the atomic percentages of Al and Si, the melting point of the titanium oxide raw material becomes appropriate, and the bead shape becomes good.

  The flux-cored wire for gas shielded arc welding according to the present invention further contains B: 0.0003 to 0.0130 mass%, Ni: 0.1 to 1.0 mass%, and Cr: It is characterized by being suppressed to 0.20 mass% or less, Nb: 0.05 mass% or less, and V: 0.05 mass% or less.

  According to such a configuration, the low temperature toughness at −40 ° C. is improved by adding a predetermined amount of B and Ni and suppressing the content of Cr, Nb, and V to a predetermined amount.

  In the flux-cored wire for gas shielded arc welding according to the present invention, the Ti equivalent amount of metal Ti: 0.05 to 0.40 mass%, B: 0.0003 to 0.0150 mass%, based on the total mass of the wire. Ni: 0.3 to 3.0% by mass, Cr: 0.20% by mass or less, Nb: 0.05% by mass or less, V: 0.05% by mass or less are suppressed.

  According to such a configuration, a predetermined amount of B and Ni are added, the content of Cr, Nb and V is suppressed to a predetermined amount, and furthermore, a predetermined amount of metal Ti is added, even at an extremely low temperature of −60 ° C. It is possible to ensure toughness.

  The flux-cored wire for gas shielded arc welding according to the present invention further contains Ni: 0.3 to 3.0% by mass, Mo: 0.01 to 0.50% by mass, and Nb: It is characterized by being suppressed to 0.05 mass% or less and V: 0.05 mass% or less.

  According to such a configuration, a flux-cored wire with improved strength is obtained by adding a predetermined amount of Ni and Mo and suppressing the Nb and V contents to a predetermined amount.

According to the present invention, good workability can be maintained even at a high current, and a good bead can be formed by vertical welding. Furthermore, by adjusting the content of the predetermined element, a weld metal having good mechanical properties can be formed even if heat input increases due to high current butt welding.
Further, as another form, by adjusting the content of the predetermined element, it is possible to achieve stabilization of toughness by large heat input construction, securing toughness at extremely low temperature, and improvement of strength.

It is a figure which shows the bead shape and conformity evaluation criteria in a flux cored wire.

Hereinafter, embodiments of the present invention will be described in detail.
<< First Embodiment >>
The first embodiment relates to a mild steel flux cored wire.
The flux-cored wire for gas shielded arc welding of the present invention is a particulate titanium oxide raw material, C, the sum of the Si equivalent amount of metal Si and the Si equivalent amount of Si oxide, the Si equivalent amount of metal Si, Mn, Contains a predetermined amount of the total amount of metal Al in terms of Al and Mg, the sum of the amount of Na in the Na compound and the amount of K in the K compound, and the amount of F in the F compound. Further, the flux filling rate per total mass of the wire is a predetermined amount.

Further, the titanium oxide raw material has a composition in which a predetermined amount of TiO ₂ , Si, Al, Mn, Fe, Mg, and Ca per total mass of the titanium oxide raw material, and Ti, An oxide composed of at least one of Fe, Mn, Al, and Si exists, and this oxide satisfies 1 ≦ Al + Si ≦ 10 in terms of atomic percentage of Al and Si.

Here, “metal Si” means one or more of “pure metal Si” and “alloy Si”. Similarly, “metal Al” means one or more of “pure metal Al” and “alloy Al”. For example, when simply written as Mg, it is a converted amount of Mg including pure metals, alloys, compounds, and all other Mg.
“Oxide” means one or more of “single oxide” and “composite oxide”. “Single oxide” means, for example, an oxide of Ti alone (TiO ₂ ) if it is Ti, and “composite oxide” means a collection of a plurality of these single oxides, for example, It refers to both oxides containing a plurality of metal components such as Ti, Fe, and Mn. And the state that this oxide exists in the surface of the particle | grains of a titanium oxide raw material includes the case where the surface of particle | grains is an oxide state.

  Hereinafter, the reasons for limiting the components of the flux-cored wire of the present invention and the reasons for limiting the components of the titanium oxide raw material will be described.

[Reason for limiting the components of flux-cored wire]
<Titanium oxide raw material: 5.0 to 9.0% by mass>
By using a titanium oxide raw material having an optimized oxide composition as will be described later as a TiO ₂ source, it is possible to have good standing improvement welding workability. If the content of the titanium oxide raw material per the total mass of the wire is less than 5.0% by mass, the stand-up improvement progress is deteriorated and a good bead shape cannot be secured. On the other hand, if it exceeds 9.0% by mass, the melting point of the slag becomes high, and the slag hardens quickly when weaving is performed by vertical welding. As a result, a weld metal is formed along the carrying rod, resulting in a scale bead. Therefore, the content of the titanium oxide raw material is 5.0 to 9.0% by mass. More preferably, it is 6.0-8.0 mass%. Within this range, the bead shape is further improved.

<C: 0.02-0.11 mass%>
C is a hardenable element and has the effect of improving toughness. If the C content per total mass of the wire is less than 0.02% by mass, the weld metal is insufficiently quenched and it is difficult to ensure sufficient mechanical properties. On the other hand, if it exceeds 0.11% by mass, the arc is strongly blown, and the base material is dug by the arc force at the time of vertical welding, causing a bead shape defect. Therefore, the C content is 0.02 to 0.11% by mass. More preferably, it is 0.03-0.10 mass%.

<Total of Si conversion amount of metal Si and Si conversion amount of Si oxide: 0.3 to 1.2% by mass>
Si improves the viscosity of the weld metal and improves the workability of the welding process. If the total amount of metal Si equivalent per total mass of wire and Si equivalent in Si oxide is less than 0.3% by mass, the weld metal viscosity decreases and the bead shape of vertical improvement welding deteriorates. To do. On the other hand, if it exceeds 1.2% by mass, it is a low melting point element, which causes deterioration of hot cracking resistance. Moreover, precipitation of grain boundary ferrite is promoted, and toughness is deteriorated. Therefore, the total amount of the Si equivalent of metal Si and the Si equivalent of Si oxide is 0.3 to 1.2% by mass. More preferably, it is 0.8 mass% or more. As will be described later, since the Si equivalent amount of metal Si is 0.2% by mass or more, if the Si equivalent amount of metal Si is 0.3 to 1.2% by mass, the Si oxide Si The converted amount may be 0% by mass.
In addition, although both metal Si and Si oxide improve the stand-up improvement progress, the role of an effect | action differs. That is, the metal Si increases the weld metal viscosity during welding and makes the weld metal difficult to sag. The oxide covers the weld metal with slag and has an effect of preventing the weld metal from dripping.

<Si equivalent amount of metal Si: 0.2 mass% or more>
As described above, Si improves the viscosity of the weld metal and improves the welding workability of the vertical improvement. When the Si-converted amount of metal Si per total mass of the wire is less than 0.2% by mass, the weld metal viscosity is lowered, and the bead shape of vertical improvement welding is degraded. Therefore, the Si equivalent amount of metal Si is 0.2 mass% or more. More preferably, it is 0.4 mass% or more. In addition, a preferable upper limit is 1.2 mass%.

<Mn: 1.0 to 3.0% by mass>
Mn is a hardenability element and has the effect of improving toughness. If the Mn content per the total mass of the wire is less than 1.0% by mass, the weld metal is insufficiently quenched and it is difficult to ensure sufficient mechanical properties. On the other hand, if it exceeds 3.0 mass%, the strength of the welded portion becomes excessive and the toughness becomes insufficient. Therefore, the Mn content is 1.0 to 3.0% by mass.
As the Mn source, metal powder such as Mn metal powder, Fe—Mn, Fe—Se—Si—Mn, and alloy powder are used, but in addition to these, Mn oxide may be added.

<Total of Al of metal Al and Mg: 0.1 to 1.0% by mass>
Metals Al and Mg are strong deoxidizing elements and have a role of reducing the oxygen content of the weld metal and improving toughness. If the total amount of Al of metal Al and Mg per the total mass of the wire is less than 0.1% by mass, the oxygen content of the weld metal is high and it is difficult to ensure sufficient mechanical properties. On the other hand, if it exceeds 1.0 mass%, an increase in spatter due to arc instability occurs and welding workability deteriorates. Therefore, the total amount of metal Al in terms of Al and Mg is 0.1 to 1.0% by mass. One of the Al equivalent amount and the Mg content of metal Al may be 0% by mass.
As the Mg source, metal powder such as metal Mg, Al—Mg, Fe—Si—Mg, alloy powder, or the like is used, but besides these, Mg oxide may be added.

<Total of Na conversion amount in Na compound and K conversion amount in K compound: 0.05 to 1.50 mass%>
Na and K have a role of stabilizing the droplet transfer of the arc during welding. When the total amount of Na converted amount and K converted amount per the total mass of the wire is less than 0.05% by mass, the transfer of arc droplets during welding is unstable and the amount of spatter generated increases. On the other hand, when it exceeds 1.50 mass%, moisture absorption resistance will deteriorate. Therefore, the total amount of the Na equivalent amount in the Na compound and the K equivalent amount in the K compound is 0.05 to 1.50 mass%. In addition, as for Na conversion amount in Na compound and K conversion amount in K compound, either one may be 0 mass%.

<F: 0.02-0.85 mass%>
F exists as a fluorine compound in the flux. In F, the hydrogen partial pressure in the welding atmosphere decreases, and the amount of diffusible hydrogen in the weld metal decreases. If the F content per total mass of the wire is less than 0.02% by mass, the amount of diffusible hydrogen increases and cold cracks occur in the weld. On the other hand, if it exceeds 0.85 mass%, the amount of fume generation increases and the welding workability deteriorates. Therefore, the F content is 0.02 to 0.85 mass%.

<Flux filling ratio: 10 to 25% by mass>
When the flux filling rate per total mass of the wire is less than 10% by mass, the arc stability is deteriorated and the amount of spatter generated is increased, so that the welding workability is deteriorated. On the other hand, if it exceeds 25% by mass, the productivity is remarkably deteriorated, such as wire breakage or powder spilling during the flux filling. Therefore, the flux filling rate is 10 to 25% by mass.

<Balance: Fe and inevitable impurities>
The balance of the entire flux-cored wire is Fe and inevitable impurities. In addition to the wire component described above, a small amount of Ca, Li, etc. as a fine-tuning agent such as deoxidation, and Cu, Co, N as a further hardener for the weld metal are contained in the flux as the wire component. You can also. These elements do not affect the object of the present invention. Further, the flux contains a trace amount of an alkali metal compound other than the above elements.
Further, as inevitable impurities, for example, B, Ni, Mo, Cr, Nb, V, etc. are each B: less than 0.0003 mass%, Ni: less than 0.1 mass%, Mo: less than 0.01 mass% Cr: less than 0.30% by mass, Nb: less than 0.10% by mass, and V: less than 0.10% by mass. However, it is not limited to these components and numerical values.

[Raw materials for titanium oxide]
_<TiO 2: 58.0~99.0 mass%>
TiO ₂ plays an important role in supporting the weld metal. In vertical welding, if the TiO ₂ content per total mass of the titanium oxide raw material is less than 58.0% by mass, the amount of slag is insufficient and the bead shape becomes a drooping shape. On the other hand, if it exceeds 99.0% by mass, the melting point is too high and the slag hardens quickly, and the pool size during welding becomes small. For this reason, it is difficult to maintain a constant molten pool shape when weaving in vertical improvement welding, and the bead shape becomes uneven. Therefore, the TiO ₂ content is set to 58.0 to 99.0% by mass. In general, a high TiO ₂ content as a titanium oxide raw material is suitable for vertical welding because the melting point is high, and a low TiO ₂ content is suitable for fillet welding.

<Si: 2.5 mass% or less, Al: 3.0 mass% or less, Mn: 5.0 mass% or less>
Si, Al, Mn oxides (single oxide or composite oxide) and carbonates are added to adjust the viscosity of the slag. However, oxides and carbonates of Si, Al, and Mn sources are generally not used with a titanium oxide source, but in the flux by another raw material (for example, silica sand, alumina, manganese carbonate, manganese dioxide, etc.). Added. When the Si, Al, and Mn contents per total mass of the titanium oxide raw material in the titanium oxide source are increased, the mechanical performance and the slag viscosity are affected. Accordingly, the Si content is 2.5 mass% or less, the Al content is 3.0 mass% or less, and the Mn content is 5.0 mass% or less. Each may be 0% by mass, but as will be described later, the atomic percentage of Al and Si on the surface of the titanium oxide raw material particles must satisfy “1 ≦ Al + Si ≦ 10”. One or more inclusions are essential.

<Fe: 35.0 mass% or less>
As the content of Fe contained in oxides and carbonates increases, the melting point decreases, so that the molten metal tends to sag. For this reason, generally, it is preferable that the Fe content is high in the fillet welding material and the Fe content is low in the vertical improvement welding material. In order to use it as a titanium oxide source or as a raw material for both fillet welding and vertical welding, the Fe content per total mass of the titanium oxide raw material should be 35.0% by mass or less. is necessary. In addition, 0 mass% may be sufficient.

<Mg: 5.0% by mass or less, Ca: 2.0% by mass or less>
Since the titanium oxide raw material is manufactured from natural raw materials (rutile, illuminite, lucoxin), impurities such as Mg and Ca (including oxides and carbonates) are necessarily included in the titanium oxide raw material of the present invention. End up. However, since sputtering increases when there is much Mg and Ca, the Mg content per total mass of the titanium oxide raw material needs to be 5.0% by mass or less, and the Ca content needs to be 2.0% by mass or less. . Each may be 0% by mass.

  In addition, in the components of the titanium oxide raw material, for example, as inevitable impurities, C, Nb, V and the like are each C: 0.30 mass% or less, Nb: 0.30 mass% or less, V: 0.30 mass% You may contain the following. However, it is not limited to these components and numerical values.

<Oxides composed of at least one of Ti, Fe, Mn, Al, and Si exist on the particle surface of the titanium oxide raw material>
In this oxide, the atomic percentage of Al and Si satisfies “1 ≦ Al + Si ≦ 10”. More preferably, the atomic percentage of Al and Si is “1.5 ≦ Al + Si ≦ 6”. That is, it is essential that an oxide of Al or Si exists. More preferably, the atomic percentage of Ti, Fe, Mn and O is “1 <Ti / Fe + Mn ≦ 100” or “O / (Fe + Mn) ≦ 100”.

  These rules can be adjusted by, for example, the following method as described later. After the titanium oxide raw material is manufactured, oxides, carbonates, and the like of Fe, Mn, Al, Si, Mg, and Ca are added and fired (sintered) to the extent that the surface of the titanium oxide raw material is slightly melted. Although the firing temperature depends on the amount of oxygen in the titanium oxide raw material and the firing method, the firing temperature is about 800 to 1300 ° C. and is sintered together with the additive raw material in a rotary kiln or batch furnace.

  The surface state of the titanium oxide raw material particles needs to satisfy the following formulas 1 to 3 calculated from the surface analysis results according to a predetermined analysis method. In other words, in EDX (Energy Dispersive X-ray spectroscopy), a carbon tape (C tape) is attached to an aluminum base, and then a raw material (about 3 g) is installed, and the surface of the raw material at a high magnification (about 2000 times) is relatively Five particles having a flat area in which no foreign matter is present (not attached) (rectangular region of 10 μm × 10 μm) are randomly selected, and the atomic weight ratio of one field is measured for each particle. About the measurement result of the 5 points | pieces, the value of numerical formula 1-3 shown below is calculated | required and the average value of the value of numerical formula is calculated | required. By this measuring method, the titanium oxide raw material of the present invention can be evaluated.

Formula 1: (x = Al + Si)
Formula 2: (y = Ti / (Fe + Mn))
Formula 3: (z = O / (Fe + Mn))

In Formula 1, x is 1-10. The amounts of Al and Si relative to the amount of TiO ₂ affect the melting point of the titanium oxide raw material. When the value x of Formula 1 is between 1 and 10, there is no particular difference in the bead shape. However, when x exceeds 10, the melting point of the titanium oxide raw material is lowered, resulting in a convex bead at the time of vertical welding. . On the other hand, when x is lower than 1, the melting point of the titanium oxide raw material is too high, and the bead shape becomes uneven. For this reason, although x is set to 1-10, when x is 1.5-6, the familiarity of the beads is particularly good.

In Formula 2, y is preferably greater than 1 and 100 or less. The amount of Fe and Mn relative to the amount of TiO ₂ affects the melting point of the titanium oxide raw material. If the value of y is 1 or less, the Ti content is low, and the Fe and Mn content having a low melting point are increased. Therefore, the melting point of the titanium oxide raw material is lowered, the weld metal tends to sag, and a convex bead is formed. When y exceeds 100, the melting point of the titanium oxide raw material increases and the slag hardens quickly. Therefore, it becomes difficult to control the molten pool shape, resulting in a poor bead shape. For this reason, y is preferably larger than 1 and 100 or smaller.

  The value z in Equation 3 is preferably 100 or less. If z exceeds 100, the amount of oxygen in the weld metal becomes excessive and the viscosity is lowered, so that the beads are likely to sag in the vertical improvement welding and become convex beads. For this reason, z is preferably 100 or less.

<< Second Embodiment >>
The second embodiment relates to FCW corresponding to low temperature toughness. In the second embodiment, in the flux-cored wire of the first embodiment, in order to improve the low temperature toughness at −40 ° C., a predetermined amount of B and Ni is added, and the content of Cr, Nb, and V is set to a predetermined amount. Suppressed.

<B: 0.0003 to 0.0130 mass%>
B segregates at the γ grain boundary and has the effect of suppressing the formation of pro-eutectoid ferrite, which is effective in improving the toughness of the weld metal. When the B content per total mass of the wire is less than 0.0003% by mass, most of B is fixed as BN to the nitride, there is no effect of suppressing the formation of pro-eutectoid ferrite, and improvement in toughness cannot be confirmed. On the other hand, when it exceeds 0.0130 mass%, the strength of the weld metal is remarkably increased and the toughness is lowered. Therefore, the B content is set to 0.0003 to 0.0130 mass%.

<Ni: 0.1 to 1.0% by mass>
Ni has the effect of stabilizing the low temperature toughness. If the Ni content per total mass of the wire is less than 0.1% by mass, improvement in low temperature toughness cannot be confirmed. On the other hand, when it exceeds 1.0 mass%, the strength of the weld metal is remarkably increased and the toughness is lowered. Therefore, the Ni content is 0.1 to 1.0% by mass.

<Cr: 0.20 mass% or less>
Cr has the effect of improving strength. However, when the Cr content per total mass of the wire exceeds 0.20% by mass, the strength of the weld metal is remarkably increased and the toughness is lowered. Therefore, the Cr content is 0.20 mass% or less. In addition, 0 mass% may be sufficient.

<Nb: 0.05 mass% or less, V: 0.05 mass% or less>
Nb and V deteriorate toughness by segregating at the grain boundaries. In order to prevent toughness deterioration, it is necessary that the Nb and V contents per total mass of the wire be 0.05% by mass or less. Each may be 0% by mass.

«Third embodiment»
The third embodiment relates to FCW corresponding to cryogenic toughness. In the third embodiment, in the flux-cored wire of the first embodiment, a predetermined amount of B and Ni are added, the content of Cr, Nb, and V is suppressed to a predetermined amount, and further, a predetermined amount of metal Ti is added. Thus, toughness can be secured even at an extremely low temperature of −60 ° C. In addition, a predetermined amount of Mo may be contained.

<Ti conversion amount of metal Ti: 0.05 to 0.40 mass%>
Metal Ti means one or more of “pure metal Ti” and “alloy Ti”.
Ti refines crystal grains and has a deoxidizing effect, and has the effect of improving toughness. The effect cannot be confirmed if the Ti equivalent amount of metal Ti per total mass of the wire is less than 0.05% by mass. On the other hand, if it exceeds 0.40 mass%, a large amount of Ti compound such as TiC is precipitated, the strength is remarkably increased, and the toughness is decreased. Therefore, the Ti equivalent amount of metal Ti is set to 0.05 to 0.40 mass%.

<B: 0.0003 to 0.0150 mass%>
B segregates at the γ grain boundary and has the effect of suppressing the formation of pro-eutectoid ferrite, which is effective in improving the toughness of the weld metal. When the B content per total mass of the wire is less than 0.0003% by mass, most of B is fixed as BN to the nitride, there is no effect of suppressing the formation of pro-eutectoid ferrite, and improvement in toughness cannot be confirmed. On the other hand, when it exceeds 0.0150 mass%, the strength of the weld metal is remarkably increased and the toughness is lowered. Therefore, the B content is set to 0.0003 to 0.0150 mass%.

<Ni: 0.3 to 3.0% by mass>
Ni has the effect | action which strengthens the matrix in a grain, and improves the low temperature toughness of a weld metal. If the Ni content per total mass of the wire is less than 0.3% by mass, improvement in low temperature toughness cannot be confirmed. On the other hand, if it exceeds 3.0 mass%, the strength of the weld metal is remarkably increased and the toughness is lowered. Therefore, the Ni content is set to 0.3 to 3.0% by mass.

<Cr: 0.20 mass% or less>
Cr has the effect of improving strength. However, when the Cr content per total mass of the wire exceeds 0.20% by mass, the strength of the weld metal is remarkably increased and the toughness is lowered. Therefore, the Cr content is 0.20 mass% or less. In addition, 0 mass% may be sufficient.

<Nb: 0.05 mass% or less, V: 0.05 mass% or less>
Nb and V deteriorate toughness by segregating at the grain boundaries. In order to prevent toughness deterioration, it is necessary that the Nb and V contents per total mass of the wire be 0.05% by mass or less. Each may be 0% by mass.

<Mo: 0.01 to 0.50 mass%>
Mo refines the structure of the weld metal and improves the strength. If the Mo content per total mass of the wire is less than 0.01% by mass, the effect cannot be confirmed. On the other hand, when it exceeds 0.50% by mass, the strength is remarkably increased and the toughness is lowered. Therefore, the Mo content is set to 0.01 to 0.50 mass%.

<< Fourth Embodiment >>
The fourth embodiment relates to a high-strength FCW. In the fourth embodiment, in the flux-cored wire of the first embodiment, in order to improve the strength, a predetermined amount of Ni and Mo are added, and the contents of Nb and V are suppressed to a predetermined amount. In addition, a predetermined amount of Cr and metal Ti may be contained.

<Ni: 0.3 to 3.0% by mass>
Ni has the effect | action which strengthens the matrix in a grain, and improves the intensity | strength and low temperature toughness of a weld metal. If the Ni content per total mass of the wire is less than 0.3% by mass, the effect cannot be confirmed. On the other hand, when it exceeds 3.0 mass%, strength will increase remarkably and toughness will fall. In addition, cold cracks may occur in the weld. Therefore, the Ni content is set to 0.3 to 3.0% by mass.

<Mo: 0.01 to 0.50 mass%>
Mo refines the structure of the weld metal and improves the strength. If the Mo content per total mass of the wire is less than 0.01% by mass, the improvement in strength cannot be confirmed. On the other hand, when it exceeds 0.50% by mass, the strength is remarkably increased and the toughness is lowered. In addition, cold cracks may occur in the weld. Therefore, the Mo content is set to 0.01 to 0.50 mass%.

<Nb: 0.05 mass% or less, V: 0.05 mass% or less>
Nb and V deteriorate toughness by segregating at the grain boundaries. In order to prevent toughness deterioration, it is necessary that the Nb and V contents per total mass of the wire be 0.05% by mass or less. Each may be 0% by mass.

<Cr: 0.20 mass% or less>
Cr has the effect of improving strength. However, when the Cr content per total mass of the wire exceeds 0.20% by mass, the strength of the weld metal is remarkably increased and the toughness is lowered. In addition, cold cracks may occur in the weld. Therefore, the Cr content is 0.20 mass% or less.

<Ti conversion amount of metal Ti: 0.05 to 0.40 mass%>
Ti refines crystal grains and has a deoxidizing effect, and has the effect of improving toughness. The effect cannot be confirmed if the Ti equivalent amount of metal Ti per total mass of the wire is less than 0.05% by mass. On the other hand, if it exceeds 0.40 mass%, a large amount of Ti compound such as TiC is precipitated, the strength is remarkably increased, and the toughness is decreased. In addition, cold cracks may occur in the weld. Therefore, the Ti equivalent amount of metal Ti is set to 0.05 to 0.40 mass%.

Next, the manufacturing method of a titanium oxide raw material and the manufacturing method of a flux cored wire are demonstrated.
≪Titanium oxide raw material production method≫

  There are mainly two methods for producing a titanium oxide raw material: a firing method and a melting method. When the firing method is used, the Fe amount is high, and when the melting method is used, the Fe amount is low. By properly using the production method and titanium raw material, raw materials for fillet welding (higher Fe content is preferred) and vertical welding (lower Fe content is preferred) can be used separately. it can.

  First, the firing method will be described. As a raw material, natural rutile, lucoxin, and illuminite can be used as a Ti source. Ti content of each raw material is low in the order of rutile, lucoxin, and illuminite, and can be used by mixing properly according to the physical properties of the target titanium oxide raw material. In general, it is preferable to use a raw material having a high Ti content for vertical welding and a low Ti content for fillet welding. In application, since raw materials with less miscellaneous substances are used, specific gravity, magnetic force, and flotation are performed for the purpose of concentrating titanium oxide raw materials and reducing impurities. As the Si, Al, Fe, Mn, Mg, and Ca sources, Si, Al, Fe, Mn, Mg, and Ca oxides (including complex oxides) and carbonates can be used (added). Here, since the composite oxide has a low melting point compared to a single oxide and carbonate, it is advantageous for surface reaction and can be reacted at a lower temperature.

  Examples of the firing method include a rotary kiln or a batch furnace as the firing furnace. In consideration of an effective reaction between the oxidized Ti source and another oxide or carbonate, a rotary kiln in which the raw materials are uniformly contacted is preferable. In a batch furnace, when the firing temperature is 1200 ° C. or higher, there is a high possibility that the entire mixed raw material and a part thereof having a low melting point are sintered and solidified. For this reason, extra work such as coarse crushing, pulverization, and sieving of the sintered and solidified titanium oxide raw material occurs, resulting in an increase in cost. Regarding the firing atmosphere, it is considered that when the firing temperature is high, titanium nitride (melting point: 3000 ° C.), which is a nitride of titanium, is generated in the air atmosphere. Therefore, although it is encouraged that the firing atmosphere is a CO atmosphere, CO gas is easily generated by adding a C source to the firing raw material. When illuminite is used as the Ti source, in order to increase the apparent melting point of illuminite, a large amount of C source is added to reduce the Fe oxide content constituting the illuminite on the surface of the illuminite particles. That is, the composition of the surface of the illuminite particles is shifted from illuminite toward natural rutile to increase the melting point of the surface of the illuminite particles. At this time, it is not necessary to reduce to the center of the illuminite particles.

  Next, the melting method will be described. The raw material can be natural illuminite, which is low cost, as a Ti source. Also, rutile or lucoxin can be used. In application, since raw materials with less miscellaneous substances are used, specific gravity, magnetic force, and flotation are performed for the purpose of concentrating titanium oxide raw materials and reducing impurities. As the Si, Al, Fe, Mn, Mg, and Ca sources, Si, Al, Fe, Mn, Mg, and Ca oxides (including complex oxides) and carbonates can be used (added). Here, since the composite oxide has a lower melting point than the single oxide or carbonate, it is advantageous for the surface reaction and can be reacted at a lower temperature.

  As a melting method, illuminite and other raw materials (oxides, carbonates) and a deoxidizer (C source) are mixed (can be formed into pellets), and 1800 to 2000 ° C. in an arc furnace or a high frequency furnace. It can carry out by heating to. Thereby, the oxidized Fe in the illuminite is reduced to a molten state. Since Fe has a low melting point, it collects in the lower part of the furnace, and an oxide composed of Ti, Si, Al, Mn, Fe, Mg, Ca and other impurities is generated in the upper part of the furnace. In addition to an arc furnace and a high frequency furnace, an electric furnace can also be used.

  The oxide thus obtained is coarsely crushed → crushed → particle size adjusted to obtain a solvent raw material. Here, the Fe part (lower part) with a low melting point and the oxide part (upper part) with a high melting point are mixed depending on the characteristics of the welding material to be obtained (bead shape) and whether it is for vertical welding or fillet welding. Or use an intermediate layer (melting point between the upper and lower parts).

  In the case of the firing method and the melting method, C and S in the deoxidizer may remain in the titanium oxide raw material. Since these impurities adversely affect the quality of the welding material, it is necessary to carry out post-treatment (pickling or baking treatment) that differs depending on the type of impurities.

Further, in the melting method, the Ti valence (oxidation degree) in the atmosphere of the oxide is not stable. Therefore, in order to make the Ti valence the most stable tetravalence (TiO ₂ crystal structure) in the atmosphere. There are also cases where firing is performed in a CO reducing atmosphere during melting.

  If it is necessary to adjust the trace elements such as Fe, Mn, Al, Si, Mg, and Ca existing on the surface after manufacturing the titanium oxide raw material using the firing method and the melting method described above, Fe , Mn, Al, Si, Mg, Ca oxides and carbonates may be added and sintered (sintered) so that the surface of the titanium oxide raw material is slightly melted. Although the firing temperature depends on the amount of oxygen in the titanium oxide raw material and the firing method, the firing temperature is about 800 to 1300 ° C. and is sintered together with the additive raw material in a rotary kiln or batch furnace. Since Fe, Mn, Al, Si, Mg, and Ca are easily oxidized, they may be added as metals.

≪Method of manufacturing flux-cored wire≫
As an example of a method for manufacturing a flux-cored wire, first, a steel strip is formed in an open tube with a forming roll while being fed in the longitudinal direction. Next, after adding required amounts of titanium oxide raw material and metal or alloy, Fe powder, and the like to the flux so as to have a predetermined chemical composition, the cross section is processed into a circle. Thereafter, the wire diameter is set to, for example, 1.0 to 1.6 mm by cold drawing. In addition, you may anneal for the purpose of the softening of the wire hardened in the middle of cold working.

As described above, the present invention enables a flux-cored wire having improved weldability in good high-current welding by using a titanium oxide raw material with an optimized oxide composition. And, the titanium oxide raw material is controlled in the presence form of Ti, Fe, Mn, Al, Si, O on the particle surface, compatible with the appropriate melting point of slag and molten metal, viscosity and oxygen content, A good bead shape can be secured.
In addition, in order to secure the mechanical properties of butt welding by high current welding, a flux-cored wire that achieves stabilization of toughness by high heat input construction by adding B and Ni and reducing Cr, Nb, and V Make it possible. Further, by adding Ti, it becomes possible to provide a wire with a flack that achieves toughness securing even at an extremely low temperature. Moreover, the addition of Mo or the like enables a flux-cored wire that achieves securing of strength.

  Hereinafter, in order to explain the effects of the present invention, examples that fall within the scope of the present invention and comparative examples that fall outside the scope of the present invention will be compared and described.

In this example, Tables 1 and 2 are for titanium oxide raw materials, Table 3 is the result, and Table 4 is the composition of the flux wire used. In Table 1, No. corresponding to the comparative example of Table 2. 13 to 16 are described as “comparative examples”. Here, the titanium oxide raw material generally contains impurities such as Si, Al, Mn, Fe, Mg, and Ca. In Table 1, the component ranges of TiO ₂ and Si, Al, Mn, Fe, Mg, and Ca Is also within the general range. Therefore, comparative examples exceeding the upper and lower limits and the upper and lower limits are not provided.
Tables 5 to 21 are for flux-cored wires. For example, Table 5 is the first embodiment, Table 6 is the second embodiment, Table 7 is the third embodiment, and Table 8 is the fourth embodiment. Corresponding. And for example, No. of Tables 5-8. 1-1 to 1-26 are Nos. 1 and 2 in Tables 1 and 2. No. 1 titanium oxide raw material is used (details will be described later).

  First, the manufacturing method of the titanium oxide raw material which is a test material is demonstrated. As described above, there are mainly two methods for producing a titanium oxide raw material: a firing method and a melting method. When the firing method is used, the amount of Fe is high, and when the melting method is used, the amount of Fe is low. By using different manufacturing methods and titanium raw materials, the raw materials for fillet welding (higher Fe content is preferred) and vertical welding (lower Fe content is preferred) were used.

  First, the firing method will be described. The raw materials used were natural rutile, lucoxin and illuminite as Ti sources. These were properly used according to the physical properties of the target titanium oxide raw material, and mixed and used. In application, raw materials with less impurities were used, so specific gravity, magnetic force, and flotation were conducted for the purpose of concentrating titanium oxide raw materials and reducing impurities. As the Si, Al, Fe, Mn, Mg, and Ca sources, oxides (including complex oxides) and carbonates of Si, Al, Fe, Mn, Mg, and Ca were used (added).

  As a firing method, a rotary kiln was used as a firing furnace. The firing atmosphere was a CO atmosphere. In addition, C source was added to the firing raw material.

  Next, the melting method will be described. The raw material used was low-cost natural illuminite as a Ti source. In application, raw materials with less impurities were used, so specific gravity, magnetic force, and flotation were conducted for the purpose of concentrating titanium oxide raw materials and reducing impurities. As the Si, Al, Fe, Mn, Mg, and Ca sources, oxides (including complex oxides) and carbonates of Si, Al, Fe, Mn, Mg, and Ca were used (added).

  As a melting method, illuminite, other raw materials (oxide, carbonate) and deoxidizer (C source) are mixed and heated to 1800 to 2000 ° C. in an arc furnace to return Fe oxide in the illuminite. To a molten state. Since Fe has a low melting point, it gathered at the bottom of the furnace, and oxides composed of Ti, Si, Al, Mn, Fe, Mg, Ca and other impurities were generated at the top of the furnace.

The oxide thus obtained was subjected to coarse pulverization → pulverization → particle size adjustment to obtain a solvent raw material.
Further, in order to remove impurities such as C and S in the deoxidizer, pickling and baking were performed as post-processing.

And after manufacturing a titanium oxide raw material, in order to adjust trace elements, such as the amount of Fe, Mn, Al, Si, Mg, Ca which exist on the surface, the oxide of Fe, Mn, Al, Si, Mg, Ca and Carbonate or the like was added, and firing (sintering) was performed to such an extent that the surface of the titanium oxide raw material slightly melted. The firing temperature was about 800 to 1300 ° C., and the material was sintered together with the additive raw material in a rotary kiln.
Table 1 shows the bulk composition of titanium oxide raw materials Nos. 1 to 16.

  Next, a method for analyzing the atomic percentage on the particle surface of the titanium oxide raw material will be described. The analyzer is as follows.

(1) First analyzer Device: WD / ED combine manufactured by JEOL Ltd. Using electronic probe microanalyzer (EPMA) JXA-8200 Analysis conditions: acceleration voltage 15 kv, irradiation current 5 × 10 ⁻¹⁰ A

(2) Second analyzer Device: Scanning electron microscope with EDS manufactured by Hitachi High-Tech Fielding Co., Ltd. S-3700N Use EDS: GENESIS 400 series manufactured by EDAX Japan Co., Ltd. Analysis conditions: acceleration voltage 15 kv, irradiation current 5 × 10 ^{− 12} A
In addition, although it analyzed by the 1st and 2nd EDX apparatus, the analysis result was equivalent in both.

(3) Quantitative analysis method Quantitative analysis was performed by standardless analysis. The relative intensity ratio between the spectrum of the standard sample stored in the computer database and the measured spectrum was calculated, and the correction was calculated so that the total was 100%.

  The analysis method is as follows. In EDX, C tape (Nisshin EM Co., Ltd., SEM conductive tape, carbon double-sided tape) was applied to an aluminum base, and the raw material (about 100 mg) was placed on it. The raw material was well adhered onto the C tape. In order to ensure electrical conductivity, 5 particles having a range (10 μm × 10 μm rectangular region) in which Os vapor deposition is performed and the surface of the raw material at a high magnification (about 2000 times) is relatively flat and no foreign matter is present or adhered thereto. A random selection was made and the atomic percentage (atomic%) of one field per particle was measured.

Analysis conditions: Energy full scale: 20 KeV (10 eV / ch, 2 Kch)
Effective time: 60 seconds Acceleration voltage: 15.0 KV
Probe current: 5.0 × 10 ⁻¹⁰ A

  The calculation method of x, y, z of the numerical formulas 1-3 demonstrated by the surface analysis of the said titanium oxide raw material is as follows. From the measurement results of the above-mentioned five points (points of five particles), the values of Equations 1 to 3 shown below are obtained, and the average values of x, y, and z at the five points are calculated.

  In the calculation methods of Equations 2 and 3, the denominator and the numerator are each independently subjected to an arithmetic average of 5 points, and division is performed by the obtained average value. When the average value of the denominator is zero (all five points are zero), the values of Equations 2 and 3 are infinite.

  Table 2 shows the analysis results of the atomic percentages on the particle surface of the titanium oxide raw material (that is, the EDX analysis results).

  And the evaluation result of the welding test using each titanium oxide raw material in a flux cored wire is shown in Table 3. In addition, although the flux cored wire used in the welding test using a titanium oxide raw material was produced using the titanium oxide raw material shown in Tables 1-3, the compounding amount of components other than the titanium oxide raw material is shown in Table 4 below. The welding conditions are as follows. Moreover, the manufacturing method of a flux cored wire is the same as the method of postscript. Moreover, the standard of evaluation of familiarity and bead shape is shown in FIG.

(Welding conditions)
○ Flaked wire welding current: about 220A
Welding voltage: about 26V
Welding power supply, polarity: 350A thyristor power supply, DCEP
Welding posture: Standing upward shield gas Type: 100 vol% CO ₂
Shield flow rate: 25L / min

  The overall evaluation is “◎” when both the familiarity and the bead shape are “◎”, “◎” when one is “、”, and “◯” when the other is “◯”. In addition, when both the familiarity and the bead shape are “Δ”, the overall evaluation is “Δ”, and when either is “×”, it is “X”.

Next, the manufacturing method of the flux cored wire (the thing of Tables 5-21) used by the present Example is demonstrated (Tables 5-21).
(Wire production method)
While feeding the steel strip in the longitudinal direction, it was formed into an open tube by a forming roll. Next, required amounts of titanium oxide raw material and metal or alloy, Fe powder, and the like were added to the flux so that the chemical compositions shown in Tables 5 to 21 were obtained. Next, a flux-cored wire was produced by processing the cross section into a circle. Then, the wire diameter was 1.0-1.6 mm by cold drawing. Annealing is performed for the purpose of softening the work-hardened wire during the cold working.

  Tables 5 to 21 show component compositions of the flux-cored wire. In the table, those not satisfying the scope of the present invention are indicated by underlining the numerical values. Further, “Met.Si”, “Met.Al”, and “Met.Ti” are metal Si, metal Al, and metal Ti, respectively, and “Total Si” is the Si equivalent of metal Si and Si oxide. It is the sum with Si conversion amount. In addition, metal Si, metal Al, and metal Ti are Si conversion amount, Al conversion amount, and Ti conversion amount, respectively. Further, “Si oxide” is the amount of Si in the Si oxide. The same applies to Table 4.

Here, Tables 5 to 8 show the sample numbers of Tables 1 to 3. No. 1 titanium oxide raw material is used. This sample No. 1 is a range where “Si + Al” is more preferable, and “Ti / Fe + Mn” and “O / (Fe + Mn)” are preferable ranges.
Tables 9 to 12 show the sample numbers of Tables 1 to 3. No. 7 titanium oxide raw material is used. This sample No. In No. 7, “Si + Al” is outside the more preferable range.

Tables 13 to 16 show the sample numbers of Tables 1 to 3. No. 9 titanium oxide raw material is used. This sample No. 9, “Si + Al” is a more preferable range, but “O / (Fe + Mn)” is out of the preferable range.
Tables 17 to 20 show the sample numbers of Tables 1 to 3. 10 titanium oxide raw materials are used. This sample No. In No. 10, “Si + Al” is out of the more preferable range, “O / (Fe + Mn)” is out of the preferable range, and the content of TiO ₂ is low.
Table 21 shows the sample numbers of Tables 1-3. 14 titanium oxide raw materials are used. This sample No. In “14”, “Si + Al” is out of the range, and “Ti / Fe + Mn” and “O / (Fe + Mn)” are out of the preferable ranges.

  Tables 5 to 21 show the first embodiment (related to mild steel FCW), the second embodiment (related to low temperature toughness), the third embodiment (related to cryogenic toughness), and the fourth embodiment (related to HT), respectively. Compatible with flux-cored wire.

  The following tests were performed on the flux-cored wire thus manufactured. In each test, to correspond to the first embodiment (related to mild steel FCW), the second embodiment (related to low temperature toughness), the third embodiment (related to cryogenic toughness), and the fourth embodiment (related to HT). , Changed the conditions.

<Welding workability>
Here, the bead shape was also included in the welding workability and evaluated.
(Test base material for welding workability confirmation)
[Corresponding to the first to third embodiments]
A test plate having a thickness of 12 mm and a length of 400 mm made of a welded structural steel plate (SM490A) defined in JIS G G3106 was used as a test base material for confirming welding workability.
[Corresponding to the fourth embodiment]
A test plate having a plate thickness of 12 mm and a length of 400 mm made of a high yield point steel material for welded structure (SHY685) defined in JIS G3218 was used as a test base material for confirming welding workability.

(Welding conditions)
Welding current: 240A
Welding voltage: 26V
Welding power supply, polarity: 350A thyristor power supply, DCEP
Welding posture: Standing upward shield gas Type: 100 vol% CO ₂
Shield flow rate: 25L / min

<Bead shape>
[Corresponding to the first to fourth embodiments]
At 240A, the welded portion where the fillet welding progressed was observed, and the bead shape was visually evaluated. A smooth and good bead shape was indicated by “◯”, and a bead shape convex was indicated by “X”. Furthermore, “◎” was given to those having a smooth bead shape and particularly excellent including bead appearance and bead familiarity.

<Sensory evaluation excluding bead shape>
[Corresponding to the first to fourth embodiments]
The evaluation criteria were “◯” when the arc stability was good, and when the fume generation amount and the spatter generation amount were excellent, and “X” when they were inferior.

<Cold cracking>
[Corresponding to the fourth embodiment]
About what respond | corresponds to 4th Embodiment, the presence or absence of the generation | occurrence | production of the low temperature crack after welding metal preparation was evaluated. The evaluation criteria were “◯” when no cold cracking occurred after welding and “X” when it occurred.

<Mechanical properties>
(Test base material for mechanical property confirmation)
All weld metals according to JIS Z3313 were prepared and the mechanical properties were investigated.
[Corresponding to the first to third embodiments]
A test plate having a thickness of 20 mm and a length of 300 mm made of a welded steel rolled steel material (SM490A) defined in JIS G3106 was used as a test base material for confirming mechanical properties.
[Corresponding to the fourth embodiment]
A test plate having a thickness of 20 mm and a length of 300 mm made of a high yield point steel for welded structure (SHY685) as defined in JIS G3218 was used as a test base material for confirming mechanical properties.

(Welding conditions)
Welding current: 280A
Welding voltage: 30V
Welding power supply, polarity: 350A thyristor power supply, DCEP
Welding posture: Downward welding Shield gas type: 100% by volume CO ₂
Shield flow rate: 25L / min
Interpass temperature: 135-165 ° C
Heat input: about 1.8kJ / mm
Wire diameter: 1.2mm
Wire protrusion length: 25mm

<Tensile strength, impact performance (impact value)>
[Corresponding to the first embodiment]
According to JIS Z3313, tensile strength and -20 ° C absorbed energy (toughness) were evaluated.
Evaluation criteria for tensile strength were “「 ”for 570 MPa or more,“ ◯ ”for 490-569 MPa, and“ x ”for 489 MPa or less.
The evaluation criteria for impact performance were 120J or more as “◎”, 47J to 119J as “◯”, and 46J or less as “x”.

[Corresponding to the second embodiment]
According to JIS Z3313, tensile strength and -40 ° C absorbed energy (toughness) were evaluated.
Evaluation criteria for tensile strength were “「 ”for 570 MPa or more,“ ◯ ”for 490-569 MPa, and“ x ”for 489 MPa or less.
The evaluation criteria regarding impact performance were 80J or more as “◎”, 47 to 79J as “◯”, and 46J or less as “X”.

[Corresponding to the third embodiment]
According to JIS Z3313, tensile strength and -60 ° C absorbed energy (toughness) were evaluated.
Evaluation criteria for tensile strength were “「 ”for 540 MPa or more,“ ◯ ”for 490-539 MPa, and“ x ”for 489 MPa or less.
The evaluation criteria regarding impact performance were 80J or more as “◎”, 47 to 79J as “◯”, and 46J or less as “X”.

[Corresponding to the fourth embodiment]
According to JIS Z3313, tensile strength and -40 ° C absorbed energy (toughness) were evaluated.
The evaluation criteria regarding the tensile strength were “◎” for 800 MPa or more, “◯” for 780 to 799 MPa, and “x” for 779 MPa or less.
The evaluation criteria regarding impact performance were 80J or more as “◎”, 47 to 79J as “◯”, and 46J or less as “X”.

In the evaluation corresponding to these first to fourth embodiments, as mechanical property evaluation, in the case of tensile strength “◎”, impact performance “◎”, “◎”, tensile strength “◯”, impact performance “◎”, Or, if the tensile strength is “◎” and the impact performance is “○”, “○ to ◎”, if the tensile strength is “○”, if the impact performance is “○”, “○”, and either the tensile strength or impact performance is In the case of “x”, “x” was used.
These results are shown in Tables 22-38.

  As shown in Tables 22-38, no. 1-1 to 1-4, No, 1-9 to 1-11, No. 1-15 to 1-17, No.1. 1-21 to 1-23, no. 7-1 to 7-4, No.7. 7-9 to 7-11, no. 7-15 to 7-17, no. 7-21 to 7-23, no. 9-1 to 9-4, no. 9-9 to 9-11, no. 9-15 to 9-17, no. 9-21 to 9-23, no. 10-1 to 10-4, no. 10-9 to 10-11, no. 10-15 to 10-17, no. Since 10-21 to 10-23 satisfy | filled the range of this invention, the favorable result was obtained in each evaluation.

  No. In 1-5, since the titanium oxide raw material was insufficient, the beat shape was deteriorated. No. In 1-6, since there were many titanium oxide raw materials, the scale bead generate | occur | produced and the bead shape deteriorated. Moreover, since there was much Mn amount, intensity | strength increased and toughness fell. No. In 1-7, since the amount of C was large, the arc force became strong and the bead shape deteriorated. In addition, the amount of spatter increased due to the large amount of “Met.Al + Mg”. No. In 1-8, the bead shape deteriorated because the amount of Met.Si was small. Further, since the amount of F was large, the amount of fume was increased, and the amount of “Na + K” was large, so that the moisture absorption resistance was inferior. No. In 1-12, since the amount of B was large and remarkable, the strength increased and the toughness decreased. No. For 1-13, since the amount of B and Ni was small, the effect could not be confirmed, and the toughness decreased. No. Since 1-14 had a large amount of Nb, toughness was lowered.

  No. Since 1-18 had a large amount of Ti, the strength was remarkably increased and the toughness was lowered. No. Since 1-19 had a small amount of Ni, its effect could not be confirmed, and toughness decreased. No. Since 1-20 had a large amount of Nb, toughness was lowered. No. Since 1-24 had a large amount of Mo, the strength was remarkably increased and the toughness was lowered. Furthermore, cold cracking occurred. No. For 1-25, since the amount of Ni was small, the effect could not be confirmed, and the toughness decreased. No. Since 1-26 has much Nb amount, toughness fell.

  No. In 7-5, since the titanium oxide raw material was insufficient, the beat shape was deteriorated. Further, since the amount of “Met.Al + Mg” is small, the toughness is lowered. No. In 7-6, since there were many titanium oxide raw materials, the scale bead generate | occur | produced and the bead shape deteriorated. Moreover, since the amount of Mn was small, the strength decreased. No. In 7-7, since the amount of C was large, the arc force became strong and the bead shape deteriorated. In addition, the amount of spatter increased due to the large amount of “Met.Al + Mg”. No. Since 7-8 had a small amount of C, the strength decreased. In addition, the bead shape deteriorated because the total Si amount and Met.Si amount were insufficient. Moreover, since the amount of Na + K was small, the amount of sputtering increased. No. Since 7-12 had a large amount of Ni, the strength increased remarkably and the toughness decreased. No. Since 7-13 had a large amount of Cr, the strength increased remarkably and the toughness decreased. No. Since 7-14 had much V amount, toughness fell.

  No. For 7-18, the amount of B was small, so the effect could not be confirmed, and the toughness decreased. No. Since 7-19 had a small amount of Ni, its effect could not be confirmed, and toughness decreased. No. Since 7-20 has a large amount of Cr, the strength increased remarkably and the toughness decreased. No. Since 7-24 had much V amount, toughness fell. No. Since 7-25 had a large amount of Ni, the strength increased remarkably and the toughness decreased. No. Since 7-26 had a large amount of Mo, the strength increased remarkably and the toughness decreased. Furthermore, cold cracking occurred.

  No. In 9-5, since the titanium oxide raw material was insufficient, the bead shape deteriorated. Moreover, since the flux rate was less than 10% by mass, the stability of the arc deteriorated and the amount of spatter increased. No. In 9-6, since there were many titanium oxide raw materials, the scale bead generate | occur | produced and the bead shape deteriorated. No. In 9-7, since the amount of C was large, the bead shape deteriorated. Further, since the amount of F was large, the amount of fume was increased, and the amount of “Na + K” was large, so that the moisture absorption resistance was inferior. No. In 9-8, since the amount of Total.Si was insufficient, the viscosity decreased and the beat shape deteriorated. In addition, the amount of spatter increased due to the large amount of “Met.Al + Mg”. No. Since 9-12 had a large amount of Ni, the strength increased remarkably and the toughness decreased. No. Since 9-13 had a large amount of B and Cr, the strength increased remarkably and the toughness decreased. No. Since 9-14 has much V amount, toughness fell.

  No. For 9-18, the amount of Ti was small, so the effect could not be confirmed, and the toughness decreased. No. Since 9-19 had a large amount of B, the strength increased remarkably and the toughness decreased. No. Since 9-20 had a large amount of Ni, the strength increased remarkably and the toughness decreased. No. Since 9-24 had a large amount of Ni, the strength increased remarkably and the toughness decreased. Furthermore, cold cracking occurred. No. For 9-25, since the amount of Mo was small, the effect could not be confirmed, and the strength decreased. No. Since 9-26 had a small amount of Ni, its effect could not be confirmed and the toughness was lowered.

  No. In 10-5, since the titanium oxide raw material was insufficient, the beat shape was deteriorated. No. In 10-6, the toughness deteriorated because the total Si amount was large. Furthermore, hot cracking occurred. No. In 10-7, since the amount of C was large, the beat shape deteriorated. In addition, the amount of spatter increased due to the large amount of “Met.Al + Mg”. No. In 10-8, since the amount of Met.Si was insufficient, the beat shape was deteriorated. Further, since the amount of F was large, the amount of fume was increased, and the amount of “Na + K” was large, so that the moisture absorption resistance was inferior. No. For 10-12, since the amount of B and Ni was small, the effect could not be confirmed, and the toughness decreased. No. Since 10-13 had a large amount of Ni, the strength increased remarkably and the toughness decreased. No. Since 10-14 had a large amount of Nb, the toughness decreased.

  No. Since 10-18 had a large amount of B, the strength was remarkably increased and the toughness was lowered. No. Since 10-19 had a large amount of Ti, the strength was remarkably increased and the toughness was lowered. No. Since 10-20 had a large amount of V, toughness decreased. No. For 10-24, since the amount of Mo was small, the effect could not be confirmed, and the strength decreased. No. Since 10-25 had a large amount of Mo, the strength was remarkably increased and the toughness was lowered. Furthermore, cold cracking occurred. No. Since 10-26 had a large amount of V, toughness decreased. No. In 14-1, since the value of “Si + Al” on the particle surface of the titanium oxide raw material exceeded the upper limit value, the beat shape deteriorated.

  The present invention has been described in detail with reference to the embodiments and examples. However, the gist of the present invention is not limited to the above-described contents, and the scope of right is widely interpreted based on the description of the claims. Must. Needless to say, the contents of the present invention can be widely modified and changed based on the above description.

Claims (4)

A flux-cored wire for gas shielded arc welding,
Per total wire mass,
Titanium oxide raw material in the form of particles: 5.0 to 9.0% by mass,
C: 0.02-0.11 mass%,
Sum of Si equivalent amount of metal Si and Si equivalent amount of Si oxide: 0.3 to 1.2% by mass,
Si equivalent amount of metal Si: 0.2 mass% or more,
Mn: 1.0 to 3.0% by mass,
Total of Al in terms of metal Al and Mg: 0.1 to 1.0% by mass,
Total of Na equivalent amount in Na compound and K equivalent amount in K compound: 0.05 to 1.50 mass%,
F conversion amount in the F compound: 0.02 to 0.85% by mass, the balance being Fe and inevitable impurities,
The flux filling rate per total mass of the wire is 10 to 25% by mass,
The titanium oxide raw material is based on the total mass of the titanium oxide raw material,
TiO ₂ : 58.0 to 99.0% by mass,
Si: 2.5% by mass or less,
Al: 3.0% by mass or less,
Mn: 5.0% by mass or less,
Fe: 35.0 mass% or less,
Mg: 5.0% by mass or less,
Ca: a composition having a composition of 2.0% by mass or less, and an oxide composed of at least one of Ti, Fe, Mn, Al, and Si is present on the particle surface of the titanium oxide raw material; and This oxide has a flux-cored wire for gas shielded arc welding, wherein the atomic percentage of Al and Si satisfies 1 ≦ Al + Si ≦ 10.
(However, wire components other than the titanium oxide raw material exclude components contained in the titanium oxide raw material.) Furthermore, per total wire mass,
B: 0.0003 to 0.0130 mass%,
Ni: 0.1 to 1.0% by mass,
Cr: 0.20 mass% or less,
Nb: 0.05% by mass or less,
V: The flux-cored wire for gas shielded arc welding according to claim 1, wherein the wire is suppressed to 0.05% by mass or less. Furthermore, per total wire mass,
Ti conversion amount of metal Ti: 0.05-0.40 mass%,
B: 0.0003-0.0150 mass%,
Ni: 0.3 to 3.0% by mass,
Cr: 0.20 mass% or less,
Nb: 0.05% by mass or less,
V: The flux-cored wire for gas shielded arc welding according to claim 1, wherein the wire is suppressed to 0.05% by mass or less. Furthermore, per total wire mass,
Ni: 0.3 to 3.0% by mass,
Mo: contains 0.01 to 0.50 mass%,
Nb: 0.05% by mass or less,
V: The flux-cored wire for gas shielded arc welding according to claim 1, wherein the wire is suppressed to 0.05% by mass or less.