KR20210042023A - Welding material, welded metal and electroslag welding method - Google Patents

Abstract

Provided is a welding material which can acquire weld metal with excellent low temperature toughness. To this end, an electroslag welding wire, based on the entire mass of the wire, comprises 94 mass% or more of Fe, each of C, Si, Mn and Mo within a predetermined range, and 0.01 mass% or more and less than 0.08 mass% of Ti, wherein it is regulated that Al is at less than 0.06 mass% (including 0 mass%), B is at less than 0.0070 mass% (including 0 mass%), and Cu is at less than 1.5 mass% (including 0 mass%). A molten flux, based on the entire mass of the flux, comprises 10 mass% or more and 45 mass% or less of Ca equivalence of Ca compound, 0 mass% or more and 25 mass% or less of F equivalence of F compound, and 10 mass% or more and 50 mass% or less of Al_2O_3, wherein it is regulated that SiO_2 is at 35 mass% or less (including 0 mass%), and B_2O_3 is at 1.0 mass% or less (including 0 mass%). The electroslag welding wire and the molten flux are combined for use.

Description

Welding material, welding metal and electroslag welding method {WELDING MATERIAL, WELDED METAL AND ELECTROSLAG WELDING METHOD}

The present invention relates to a welding material, a weld metal, and an electroslag welding method.

In general, in fields such as buildings and shipbuilding, there is a tendency for the plate thickness to increase as the structure increases in size. For these structures, conventionally, upright welding by high-efficiency electrogas arc welding is used, but electrogas arc welding has problems in the working environment due to arc radiation heat, generation of fumes and spatters for welding workers. In addition, there is also a problem that the shield deteriorates with an increase in the plate thickness.

In contrast, electroslag welding using Joule heat of molten slag as a heat source is not an exposed arc, but because heat is generated in the molten slag to melt the wire and the base material, arc radiant heat is not generated, and fume and spatter are not generated. It is a welding method in which there is little generation of dust and a good working environment is obtained. In addition, since electroslag welding shields the weld metal from the atmosphere with molten slag, shielding gas is not necessary, and the shielding effect does not deteriorate even if the plate thickness increases. Intrusion into molten metal such as the like can be effectively prevented.

In recent years, there is a demand for improvement in toughness of building members and welds (welded metals) of large buildings, and many proposals have been made regarding electroslag welding used for steel frames for buildings and the like. For example, in Patent Document 1, as a weld joint obtained by welding a high tensile strength steel sheet of 490 to 740 MPa class having a plate thickness of 40 mm or more, in high heat input electroslag welding with a welding heat input of 400 kJ/cm or more and 1000 kJ/cm or less, the welding line A weld joint in which good toughness is obtained in the direction is disclosed.

Japanese Patent Laid-Open No. 2011-224612

However, the electroslag welded joint described in Patent Document 1 is intended for the field of steel frames for buildings, and sufficient toughness is obtained at room temperature, but use in fields such as shipbuilding is not expected, for example -20 In an environment at a low temperature of C or lower, further improvement of the toughness of the weld metal is required.

The present invention has been made in view of these problems, and an object of the present invention is to provide a welding material capable of obtaining a welding metal having excellent low-temperature toughness, a welding metal obtained by welding using the welding material, and an electroslag welding method.

The welding material of the present invention is a welding material used for electroslag welding,

Electroslag welding wire,

Per total mass of wire,

Fe: 94% by mass or more,

C: 0.01% by mass or more and 0.05% by mass or less,

Si: 0.05% by mass or more and 0.40% by mass or less,

Mn: 1.0% by mass or more and 1.8% by mass or less,

Mo: 0.1% by mass or more and 0.8% by mass or less,

Ti: 0.01% by mass or more and less than 0.08% by mass,

Al: less than 0.06 mass% (including 0 mass%),

B: less than 0.0070 mass% (including 0 mass%),

Cu: It is regulated to be less than 1.5% by mass (including 0% by mass),

Melt flux,

Per total mass of flux,

Ca compound value in terms of Ca: 10% by mass or more and 45% by mass or less,

F conversion value of the compound F: 0% by mass or more and 25% by mass or less,

Al ₂ O ₃ : contains 10% by mass or more and 50% by mass or less,

SiO ₂ : 35 mass% or less (including 0 mass%),

B ₂ O ₃ : It is regulated to 1.0% by mass or less (including 0% by mass),

It is characterized in that the electroslag welding wire and the melting flux are used in combination.

It is preferable that the melting flux in the welding material is regulated to less than 10% by mass (including 0% by mass) of MnO per total mass of the flux.

In addition, the weld metal of the present invention is a weld metal obtained by electroslag welding using the welding material described above,

Per total mass of weld metal,

C: 0.03 mass% or more and 0.08 mass% or less,

Si: 0.10 mass% or more and 0.40 mass% or less,

Mn: 1.0% by mass or more and 1.7% by mass or less,

Mo: 0.1% by mass or more and 0.8% by mass or less,

Ti: 0.001% by mass or more and less than 0.040% by mass,

Al: less than 0.019% by mass (not including 0% by mass),

B: less than 0.0045% by mass (not including 0% by mass),

O: less than 0.0300 mass% (including 0 mass%),

Cu: While being regulated to be less than 1.45% by mass (including 0% by mass),

It is characterized in that the balance is Fe and unavoidable impurities.

In addition, the electroslag welding method of the present invention is characterized in that welding is performed using the above welding material.

According to the present invention, for example, a welding material suitable for the field of shipbuilding and the like and capable of obtaining a weld metal having excellent low-temperature toughness, a weld metal obtained by welding using the welding material, and an electroslag welding method are provided. can do.

1 is a diagram showing a joint shape in a welding test.

Hereinafter, an embodiment for carrying out the present invention will be described in detail. On the other hand, the present invention is not limited to the embodiments described below, and can be carried out with arbitrary changes within the scope not departing from the gist of the present invention.

As a result of intensive research in order to solve the above problems, the present inventors have found that by reducing the amount of oxygen in the weld metal and optimizing the type and content of inclusions in the weld metal, it is possible to obtain a weld metal excellent in low-temperature toughness.

Specifically, the content of each element such as Al, Ti, and B in the wire is controlled so that the amount of oxygen in the weld metal is reduced as much as possible by controlling the melt flux component, and the content is optimal for the amount of oxygen in the weld metal. Thereby, it is possible to obtain a weld metal excellent in low-temperature toughness that can be used even in a low-temperature environment of -20°C or lower. That is, it is possible to obtain a weld metal excellent in low-temperature toughness by using a welding material obtained by combining a melting flux with a component controlled in a predetermined range and an electroslag welding wire for electroslag welding.

Hereinafter, with respect to each component in the electroslag welding wire and the melting flux contained in the welding material according to the present embodiment, the reason for the addition of the component and the reason for limiting the content will be described in detail. As described above, the welding material of the present embodiment can obtain a weld metal having excellent low-temperature toughness by appropriately controlling both the wire component and the melt flux component.

[One. Electroslag welding wire]

First, a wire for electroslag welding according to the present embodiment will be described. This wire for electroslag welding is a solid wire or a flux cored wire. In this embodiment, it is preferable to use a flux-cored wire. In addition, the wire according to the present embodiment is a metal flux-cored wire.

Electroslag welding wire according to this embodiment,

Per total mass of wire,

Fe: 94% by mass or more,

C: 0.01% by mass or more and 0.05% by mass or less,

Si: 0.05% by mass or more and 0.40% by mass or less,

Mn: 1.0% by mass or more and 1.8% by mass or less,

Mo: 0.1% by mass or more and 0.8% by mass or less,

Ti: 0.01% by mass or more and less than 0.08% by mass,

Al: less than 0.06 mass% (including 0 mass%),

B: less than 0.0070 mass% (including 0 mass%),

Cu: It is regulated to be less than 1.5% by mass (including 0% by mass).

<C: 0.01% by mass or more and 0.05% by mass or less>

C is an element that contributes to securing the strength of the weld metal by forming a solid solution or compound together with Fe.

If the C content in the wire is less than 0.01% by mass, the above action cannot be effectively exhibited, so the C content per total mass of the wire is made 0.01% by mass or more, preferably 0.02% by mass or more.

On the other hand, if the C content in the wire exceeds 0.05% by mass, it causes an increase in the number of compound particles, and since the Fe and C compound particles act as a starting point for void formation during the Charpy test, the low-temperature toughness of the weld metal is lowered. Therefore, the C content per total mass of the wire is 0.05% by mass or less, and preferably 0.045% by mass or less.

<Si: 0.05% by mass or more and 0.40% by mass or less>

Since Si is a deoxidation element, it is an element that reduces the oxygen concentration in the weld metal by adding Si to the weld metal from the wire and improves the low-temperature toughness.

If the Si content in the wire is less than 0.05% by mass, the above action cannot be effectively exhibited, so the Si content per total mass of the wire is set at 0.05% by mass or more, preferably 0.10% by mass or more.

On the other hand, if the Si content in the wire exceeds 0.40% by mass, the strength of the weld metal becomes excessive and the low-temperature toughness decreases, so the Si content per total mass of the wire is made 0.40% by mass or less, preferably 0.30% by mass or less. do.

<Mn: 1.0% by mass or more and 1.8% by mass or less>

Mn is an element that contributes to securing the strength of the weld metal by solid solution strengthening with Fe.

When the Mn content in the wire is less than 1.0% by mass, the above effect cannot be exhibited effectively, and therefore the Mn content per total mass of the wire is set at 1.0% by mass or more, preferably at least 1.1% by mass.

On the other hand, if the Mn content in the wire exceeds 1.8% by mass, the strength of the weld metal becomes excessive and the low-temperature toughness decreases, so the Mn content per total mass of the wire is 1.8% by mass or less, preferably 1.7% by mass or less. do.

<Mo: 0.1% by mass or more and 0.8% by mass or less>

Mo is an element that contributes to securing the strength of the weld metal by solid solution strengthening with Fe.

If the Mo content in the wire is less than 0.1% by mass, the above action cannot be effectively exhibited, so the Mn content per total mass of the wire is 0.1% by mass or more, preferably 0.2% by mass or more.

On the other hand, when the Mo content in the wire exceeds 0.8% by mass, the strength of the weld metal becomes excessive and the low-temperature toughness decreases, so the Mo content per total mass of the wire is 0.8% by mass or less, preferably 0.7% by mass or less. do.

<Ti: 0.01% by mass or more and less than 0.08% by mass>

Ti is an element necessary for preventing formation of coarse grain boundary ferrite in the weld metal as a Ti oxide, which serves as a nucleus that generates acyclic ferrite.

If the Ti content in the wire is less than 0.01% by mass, the formation of Ti oxide is insufficient, and the effect of improving the toughness of the weld metal cannot be obtained. Therefore, the Ti content per total mass of the wire is made 0.01% by mass or more, preferably It is set as 0.015 mass% or more, More preferably, it is set as 0.020 mass% or more.

On the other hand, if the Ti content in the wire is 0.08 mass% or more, the Ti precipitates in the weld metal are excessively large, and the toughness of the weld metal is rather reduced, so the Ti content per total mass of the wire is set to be less than 0.08 mass%, preferably 0.075. It is set as less than mass%, more preferably, it is set as less than 0.070 mass%.

<Al: less than 0.06% by mass (including 0% by mass)>

Since Al is a deoxidation element, by containing Al in the weld metal, it is an element that lowers the oxygen concentration in the weld metal and improves the low-temperature toughness of the weld metal. In addition, Al is an optional component in the wire according to the present embodiment.

However, as described above, for the purpose of further reducing the amount of oxygen in the weld metal, when Al in the wire, which is a deoxidation element, is added excessively, coarse inclusions are formed in the metal structure of the weld metal, rather than the weld metal. Since the toughness of is lowered, in the case of containing Al in the wire as an optional component, the Al content per total mass of the wire is less than 0.06 mass%, preferably less than 0.055 mass%, more preferably less than 0.050 mass%. It is done.

<B: less than 0.0070% by mass (including 0% by mass)>

B is an element that improves the hardenability of the weld metal, and is an element that improves toughness by suppressing the growth of saltpeter ferrite. Particularly, when the O content in the weld metal is about 0.0350% by mass, the effect is remarkable. However, when the O content in the weld metal is 0.0300% by mass or less and the metal structure is sufficiently refined, the influence of the B content on toughness is small. Therefore, B is an optional component in the wire according to the present embodiment.

However, in the case where B in the wire is excessively added for the purpose of improving the toughness of the weld metal, the hardenability of the weld metal becomes excessive, so the toughness of the weld metal is rather due to the formation of island martensite. Because of deterioration, when B is contained in the wire as an optional component, the B content per total mass of the wire is less than 0.0070 mass%, preferably less than 0.0065 mass%, and more preferably less than 0.0060 mass%.

<Cu: less than 1.5% by mass (including 0% by mass)>

Cu is an element used for strength adjustment.

However, if the Cu content in the wire is 1.5% by mass or more, it may deteriorate in terms of strength, so the Cu content per total mass of the wire is less than 1.5% by mass, preferably less than 1.0% by mass, more preferably It should be less than 0.5% by mass.

<Fe: 94% by mass or more>

Fe is a main component of the electroslag welding wire according to the present embodiment. The Fe content per total mass of the wire is 94% by mass or more, preferably 95% by mass or more, and more preferably 97% by mass or more from the relationship between the amount of welding and the composition of other components. It is practical that Fe is 99% by mass or less.

Here, the wire for electroslag welding according to the present embodiment contains 96 mass% or more in total of the aforementioned C, Si, Mn, Mo, Ti, Al, B, Cu, and Fe. It is preferable that this total is 98 mass% or more.

<balance>

The remainder of the wire for electroslag welding according to the present embodiment may contain 4% by mass or less of other components within a range not departing from the effect of the present embodiment. In addition, inevitable impurities are included as the balance. Examples of inevitable impurities include P, S, Ni, Cr, V, Nb, Sn, Zr, O and N. For example, P and S may contain 0.05 mass% or less, V and Nb 0.10 mass% or less, Sn and Zr 0.010 mass% or less, and N may contain 0.010 mass% or less. In addition, Cr and Ni are elements for adjusting the strength, and may be contained in an amount of, for example, 1.5% by mass or less.

<Method of manufacturing wire>

On the other hand, the wire according to the present embodiment described above is not particularly limited with respect to the manufacturing method or the like as long as the content of the component contained within the above range, and can be manufactured by a known method.

[2. Melt flux]

Next, the melt flux according to the present embodiment will be described. In electroslag welding, since the welding uses molten slag as a heat source, a molten flux is used.

The melt flux according to this embodiment,

Per total mass of flux,

Ca compound value in terms of Ca: 10% by mass or more and 45% by mass or less,

F conversion value of the compound F: 0% by mass or more and 25% by mass or less,

Al ₂ O ₃ : contains 10% by mass or more and 50% by mass or less,

SiO ₂ : 35 mass% or less (including 0 mass%),

B ₂ O ₃ : It is regulated to 1.0% by mass or less (including 0% by mass).

<Ca compound value in terms of Ca: 10% by mass or more and 45% by mass or less>

Ca contained in the melting flux is a basic component, and is an effective component for controlling the viscosity and melting point of the molten slag. In addition, Ca is also a component having a high effect of reducing the amount of oxygen in the weld metal. Since Ca in the melt flux _{is added as a Ca compound such as CaF 2} and CaO, in the present embodiment, the Ca compound in the melt flux is defined as a value converted to Ca.

If the Ca compound in the melt flux in terms of Ca is less than 10% by mass, the above action cannot be effectively exhibited. Therefore, the Ca compound value in terms of Ca per the total mass of the melting flux is 10% by mass or more, preferably 12% by mass. It is set as above, and more preferably, it is set as 15 mass% or more.

On the other hand, if the Ca compound in the melt flux in terms of Ca exceeds 45% by mass, undercut and slag winding occur, the Ca compound value in terms of Ca per the total mass of the melting flux is 45% by mass or less, preferably 43% by mass. % Or less, more preferably 40 mass% or less.

<F conversion value of the compound F: 0% by mass or more and 25% by mass or less>

F contained in the melting flux is also a basic component like Ca, and is an effective component for controlling the viscosity and melting point of the molten slag. Further, F is also a component having a high effect of reducing the amount of oxygen in the weld metal. Since F in the melt flux _{is added as a fluorine compound (F compound) such as CaF 2} , it is defined as a value obtained by converting the F compound in the melt flux into F in the present embodiment.

The F conversion value of the F compound per the total mass of the melt flux is 0% by mass or more, preferably 2% by mass or more, and more preferably 4% by mass or more.

On the other hand, if the F compound in the melt flux in terms of F exceeds 25% by mass, undercut and slag winding are likely to occur, and fluorinated gas is generated during welding to reduce the stability of the welding, so the total mass of the melt flux The F conversion value of the sugar F compound is 25% by mass or less, preferably 23% by mass or less, and more preferably 20% by mass or less.

<Al ₂ O ₃ : 10% by mass or more and 50% by mass or less>

Al ₂ O ₃ is a component having an effect of reducing the amount of oxygen in the weld metal while adjusting the viscosity and melting point of molten slag.

_{If the Al 2} O ₃ content in the melt flux is less than 10% by mass, it becomes difficult to obtain a sufficient deoxidation effect, so Al ₂ O _{3 per total mass of the melt flux} The content is 10% by mass or more, preferably 15% by mass or more.

On the other hand, if the Al ₂ O ₃ content in the melting flux exceeds 50% by mass, the viscosity of the molten slag increases, and there is a risk of poor penetration, so the Al ₂ O ₃ content per total mass of the melting flux is 48% by mass or less. And preferably 45% by mass or less.

On the other hand, in this embodiment, the content of all Al oxides in the melting flux _{is defined as a value converted to Al 2} O ₃ , and this converted value is simply _{described as the Al 2} O ₃ content.

<SiO ₂ : 35% by mass or less (including 0% by mass)>

SiO ₂ is an acidic component, and although it is a component that adjusts the viscosity and melting point of molten slag, it is also a component that makes it difficult to deoxidize the weld metal. In the present embodiment, it is possible to adjust the viscosity and melting point by the components other than SiO _2, it is not always necessary to contain SiO ₂ in the molten flux. That is, SiO ₂ is an optional component in the melt flux according to the present embodiment.

_{When SiO 2} is contained in the melting flux as an optional component _{, when the SiO 2} content exceeds 35% by mass, the viscosity of the molten slag increases, resulting in poor penetration, and the amount of oxygen in the weld metal increases, resulting in toughness. _{Therefore, the SiO 2} content per total mass of the melt flux is set to 35% by mass or less, and preferably 30% by mass or less.

On the other hand, in this embodiment, the content of all Si oxides in the melt flux _{is defined as a value converted to SiO 2} , and this converted value is simply _{described as the SiO 2} content.

<B ₂ O ₃ : 1.0 mass% or less (including 0 mass%)>

As described above, B is an element that improves the hardenability of the weld metal, and is an element that improves toughness by suppressing the growth of saltpeter ferrite. In particular, when the O content in the weld metal is about 0.0350 mass%, the effect is It is remarkable. However, when the O content in the weld metal is 0.0300% by mass or less and the metal structure is sufficiently refined, the influence of the B content on toughness is small. On the other hand, in order to stabilize the supply of B into the weld metal, it may be contained in the melting flux auxiliary. That is, B ₂ O ₃ is an optional component in the melt flux according to the present embodiment.

However, in the case where B is excessively added to the melt flux, the hardenability of the weld metal becomes excessive, so the toughness of the weld metal rather deteriorates due to the formation of island martensite, so B ₂ O _{3 in the melt flux} It is necessary to limit the content.

_{In the case where B 2} O ₃ is included in the melt flux as an optional component, _{if the B 2} O ₃ content in the melt flux exceeds 1.0 mass%, it becomes difficult to obtain stable toughness, so B ₂ O per total mass of the melt flux ₃ Content is 1.0 mass% or less, Preferably it is 0.5 mass% or less, More preferably, it is 0.3 mass% or less, More preferably, it is 0.25 mass% or less.

On the other hand, in this embodiment, the content of all B oxides in the melt flux _{is defined as a value converted to B 2} O ₃ , and this converted value is simply _{described as the B 2} O ₃ content.

Here, the melt flux according to the present embodiment contains 80 mass% or more in total of the above-described Ca conversion value, F conversion value, Al ₂ O ₃ , SiO ₂ and B ₂ O _3. It is preferable that this total is 85 mass% or more.

<Other ingredients>

The melt flux according to the present embodiment may contain flux components other than the above components, but the total of components other than the above components is preferably 12% by mass or less, and more preferably 8% by mass or less per total mass of the melt flux. It is preferable, and it is more preferable that it is 5 mass% or less.

On the other hand, as a flux component other than the above component, in addition to O contained in the Ca compound, there are TiO ₂ , MgO, MnO, FeO, and unavoidable impurities.

Here, when the melting flux contains MnO, when the MnO content is less than 10% by mass, the melting point and viscosity of the molten slag are appropriately maintained, and welding workability is improved. Further, in this case, since the amount of oxygen in the weld metal is also suppressed and toughness is improved, the MnO content per total mass of the melt flux is preferably less than 10% by mass, more preferably less than 5% by mass, and 1% by mass. It is more preferable to be less than.

<Method of manufacturing melting flux>

On the other hand, the melt flux according to the present embodiment described above is not particularly limited with respect to the manufacturing method or the like as long as the content of the component contained within the above range, and can be manufactured by a known method.

[3. Welding metal]

Further, the weld metal according to the present embodiment will be described. The weld metal according to the present embodiment is a weld metal obtained by electroslag welding using the above-described welding material, and when the content of each component is limited, excellent low-temperature toughness can be obtained. Hereinafter, the reasons for limiting the components and content in the weld metal will be described in detail.

The weld metal according to the present embodiment is a weld metal obtained by electroslag welding using the welding material described above,

Per total mass of weld metal,

C: 0.03 mass% or more and 0.08 mass% or less,

Si: 0.10 mass% or more and 0.40 mass% or less,

Mn: 1.0% by mass or more and 1.7% by mass or less,

Mo: 0.1% by mass or more and 0.8% by mass or less,

Ti: 0.001% by mass or more and less than 0.040% by mass,

Al: less than 0.019% by mass (not including 0% by mass),

B: less than 0.0045% by mass (not including 0% by mass),

O: less than 0.0300 mass% (including 0 mass%),

Cu: While being regulated to be less than 1.45% by mass (including 0% by mass),

The balance is Fe and unavoidable impurities.

<C: 0.03 mass% or more and 0.08 mass% or less>

C is an element that contributes to securing the strength of the weld metal by forming a solid solution or compound together with Fe.

If the C content in the weld metal is less than 0.03% by mass, the above action cannot be effectively exhibited, so the C content per total mass of the weld metal is set at 0.03% by mass or more, preferably 0.035% by mass or more.

On the other hand, if the C content in the weld metal exceeds 0.08% by mass, the number of compound particles increases, and since the Fe and C compound particles act as a starting point for void formation during the Charpy test, the low-temperature toughness of the weld metal Therefore, the C content per total mass of the weld metal is set to be 0.08% by mass or less, and preferably 0.075% by mass or less.

<Si: 0.10% by mass or more and 0.40% by mass or less>

Since Si is a deoxidation element, Si is added to the weld metal, thereby reducing the oxygen concentration in the weld metal and improving the low-temperature toughness.

If the Si content in the weld metal is less than 0.10 mass%, the above action cannot be effectively exhibited, so the Si content per total mass of the weld metal is 0.10 mass% or more, preferably 0.12 mass% or more.

On the other hand, when the Si content in the weld metal exceeds 0.40 mass%, the strength of the weld metal becomes excessive and the low-temperature toughness decreases, so the Si content per total mass of the weld metal is 0.40 mass% or less, preferably 0.35 mass%. It should be as follows.

<Mn: 1.0% by mass or more and 1.7% by mass or less>

Mn is an element that contributes to securing the strength of the weld metal by solid solution strengthening with Fe.

If the content of Mn in the weld metal is less than 1.0% by mass, the above action cannot be effectively exhibited, so the Mn content per total mass of the weld metal is set at 1.0% by mass or more, preferably at least 1.1% by mass.

On the other hand, if the Mn content in the weld metal exceeds 1.7% by mass, the strength of the weld metal becomes excessive and the low-temperature toughness decreases, so the Mn content per total mass of the weld metal is 1.7% by mass or less, preferably 1.6% by mass. It should be as follows.

<Mo: 0.1% by mass or more and 0.8% by mass or less>

Mo is an element that contributes to securing the strength of the weld metal by solid solution strengthening with Fe.

When the Mo content in the weld metal is less than 0.1% by mass, the above action cannot be effectively exhibited, so the Mn content per total mass of the weld metal is set at 0.1% by mass or more, preferably 0.2% by mass or more.

On the other hand, when the Mo content in the weld metal exceeds 0.8% by mass, the strength of the weld metal becomes excessive and the low-temperature toughness decreases, so the Mo content per total mass of the weld metal is 0.8% by mass or less, preferably 0.7% by mass. It should be as follows.

<Ti: 0.001% by mass or more and less than 0.040% by mass>

Ti is an element necessary for preventing formation of coarse grain boundary ferrite in the weld metal as a Ti oxide, which serves as a nucleus that generates acyclic ferrite.

If the Ti content in the weld metal is less than 0.001% by mass, the amount of Ti oxide for producing acyclic ferrite is insufficient, and the effect of improving the toughness of the weld metal cannot be obtained, so the Ti content per total mass of the weld metal is 0.001% by mass. The above, preferably 0.002% by mass or more, and more preferably 0.003% by mass or more.

On the other hand, when the Ti content in the weld metal is 0.040% by mass or more, the Ti precipitates in the weld metal are excessively large, and the toughness of the weld metal is rather lowered. Is less than 0.035 mass%, more preferably less than 0.030 mass%.

<Al: less than 0.019% by mass (not including 0% by mass)>

Since Al is a deoxidation element, by containing Al in the weld metal, it is an element that lowers the oxygen concentration in the weld metal and improves the low-temperature toughness of the weld metal.

However, as described above, for the purpose of further reducing the amount of oxygen in the weld metal, when Al in the weld metal, which is a deoxidation element, is contained in excess, coarse inclusions are formed in the metal structure of the weld metal, rather than welding. Since the toughness of the metal is lowered, the Al content per total mass of the weld metal is less than 0.019 mass%, preferably less than 0.018 mass%, and more preferably less than 0.016 mass%.

<B: less than 0.0045 mass% (0 mass% is not included)>

B is an element that improves the hardenability of the weld metal, and is an element that improves toughness by suppressing the growth of saltpeter ferrite.

However, for the purpose of improving the toughness of the weld metal, if B in the weld metal is contained excessively, the hardenability of the weld metal becomes excessive, and therefore the toughness of the weld metal is rather due to the formation of island martensite. Because of this deterioration, the B content per total mass of the weld metal is less than 0.0045 mass%, preferably less than 0.0040 mass%, and more preferably less than 0.0035 mass%.

<O: less than 0.0300% by mass (including 0% by mass)>

When the O content in the weld metal increases, inclusions that become oxides increase. As a result, since the cleanliness of the weld metal decreases and toughness also decreases, it is preferable to reduce the O content in the weld metal as much as possible.

When the O content per total mass of the weld metal is less than 0.0300 mass%, a weld metal excellent in toughness can be obtained. The O content per total mass of the weld metal is preferably less than 0.025 0 mass%, more preferably less than 0.0200 mass%.

<Cu: less than 1.45% by mass (including 0% by mass)>

Cu is an element that contributes to the strength.

However, if the Cu content is too large, the strength may deteriorate, so the Cu content per total mass of the weld metal is less than 1.45% by mass, preferably less than 1.0% by mass, and more preferably less than 0.5% by mass. .

<balance>

The balance of the weld metal according to this embodiment is Fe and unavoidable impurities. Examples of inevitable impurities include Ni, P, S, Cr, V, Nb, Sn, Zr, and N. For example, Ni is 1.5% by mass or less, P and S are each 0.05% by mass or less, Cr is 1.5% by mass or less, V and Nb are each 0.10% by mass or less, Sn and Zr are each 0.010% by mass or less, N is It may be contained in an amount of 0.010% by mass or less.

[4. Electroslag welding method]

The electroslag welding method according to the present embodiment relates to the electroslag welding method of welding using the welding material described above. On the other hand, welding conditions and the like in electroslag welding are not particularly limited, and welding can be performed by a known method.

Example

Hereinafter, although an invention example and a comparative example are given and this invention is demonstrated in more detail, this invention is not limited to this.

As shown in Fig. 1, the width of the improvement surrounded by the backing material (the rear side of the improvement) and the sliding copper backing plate (the surface side of the improvement) was 10 mm, and 20° V improvement welding was performed.

The components (% by mass) of the base material are shown in Table 1 below. On the other hand, the content of each chemical component shown in Table 1 is the content (mass%) per total mass of the base material. In addition, the balance is Fe and unavoidable impurities. In addition, in Table 1, the notation "-" in each component composition means that it is below the detection limit value in a composition analysis.

Then, electroslag welding was performed under the welding conditions shown in Table 2 below, using an electroslag welding wire having a wire diameter of 1.6 mm. On the other hand, the melting flux was added so that the depth of the slag bath was 25 mm.

The sheet thickness (mm) and root gap (mm) of the base material used in each of the invention examples and comparative examples, and the composition of the melting flux and the composition of the electroslag welding wire are summarized in Table 3 below. The balance of the composition of the electroslag welding wire contains 95 to 98% by mass of Fe. In addition, the composition of the obtained weld metal is shown in Table 4 below.

On the other hand, the content of each chemical component shown in Tables 3 and 4 is the content (mass%) per total mass of the flux for the melt flux, and the content per total mass of the wire for the electroslag welding wire (mass%), and welding About the metal, it is the content (mass %) per the total mass of the weld metal. In addition, the balance in the wire for electroslag welding and the weld metal is Fe and unavoidable impurities. In addition, in Table 3, the notation "-" in each component composition means that it is below the detection limit value in a composition analysis.

After completion of welding, a Charpy impact test piece and a tensile test piece were taken from the obtained weld metal, and the toughness and strength of the weld metal were evaluated. The test methods of the Charpy impact test and the tensile test are shown below.

<Charpy impact test>

The collected test piece was subjected to a Charpy impact test at -20°C in accordance with JIS Z2242 to measure the absorbed energy vE-20°C (J) to evaluate the toughness of the weld metal. The test piece was collected at three places, and the average value was calculated. On the other hand, a weld metal having an absorbed energy of 115 J or more obtained by measurement was evaluated as having good toughness.

<Tensile test>

About the sampled test piece, 0.2% proof stress (MPa) and tensile strength (MPa) were measured by performing a tensile test according to JIS Z2241, and the strength of a weld metal was evaluated.

The measurement results of the Charpy impact test and the tensile test are summarized in Table 5 below.

As shown in Tables 3 to 5 above, Inventive Example No. In 1 to 13, since the component content of the wire for electroslag welding and the melt flux contained in the welding material is within the range of the present invention, a weld metal having excellent low-temperature toughness could be obtained. In addition, regarding the tensile strength, a high strength suitable for electroslag welding of a high-tensile steel sheet of 500 MPa or more was obtained.

On the other hand, Comparative Example No. In 14 and 21, since the B content in the wire exceeds the upper limit of the range of the present invention, the B content in the weld metal also exceeds the upper limit of the range of the present invention, and the toughness of the weld metal is low.

Comparative Example No. In 15 and 16, since the Al content in the wire exceeds the upper limit of the range of the present invention, the Al content in the weld metal also exceeds the upper limit of the range of the present invention, and the toughness of the weld metal is low.

Comparative Example No. 17-20 and No. In values 22 to 27, since the Ti content and B content in the wire exceeded the upper limit of the range of the present invention, the B content in the weld metal also exceeded the upper limit of the range of the present invention, and the toughness of the weld metal became low.

In addition, Comparative Example No. Fig. 28 is an example in which electrogas arc welding is performed, without using a flux, and the C content in the wire exceeds the upper limit of the scope of the present invention, and the B content in the weld metal exceeds the upper limit of the scope of the present invention. Therefore, the toughness of the weld metal became low.

Comparative Example No. Since 29-31 _{does not contain Al 2} O ₃ in the flux and is less than the lower limit of the range of the present invention, a sufficient deoxidation effect cannot be obtained with respect to the weld metal, and the O content in the weld metal exceeds the upper limit of the range of the present invention. Because it exceeded, the toughness of the weld metal became low.

Comparative Example No. At 32, since the Cu content in the wire exceeds the upper limit of the range of the present invention, the Cu content in the weld metal also exceeds the upper limit of the range of the present invention, and the toughness of the weld metal is low.

Claims (4)

As a welding material used for electroslag welding,
Electroslag welding wire,
Per total mass of wire,
Fe: 94% by mass or more,
C: 0.01% by mass or more and 0.05% by mass or less,
Si: 0.05% by mass or more and 0.40% by mass or less,
Mn: 1.0% by mass or more and 1.8% by mass or less,
Mo: 0.1% by mass or more and 0.8% by mass or less,
Ti: 0.01% by mass or more and less than 0.08% by mass,
Al: less than 0.06 mass% (including 0 mass%),
B: less than 0.0070 mass% (including 0 mass%),
Cu: It is regulated to be less than 1.5% by mass (including 0% by mass),
Melt flux,
Per total mass of flux,
Ca compound value in terms of Ca: 10% by mass or more and 45% by mass or less,
F conversion value of the compound F: 0% by mass or more and 25% by mass or less,
Al ₂ O ₃ : contains 10% by mass or more and 50% by mass or less,
SiO ₂ : 35 mass% or less (including 0 mass%),
B ₂ O ₃ : It is regulated to 1.0% by mass or less (including 0% by mass),
A welding material, characterized in that the electroslag welding wire and the molten flux are used in combination. The method of claim 1,
The melt flux is,
Per total mass of flux,
MnO: A welding material characterized in that it is regulated to be less than 10% by mass (including 0% by mass). As a weld metal obtained by electroslag welding using the welding material according to claim 1 or 2,
Per total mass of weld metal,
C: 0.03 mass% or more and 0.08 mass% or less,
Si: 0.10 mass% or more and 0.40 mass% or less,
Mn: 1.0% by mass or more and 1.7% by mass or less,
Mo: 0.1% by mass or more and 0.8% by mass or less,
Ti: 0.001% by mass or more and less than 0.040% by mass,
Al: less than 0.019% by mass (not including 0% by mass),
B: less than 0.0045% by mass (not including 0% by mass),
O: less than 0.0300 mass% (including 0 mass%),
Cu: While being regulated to be less than 1.45% by mass (including 0% by mass),
Weld metal, characterized in that the balance is Fe and unavoidable impurities. An electroslag welding method for welding using the welding material according to claim 1 or 2.

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