JP7564079B2 - Ni-based alloy covered metal arc welding rod - Google Patents

Description

The present invention relates to a Ni-based alloy covered metal arc welding rod.

Traditionally, 9% Ni steel, which has high strength and toughness, has been widely used in storage tanks for liquefied natural gas (LNG). In order to manufacture structures using 9% Ni steel, various Ni-based alloy covered metal arc welding rods have been proposed that can produce weld metal with excellent strength and toughness.

For example, Patent Document 1 discloses a Ni-based alloy covered metal arc welding rod in which the contents of Ni, Cr, C, Si, Nb, Cu, N, and H in the core wire are controlled, and the H content in the coating is also controlled. Patent Document 1 describes that by incorporating appropriate contents of Ti, Al, Zr, V, and B in the core wire, it is possible to reduce oxygen in the weld metal and suppress the occurrence of blowholes.

Furthermore, Patent Document 2 discloses a Ni-based alloy covered metal arc welding rod in which the C, Si, Mn, Mg, etc. in the core wire are controlled, and the total content of Mn, Cr, Mo, Nb, Ta, W, Ni, Co, and Fe, the total content of Ti, Al, and Mg, and the Si content, etc. in the coating are controlled. Patent Document 2 describes that a weld metal with excellent mechanical properties and low occurrence of porosity defects can be obtained.

Japanese Unexamined Patent Publication No. 169192/1983 Patent No. 6296550

However, the Ni-based alloy covered metal arc welding rods described in Patent Documents 1 and 2 above have not been examined for their moisture absorption resistance. In covered metal arc welding rods, there is a problem that the coating absorbs moisture and if the amount of moisture relative to the total mass of the welding rod is high, blowholes will form in the weld metal. Furthermore, blowholes formed in the weld metal may reduce the mechanical properties of the weld metal.

The present invention was made in consideration of the above-mentioned circumstances, and aims to provide a Ni-based alloy covered metal arc welding rod that has excellent moisture absorption resistance of the coating material and can suppress the occurrence of blowholes during welding.

As a result of thorough investigation into the above-mentioned problems of Ni-based alloy covered metal arc welding electrodes, the inventors have found that the inclusion of Li in the coating is effective in improving moisture absorption resistance, and have confirmed that K contained in the coating particularly deteriorates moisture absorption resistance. The inventors have then found that by controlling Li, Na, and K within specific ranges and controlling the ratio of Li to K in the coating within a specific range, it is possible to improve moisture absorption resistance and suppress the occurrence of blowholes during welding. The present invention has been made based on these findings, and the above-mentioned object of the present invention is achieved by the following configuration [1] relating to Ni-based alloy covered metal arc welding electrodes.

[1] A Ni-based alloy covered metal arc welding rod in which a core wire is covered with a coating material,
With respect to the total mass of the Ni-based alloy covered metal arc welding rod,
_SiO2 : 1% by mass or more and 7% by mass or less,
_CO2 : 2.5% by mass or more and 7.0% by mass or less,
F: 0.5% by mass or more and 5.0% by mass or less; and Ni: 40% by mass or more,
Either or _both of _TiO2 and _Al2O3 ,
TiO ₂ : more than 0 mass % and not more than 2.0 mass %; and Al ₂ O ₃ : more than 0 mass % and not more than 2.0 mass %,
The coating agent contains, based on the total mass of the coating agent,
Li: 0.3% by mass or more and 1.2% by mass or less,
Na: 0.5% by mass or more and 1.5% by mass or less; and K: 0.6% by mass or more and 1.8% by mass or less;
When the Li content in the coating agent is expressed as [Li] in mass% relative to the total mass of the coating agent, and the K content in the coating agent is expressed as [K] in mass% relative to the total mass of the coating agent,
A Ni-based alloy covered metal arc welding rod, characterized in that [Li]/[K] is 0.15 or more and 1.4 or less.

Furthermore, preferred embodiments of the present invention relating to Ni-based alloy covered metal arc welding rods relate to the following [2] to [5].

[2] The Ni-based alloy covered metal arc welding rod described in [1], characterized in that the coating rate of the coating agent is 20% by mass or more and 60% by mass or less.

[3] Furthermore, with respect to the total mass of the Ni-based alloy covered metal arc welding rod,
The Ni-based alloy covered metal arc welding rod according to [1] or [2], characterized in that C is 1.0 mass% or less.

[4] Furthermore, with respect to the total mass of the Ni-based alloy covered metal arc welding rod,
Al: more than 0% by mass and not more than 2.0% by mass,
Ti: more than 0% by mass and not more than 2.0% by mass,
Mg: more than 0% by mass and not more than 0.5% by mass, and
The Ni-based alloy covered metal arc welding rod according to any one of [1] to [3], characterized in that it contains at least one selected from Fe: more than 0 mass% and 12.0 mass% or less.

[5] Furthermore, with respect to the total mass of the Ni-based alloy covered metal arc welding rod,
Cr: more than 0% by mass and not more than 20.0% by mass,
Mo: more than 0% by mass and not more than 15.0% by mass,
W: more than 0% by mass and not more than 5.0% by mass,
Mn: more than 0% by mass and not more than 5.0% by mass, and
The Ni-based alloy covered metal arc welding rod according to any one of [1] to [4], characterized in that it contains at least one selected from Nb: more than 0 mass% and 5.0 mass% or less.

The present invention provides a Ni-based alloy covered metal arc welding rod that has excellent moisture absorption resistance of the coating material and can suppress the occurrence of blowholes during welding.

Hereinafter, the embodiment for carrying out the present invention will be described in detail. Note that the present invention is not limited to the embodiment described below, and can be carried out with any modification within the scope of the gist of the present invention.
Hereinafter, the Ni-based alloy covered metal arc welding rod according to this embodiment will be described.

[Shielded metal arc welding electrodes]
The covered metal arc welding rod according to the present embodiment is a Ni-based alloy covered metal arc welding rod in which a core wire is covered with a coating material. The core wire is made of, for example, pure Ni or a Ni-based alloy. The Ni-based alloy covered metal arc welding rod is a welding rod in which the component of the deposited metal is a Ni-based alloy. Hereinafter, the Ni-based alloy covered metal arc welding rod is also simply referred to as a "covered metal arc welding rod."

The reasons for adding and limiting the numerical values of the components contained in the coating material and the coated metal arc welding rod of this embodiment are explained in detail below. In the following explanation, the content of Li, Na, and K in the coating material is defined as the content relative to the total mass of the coating material. The other components are defined as the total content of the components contained in the core wire and coating material relative to the total mass of the coated metal arc welding rod (the total amount of the core wire and coating material).

(Li: 0.3% by mass or more and 1.2% by mass or less)
Li has the effect of improving the moisture absorption resistance of the coating agent. If the Li content in the coating agent is less than 0.3 mass %, the effect of improving the moisture absorption resistance cannot be obtained. Therefore, The Li content in the coating agent is 0.3 mass% or more, preferably 0.35 mass% or more, and more preferably 0.4 mass% or more, based on the total mass of the coating agent. If the Li content in the coating agent exceeds 1.2 mass %, the viscosity of the coating agent decreases, making the coating operation difficult in the coating step. If the Li content exceeds 1.2 mass %, the coating agent is likely to fall off after coating and cracks are likely to occur during drying. % or less, preferably 1.0% or less by mass, and more preferably 0.9% or less by mass.

In the case of the covered metal arc welding rod according to this embodiment, in order to improve the moisture absorption resistance of the coating, it is important to control the Li content in the coating that covers the core wire, rather than the Li content in the entire covered metal arc welding rod, so the Li content in the coating is specified. For the same reason, the contents of Na and K, which will be described later, in the coating are also specified. Li is contained in the coating in the form of compounds such as carbonates, oxides, and fluorides. In this embodiment, the Li content refers to the total Li content in the coating.

(Na: 0.5% by mass or more and 1.5% by mass or less)
Na is a component that has the effect of ensuring the adhesion of the coating material and the arc stability. In addition, by controlling the Na content in the coating material within a predetermined range, the moisture absorption resistance of the coating material is improved. If the Na content in the coating material is less than 0.5 mass %, the arc becomes unstable, and the coating material is likely to fall off after coating and to undergo drying cracks during drying. Therefore, the Na content in the coating agent is set to 0.5 mass % or more, preferably 0.6 mass % or more, and more preferably 0.8 mass % or more, based on the total mass of the coating agent. On the other hand, if the Na content in the coating agent exceeds 1.5 mass %, the moisture absorption resistance of the coating agent deteriorates. Therefore, the Na content in the coating agent is set to 1.5 mass % or less relative to the total mass of the coating agent. It is 0.5 mass% or less, preferably 1.3 mass% or less, and more preferably 1.2 mass% or less.

Na is contained in the coating agent in the form of compounds such as fluorides and oxides. In this embodiment, the Na content refers to the total content of Na contained in the coating agent.

(K: 0.6% by mass or more and 1.8% by mass or less)
Like Na, K is a component that has the effect of ensuring the adhesion of the coating material and the arc stability. In addition, by controlling the K content in the coating material within a predetermined range, If the K content in the coating is less than 0.6 mass %, the arc becomes unstable, and the coating falls off after coating and drying cracks occur during drying. Therefore, the K content in the coating agent is set to 0.6 mass% or more, preferably 0.65 mass% or more, and more preferably 0.7 mass% or more, based on the total mass of the coating agent. On the other hand, if the K content in the coating agent exceeds 1.8 mass %, the moisture absorption resistance of the coating agent is deteriorated. Therefore, the K content in the coating agent is preferably 1.8 mass % or more. The content is 1.8% by mass or less, preferably 1.3% by mass or less, and more preferably 1.0% by mass or less.

K is contained in the coating agent in the form of compounds such as fluorides and oxides. In this embodiment, the K content refers to the total K content contained in the coating agent.

([Li]/[K]: 0.15 or more and 1.4 or less)
Among the components in the coating agent, Li and K are components that have a particularly large effect on moisture absorption resistance, with Li improving the moisture absorption resistance and K decreasing the moisture absorption resistance. Therefore, in this embodiment, In the method, the moisture absorption resistance of the coating agent is improved by appropriately controlling the ratio of the Li content to the K content in the coating agent.

When the Li content in the coating agent is expressed as [Li] in mass% relative to the total mass of the coating agent, and the K content in the coating agent is expressed as [K] in mass% relative to the total mass of the coating agent, if the value obtained from the formula ([Li]/[K]) is less than 0.15, the moisture absorption resistance of the coating agent decreases. Therefore, the value obtained from the formula ([Li]/[K]) is 0.15 or more, preferably 0.20 or more, and more preferably 0.30 or more.
On the other hand, if the value obtained by the formula ([Li]/[K]) exceeds 1.4, the adhesion strength of the coating agent decreases, and the coating properties such as drying cracks decrease. In addition, the arc becomes weak and unstable. Therefore, the value obtained by the formula ([Li]/[K]) is set to 1.4 or less, preferably 1.2 or less, and more preferably 1.1 or less.

As mentioned above, the content of Li, Na, and K in the coating is important, but the components shown below may be contained in the coating or in the core wire if they are contained in the covered metal arc welding rod. The Ni-based alloy covered metal arc welding rod according to this embodiment can use either pure Ni or Ni-based alloy as the core wire, so when a core wire made of pure Ni is used, components other than Ni will be contained in the coating.

( _SiO2 : 1% by mass or more and 7% by mass or less)
_SiO2 is a component that is mainly contained in the coating agent and acts as a binder and a slag-forming agent, as well as a deoxidizing agent.
If the _SiO2 content in the covered metal arc welding rod is less than 1 mass%, the effect as a binder cannot be obtained, and the effect as a deoxidizer is also insufficient. The _SiO2 content in the rod is 1 mass% or more, preferably 2 mass% or more, and more preferably 3 mass% or more, based on the total mass of the covered arc welding rod. If the _SiO2 content in the welding rod exceeds 7 mass%, the slag becomes glassy and the slag peelability deteriorates. Therefore, the _SiO2 content in the covered metal arc welding rod is The content is 7% by mass or less, preferably 6.5% by mass or less, and more preferably 6% by mass or less, based on the total mass of the rod.
In this embodiment, the _SiO2 content is a converted value of all Si contained in the coating material and the core wire converted into _SiO2 .

( _CO2 : 2.5% by mass or more and 7.0% by mass or less)
Metal carbonates have the effect of shielding the arc with gas generated by high-temperature decomposition, and obtaining sound weld metal. In addition, by including metal carbonates in the covered electrode, the fluidity of the slag is improved. In this embodiment, examples of the metal carbonate include BaCO ₃ , CaCO ₃ , and Li ₂ CO ₃ . In this embodiment, the metal carbonate is All metal carbonates are defined as _CO2 content calculated as _CO2 .

If the _CO2 content is less than 2.5 mass%, sound weld metal and good welding workability cannot be obtained. Therefore, the _CO2 content in the covered metal arc welding rod is 2.5 mass% or more, preferably 3.0 mass% or more, and more preferably 3.2 mass% or more, based on the total mass of the covered metal arc welding rod. On the other hand, if a large amount of _CO2 is contained, slag removability and bead appearance are deteriorated. Therefore, the _CO2 content in the covered metal arc welding rod is 7.0 mass% or less, preferably 6.5 mass% or less, and more preferably 6.0 mass% or less, based on the total mass of the covered metal arc welding rod.

(F: 0.5% by mass or more and 5.0% by mass or less)
F is a component that increases the arc strength and lowers the viscosity and solidification temperature of the slag to improve its fluidity, thereby improving the slag removability, preventing incomplete fusion, and preventing pits and blowholes.
If the F content in the covered electrode is less than 0.5 mass %, the above-mentioned effect cannot be sufficiently obtained. Therefore, the F content in the covered electrode is set to 100% by mass of the total mass of the covered electrode. The F content in the covered metal arc welding rod is set to 0.5 mass % or more, preferably 1.0 mass % or more, and more preferably 1.5 mass % or more. If the F content exceeds 0 mass %, the arc strength becomes too strong, which increases spattering, and undercutting is likely to occur, resulting in a convex bead shape. The content is 5.0 mass % or less, preferably 4.0 mass % or less, and more preferably 3.5 mass % or less, based on the total mass of the welding rod.
In addition, F is contained in the covered electrode in the form of metal fluorides such as CaF ₂ and LiF. In this embodiment, the F content refers to the total F content contained in the covered electrode. It means quantity.

(Ni: 40% by mass or more)
In the Ni-based alloy covered metal arc welding rod of this embodiment, Ni is a main component, and has the effect of forming a stable austenitic structure in the weld metal and ensuring toughness at extremely low temperatures. If the Ni content is less than 40 mass%, the austenitic structure cannot be maintained when the base metal is diluted, and the toughness may decrease. The Ni content in the covered metal arc welding rod is 40 mass% or more, preferably 43 mass% or more, and more preferably 45 mass% or more, based on the total mass of the welding rod. The content is preferably 80% by mass or less, more preferably 65% by mass or less, and even more preferably 60% by mass or less.

( _TiO2 : more than 0% by mass and not more than 2.0% by mass)
( _Al2O3 : more than 0% by mass _and 2.0% by mass or less)
_{TiO2 and Al2O3} are components that act as slag forming agents, but the covered metal arc welding rod of the present embodiment may contain either _TiO2 or _{Al2O3 .} If the total content of _{TiO2 and Al2O3} is 0 mass%, the viscosity of the slag decreases and the bead shape deteriorates. In the above, either or _both of _TiO2 and _Al2O3 are contained in an amount exceeding 0 mass% based on the total mass of the covered electrode, and the _TiO2 content and the _Al2O3 content are The O ₃ content is preferably 0.05 mass% or more, and more preferably 0.10 mass% or more. On the other hand, the TiO ₂ and Al ₂ O ₃ contents are each 2.0 mass% or more. %, the slag becomes glassy and the slag removability deteriorates. Therefore, the contents of _{TiO2 and Al2O3} in the covered metal arc welding rod are each set to 2.0 mass% or less, and preferably 1.5 mass% or less, based on the total mass of the covered metal arc welding rod. In _the present embodiment, _TiO2 is the _TiO2 equivalent of an acid-insoluble Ti compound, and _Al2O3 is the Al compound insoluble in acid, more preferably 1.0 mass% or less. This is _{an Al2O3} converted value.

In the covered metal arc welding rod of this embodiment, Cr, Mo, Fe, W, Mn, Al, Ti, Nb, and Mg are not essential components, but Al, Ti, Mg, and Fe are components that affect the toughness of the weld metal, and at least one selected from Al, Ti, Mg, and Fe may be contained in the covered metal arc welding rod in the content ranges shown below. In addition, Cr, Mo, W, Mn, and Nb are components that can realize solid solution strengthening of the weld metal, and at least one selected from Cr, Mo, W, Mn, and Nb may be contained in the covered metal arc welding rod in the content ranges shown below.

(Cr: more than 0 mass% and 20.0 mass% or less)
Cr is a metal component contained in a covered metal arc welding electrode for the purpose of strengthening the solid solution of the weld metal and strengthening the corrosion resistance. It is not always necessary for a covered metal arc welding electrode to contain Cr, but it is preferable to use a covered metal arc welding electrode. The Cr content in the arc welding rod is preferably more than 0 mass%, more preferably 1.0 mass% or more, and more preferably 7.0 mass% or more, based on the total mass of the covered metal arc welding rod. On the other hand, when the Cr content in the covered metal arc welding rod is 20.0 mass % or less, the toughness of the weld metal can be improved. is preferably 20.0 mass % or less, more preferably 15.0 mass % or less, based on the total mass of the covered electrode.

(Mo: more than 0 mass% and 15.0 mass% or less)
Mo, like Cr, is a metal component contained in a covered metal arc welding electrode for the purpose of strengthening the solid solution of the weld metal and improving the corrosion resistance. It is not always necessary to contain Mo in a covered metal arc welding electrode. Although not required, the Mo content in the covered metal arc welding rod is preferably more than 0 mass % and more preferably 1.0 mass % or more based on the total mass of the covered metal arc welding rod; On the other hand, when the Mo content in the covered metal arc welding electrode is 15.0 mass % or less, the strength of the weld metal can be prevented from becoming excessive and the toughness can be improved. Therefore, the Mo content in the covered metal arc welding rod is preferably 15.0 mass % or less, and more preferably 10.0 mass % or less, based on the total mass of the covered metal arc welding rod.

(Fe: more than 0 mass% and 12.0 mass% or less)
Fe dissolves in Ni and is effective in improving the ductility of the weld metal, but adding too much Fe reduces the low-temperature toughness. It is not always necessary to include Fe in a covered arc welding rod, but it is recommended to add Fe to a covered arc welding rod. The Fe content in the welding rod is preferably more than 0 mass%, more preferably 1.0 mass% or more, and more preferably 3.0 mass% or more, based on the total mass of the covered metal arc welding rod. On the other hand, when the Fe content in the covered metal arc welding rod is 12.0 mass % or less, the deterioration of the toughness of the weld metal can be prevented. Therefore, the Fe content in the covered metal arc welding rod is The content is preferably 12.0 mass % or less, and more preferably 10.0 mass % or less, based on the total mass of the covered electrode.

(W: more than 0 mass% and 5.0 mass% or less)
W, like Cr, is a metal component contained in a covered electrode for the purpose of strengthening the solid solution of the weld metal and improving the corrosion resistance. A covered electrode does not necessarily contain W. Although it is not necessary to make the electrode 100% by mass, the W content in the electrode 100% by mass is preferably more than 0% by mass, and more preferably 0.3% by mass or more, based on the total mass of the electrode 100% by mass. When the W content in the covered metal arc welding electrode is 5.0 mass % or less, the desired toughness of the weld metal can be ensured. The content is preferably 5.0 mass % or less, and more preferably 2.0 mass % or less, based on the total mass of the welding rod.

(Mn: more than 0 mass% and 5.0 mass% or less)
Mn is a metal component added to a covered metal arc welding rod to strengthen the weld metal and as a deoxidizer. It is not always necessary to include Mn in a covered metal arc welding rod, but it is recommended to add Mn to a covered metal arc welding rod. The Mn content in the welding rod is preferably more than 0 mass% and more preferably 1.0 mass% or more based on the total mass of the covered metal arc welding rod. When the Mn content is 5.0 mass % or less, the viscosity of the molten metal is prevented from decreasing, and the welding workability can be improved. It is preferably 5.0% by mass or less, and more preferably 3.0% by mass or less.

(Nb: more than 0 mass% and 5.0 mass% or less)
Nb is a metal component added to a covered metal arc welding rod for the purpose of solid solution strengthening of the weld metal. It is not always necessary to include Nb in a covered metal arc welding rod, but it is preferable to add Nb to a covered metal arc welding rod. The Nb content in the covered metal arc welding rod is preferably more than 0 mass% and more preferably 1.0 mass% or more based on the total mass of the covered metal arc welding rod. When the Nb content is 5.0 mass% or less, the hot cracking resistance of the weld metal can be improved. Therefore, the Nb content in the covered metal arc welding rod is 5.0 mass% or less with respect to the total mass of the covered metal arc welding rod. It is preferable that the content of the water-soluble polymer is 0.01 to 0.1 mass %, and more preferably 0.01 to 0.1 mass %.

(Al: more than 0% by mass and 2.0% by mass or less)
Since Al is a deoxidizer and is an ingredient that has the effect of reducing the amount of oxygen in the weld metal and improving the toughness, it is preferable to contain Al in the covered metal arc welding rod. Although it is not necessary for the covered electrode to contain Al, the Al content in the covered electrode is preferably more than 0 mass% and more preferably 0.3 mass% or more based on the total mass of the covered electrode. On the other hand, when the Al content in the covered metal arc welding electrode is 2.0 mass % or less, good impact performance of the weld metal can be maintained, and the ductility and durability of the weld metal can be improved. Therefore, the Al content in the covered metal arc welding rod is preferably 2.0 mass% or less, and more preferably 1.8 mass% or less, based on the total mass of the covered metal arc welding rod. It is more preferable that the content of Al is not more than 100%. In the present embodiment, the Al content refers to the content of Al contained in simple Al or in an Al alloy.

(Ti: more than 0 mass% and 2.0 mass% or less)
Like Al, Ti is a deoxidizer and is an ingredient that has the effect of reducing the amount of oxygen in the weld metal and improving toughness, so it is preferable to include Ti in the covered metal arc welding rod. Although it is not necessary for the arc welding rod to contain Ti, the Ti content in the covered metal arc welding rod is preferably more than 0 mass% based on the total mass of the covered metal arc welding rod, and more preferably less than 0.1 mass%. On the other hand, when the Ti content in the covered electrode is 2.0 mass % or less, good impact performance of the weld metal can be maintained and the weld metal can be easily formed. Therefore, the Ti content in the covered metal arc welding rod is preferably 2.0 mass% or less, and more preferably 1.0 mass% or less, based on the total mass of the covered metal arc welding rod. In the present embodiment, the Ti content refers to the content of Ti contained in simple Ti or Ti alloy.

(C: 1.0% by mass or less)
When the C content in the covered electrode is 1.0 mass % or less, the occurrence of porosity defects can be suppressed. Therefore, the C content in the covered electrode is 1.0 mass % or less based on the total mass of the covered electrode. The C content in the covered electrode is preferably 1.0 mass % or less, more preferably 0.08 mass % or less, and further preferably 0.07 mass % or less. Since C is inevitably mixed in, the lower limit is substantially 0.0005 mass %. In this embodiment, the C content is the C content excluding C contained in oxides.

(Mg: more than 0% by mass and 0.5% by mass or less)
Like Al, Mg is a deoxidizer and is an ingredient that has the effects of reducing the amount of oxygen in the weld metal and improving toughness. Therefore, it is preferable to include Mg in the covered metal arc welding electrode. Although it is not necessary for the covered metal arc welding rod to contain Mg, the Mg content in the covered metal arc welding rod is preferably more than 0 mass% based on the total mass of the covered metal arc welding rod. When the Mg content in the covered electrode is 0.5 mass % or less, the deterioration of the slag removability can be suppressed. It is preferably 0.5% by mass or less, and more preferably 0.4% by mass or less.

(Ca: 2% by mass or more and 10% by mass or less)
The covered metal arc welding rod according to the present embodiment contains Ca contained in carbonates, metal fluorides, etc., as a component other than the above components. The Ca content in the covered metal arc welding rod is It is preferably 2% by mass or more and 10% by mass or less based on the total mass of the rod.

(Ba: 0 mass% or more and 5 mass% or less)
The covered metal arc welding rod according to the present embodiment may contain Ba carbonate as the carbonate. The Ba content of the covered metal arc welding rod is 0 mass% or more and 5 mass% or less with respect to the total mass of the covered metal arc welding rod. It can be said that:
The total amount of Ca and Ba in the covered metal arc welding rod is preferably 4 mass % or more and 12 mass % or less based on the total mass of the covered metal arc welding rod.

( _ZrO2 : 0 mass% or more and 2.0 mass% or less)
The Ni-based alloy covered metal arc welding rod according to the present embodiment may contain _ZrO2 as a slag forming agent. The _ZrO2 content in the covered metal arc welding rod is, based on the total mass of the covered metal arc welding rod, In the present embodiment, _ZrO2 is the _ZrO2 equivalent value of all Zr contained in the covered metal arc welding rod.

In this embodiment, when the covered metal arc welding rod does not contain Cr, Mo, Mn, Nb, Fe, or W, the total content of SiO ₂ , CO ₂ , F, Ni, TiO ₂ , and Al ₂ O ₃ is preferably 80 mass% or more, more preferably 85 mass% or more, and preferably 90 mass% or more, based on the total mass of the covered metal arc welding rod. When the covered metal arc welding rod of this embodiment contains one or more of Cr, Mo, Mn, Nb, Fe, and W, the total content of SiO ₂ , CO ₂ , F, Ni, TiO ₂ , Al ₂ O _{3 ,} Cr, Mo, Mn, Nb, Fe, and W is preferably 80 mass% or more, 85 mass% or more, or 90 mass% or more.

<Inevitable impurities>
The covered metal arc welding rod according to the present embodiment contains inevitable impurities, and examples of the inevitable impurities include V, Cu, P, S, B, Zr, Ta, Co, H, and N. The inevitable impurities in the covered metal arc welding rod are preferably restricted to 0.5 mass% or less of each of the inevitable impurities with respect to the total mass of the covered metal arc welding rod.

<Coverage rate: 20% by mass or more and 60% by mass or less>
The coverage is the mass of the coating material relative to the total mass of the covered electrode. When the coverage is 20% by mass or more, the shielding effect of the coating material can be sufficiently obtained, and good blow resistance can be obtained. Therefore, the coverage is preferably 20% by mass or more, and more preferably 25% by mass or more. On the other hand, if the coverage is 60% by mass or less, good hole properties can be obtained. In addition, since the metal components in the coating material can be sufficiently melted by the arc heat, it is possible to prevent unmelted metal particles from being mixed into the weld metal, and the unmelted metal particles can be easily removed. It is possible to prevent welding defects caused by metal particles. Therefore, the coverage is preferably 60 mass % or less, and more preferably 55 mass % or less.

Conventional covered metal arc welding rods absorb moisture when a day or so has passed since the rod was opened to use, and so the rod must be dried again, for example by placing it in a furnace. The covered metal arc welding rod according to the present embodiment, which has the above-mentioned configuration, has excellent resistance to moisture absorption, so it is possible to suppress the occurrence of blowholes during welding even several hours after opening without the need for drying again.

[Method of manufacturing a covered electrode]
The method for producing the covered metal arc welding rod according to the present embodiment is not particularly limited, but for example, the covered metal arc welding rod can be produced by the method described below.
One manufacturing method involves first preparing a core wire and preparing a coating material mixed with a binder such as water glass, applying the coating material around the core wire to the desired coating rate described above, and then firing the resulting material at a temperature of, for example, 100 to 550°C to remove moisture.

[Manufacture of covered metal arc welding rods (test materials)]
Hereinafter, examples of the invention in which the components contained in the covered electrode are within the content ranges specified in the present invention will be described in comparison with comparative examples in which the components are outside the ranges of the present invention.
First, a coating material was applied around a core wire made of a Ni-based alloy and then dried to produce a covered electrode as a test material with various amounts of contained components. The diameter of the core wire was 3.2 mm.

[Evaluation of Shielded Metal Arc Welding Electrodes]
The moisture content of the coating of the obtained covered electrode was measured by the Karl Fischer method (KF method). Specifically, the obtained covered electrode was pre-dried, and then the covered electrode was allowed to absorb moisture under the following moisture absorption conditions. After the moisture absorption, the coating was scraped off and the moisture content of only the coating was measured. The pre-drying conditions, moisture absorption conditions and moisture content measurement conditions are shown below.

Bar pre-drying temperature and time: 250°C, 1 hour Moisture absorption conditions (temperature x relative humidity) and time: 30°C x 80% Rh, 24 hours Measurement method: Karl Fischer method Extraction temperature: 750°C
Extraction atmosphere: dry air

In this example, coatings with a moisture content of 15,000 ppm or less were judged to have excellent moisture absorption resistance, and coatings with a moisture content of 10,000 ppm or less were judged to have particularly excellent moisture absorption resistance.

The coverage of the coating material for each of the invention examples and comparative examples, the contents of Li, Na and K in the coating material relative to the total mass of the coating material, and the ratio of the Li content to the K content ([Li]/[K]) are shown in Table 1 below, and the measurement results of the contents of components and the moisture content in the covered metal arc welding rod relative to the total mass of the covered metal arc welding rod are shown in Table 2 below.
In [Li]/[K], [Li] is the Li content in the coating agent expressed as mass % relative to the total mass of the coating agent, and [K] is the K content in the coating agent expressed as mass % relative to the total mass of the coating agent. In the columns for the content of each component shown in Tables 1 and 2, "-" indicates that Li was not added during the production of the coating agent.

As shown in Tables 1 and 2 above, in invention examples No. 1 to 7, the content of the components in the coating and the content of the components in the covered electrode were within the range of the present invention, so the moisture content after the 24-hour moisture absorption test was 15,000 ppm or less, and the moisture absorption resistance of the coating was excellent. In particular, in invention examples No. 1 to 6, the K content in the coating was within the preferred range of the present invention, so the moisture content after the 24-hour moisture absorption test was 10,000 ppm or less, and the moisture absorption resistance was even better. In addition, it was confirmed that when welding was performed using the wires of invention examples No. 1 to 7, which had a moisture content of 15,000 ppm or less, the occurrence of blowholes in the weld metal could be prevented. It was also confirmed that the strength and toughness of the weld metal was good for the invention examples.

On the other hand, in Comparative Examples 1, 6, 7, and 9, the Li content and [Li]/[K] value in the coating agent were below the lower limit of the range of the present invention, and in Comparative Examples 2 and 5, the Li content in the coating agent was below the lower limit of the range of the present invention, so the moisture content in the coating agent was high in all cases.

In addition, in Comparative Example No. 3, the K content in the coating exceeded the upper limit of the range of the present invention, and in Comparative Examples No. 4 and 8, the Li content and [Li]/[K] value in the coating were below the lower limit of the range of the present invention, and the K content exceeded the upper limit of the range of the present invention, so the moisture content in the coating was high in both cases.

As described above in detail, according to the present invention, by controlling the content of components in the coating and the content of components in the covered metal arc welding rod within a specific range, it is possible to obtain a Ni-based alloy covered metal arc welding rod that has excellent moisture absorption resistance of the coating and can suppress the occurrence of blowholes during welding.

Claims (5)

A Ni-based alloy covered metal arc welding rod in which a core wire is covered with a coating material,
With respect to the total mass of the Ni-based alloy covered metal arc welding rod,
_SiO2 : 1% by mass or more and 7% by mass or less,
_CO2 : 2.5% by mass or more and 7.0% by mass or less,
F: 0.5% by mass or more and 5.0% by mass or less; and Ni: 40% by mass or more,
Either or _both of _TiO2 and _Al2O3 ,
TiO ₂ : more than 0 mass % and not more than 2.0 mass %; and Al ₂ O ₃ : more than 0 mass % and not more than 2.0 mass %,
The coating agent contains, based on the total mass of the coating agent,
Li: 0.3% by mass or more and 1.2% by mass or less,
Na: 0.5% by mass or more and 1.5% by mass or less; and K: 0.6% by mass or more and 1.8% by mass or less;
When the Li content in the coating agent is expressed as [Li] in mass% relative to the total mass of the coating agent, and the K content in the coating agent is expressed as [K] in mass% relative to the total mass of the coating agent,
A Ni-based alloy covered metal arc welding rod, characterized in that [Li]/[K] is 0.15 or more and 1.4 or less. The Ni-based alloy covered metal arc welding rod according to claim 1, characterized in that the coating rate of the coating agent is 20% by mass or more and 60% by mass or less. Furthermore, with respect to the total mass of the Ni-based alloy covered metal arc welding rod,
The Ni-based alloy covered metal arc welding rod according to claim 1 or 2, characterized in that C is 1.0 mass % or less. Furthermore, with respect to the total mass of the Ni-based alloy covered metal arc welding rod,
Al: more than 0% by mass and not more than 2.0% by mass,
Ti: more than 0% by mass and not more than 2.0% by mass,
Mg: more than 0% by mass and not more than 0.5% by mass, and
The Ni-based alloy covered metal arc welding rod according to any one of claims 1 to 3, characterized in that it contains at least one selected from Fe: more than 0 mass% and 12.0 mass% or less. Furthermore, with respect to the total mass of the Ni-based alloy covered metal arc welding rod,
Cr: more than 0% by mass and not more than 20.0% by mass,
Mo: more than 0% by mass and not more than 15.0% by mass,
W: more than 0% by mass and not more than 5.0% by mass,
Mn: more than 0% by mass and not more than 5.0% by mass, and
The Ni-based alloy covered metal arc welding rod according to any one of claims 1 to 4, characterized in that it contains at least one selected from Nb: more than 0 mass% and 5.0 mass% or less.