JPH04351290A - Coated electrode of 'hastelloy(r)' system for steel for cryogenic service having excellent ductility and fracture resistance characteristic - Google Patents

Abstract

PURPOSE:To assure the high tensile strength, high toughness and high-temp. crack resistance of a weld metal by limiting the impurities and gaseous components of a core wire and limiting the ratio of the metal carbonate and metal fluoride of a coating material and the contents of SiO2 and total moisture. CONSTITUTION:The coated electrode of a 'Hastelloy(R)' system for steels for cryogenic service is formed by incorporating 65 to 85% Ni, 15 to 24% Mo and 2.0 to 4.0% W into the core wire of this coated electrode and limiting the components to <=0.16% Si, <=0.008% oxygen, <=0.010% nitrogen, <=0.0007% hydrogen, <=0.010% P, <=0.010% S, and 0.015% P+S. Fe is limited to <=5%, Cr to <=2.0%, Cr to <=1.0% and Mn to <=2.0%. The metal carbonate is incorporated at 50 to 70% and the metal fluoride at 10 to 25% of the total weight of the coating material into the coating material. The metal carbonate and metal fluoride are so compounded as to attain 3.05 to 4.10 ratio thereof. Degassing agents, such as Al, Ti, Si, and Mg are compounded at 5.0 to 10.0% and the SiO2 is limited to <=4.0. The total moisture content is limited to <=0.20%.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to cryogenic steel.5.
Ni-Mo used for welding 5% Ni steel and 9% Ni steel
The present invention relates to a coated arc welding rod based on a so-called hastelloy base alloy, and in particular to a coated arc welding rod based on a hastelloy, which has excellent ductile fracture resistance properties of weld metal at extremely low temperatures.

0002

[Prior Art] Hastelloy-based coated arc welding rods for cryogenic steel have already been commercially available, and as disclosed in JP-A-59-107789 and JP-A-62-197297, welding can be performed in all positions. The hastelloy coated arc welding rod is a 9% Ni steel L, which has good properties and is a weld metal with an austenitic structure that has high strength, high toughness, and excellent hot cracking resistance.
It is put into practical use for welding NG (liquefied natural gas) tanks.

[0003] However, due to Japan's energy situation and pollution problems, the demand for LNG continues to increase, and LNG storage tanks have recently become larger. L
As the size of the NG tank increases, the maximum plate thickness (lowermost layer) of 9% Ni steel inevitably becomes extremely thick at 40 to 50 mm, which is unprecedented. Complex and severe forces are applied to the welds at the bottom of such extremely thick 9% Ni steel LNG tanks.
During a water filling test in which the weld is filled with water, which has a specific gravity approximately twice that of G, to check for leaks, the force applied to the weld is extremely severe. Therefore, in order to avoid large-scale destruction of the LNG tank, it is first necessary to prevent not only the occurrence of cracks based on welding defects, but also the propagation of ductile cracks during this water filling test. The second is -163℃ during LNG storage.
In order to prevent large-scale fractures, it is important to be able to prevent not only the occurrence of cracks but also the subsequent propagation of ductile cracks even at extremely low temperatures. Under such extremely harsh environments, even the austenitic weld metal produced by the conventional coated arc welding rod, which has relatively excellent properties as described above, has poor resistance to ductile crack propagation, that is, ductile fracture resistance. In recent years, it has become clear that the construction of completely safe large LNG tanks is not always sufficient and that it is difficult to construct completely safe large LNG tanks. A coated arc welding rod that can be secured is strongly desired.

0004

[Problems to be Solved by the Invention] The object of the present invention is to
-Using Mo-based alloy core wire, it goes without saying that welding workability in all positions is good, and even in extremely low temperatures and harsh environments, cracks do not only occur, but also propagate ductile cracks and cause large scale damage. It is an object of the present invention to provide a welding rod that can secure weld metal with excellent ductile fracture resistance characteristics that can prevent fracture.

[0005]

[Means for Solving the Problem] The gist of the present invention is that 65-85% Ni, 15-24% Mo, 2.0
Contains ~4.0% W and the amount of Si in the core is 0.1
6% or less, oxygen content 0.008% or less, nitrogen content 0.0
10% or less, hydrogen amount 0.0007% or less, P amount 0.
0.010% or less, S amount 0.010% or less, P+S 0.010% or less.
At the same time, the amount of Fe in one or both of the core wire or coating material is limited to 5% or less, the Cr amount is 2.0% or less, the Cu amount is 1.0% or less, and the M
The amount of n is regulated to 2.0% or less, and 50% of the total weight of the coating material is
~70% metal carbonate and 10~25% metal fluoride are blended so that the ratio of metal carbonate/metal fluoride is 3.05~4.10, and Al1. 5-4
．． 0%, Ti2.5-5.0%, Si0.1-1.5%
, a degassing agent is blended so that the total of two or three or more types of Mg0.05 to 1.5% is 5.0 to 10.0%,
Furthermore, the core wire is coated with a coating material in which the silicate compound is regulated to 4.0% or less in terms of SiO2, and the total water content in the coating material is limited to 0.20% or less. Hastelloy coated arc welding rod for cryogenic steel with excellent ductile fracture resistance.

[0006] In this specification, % refers to % by weight, and the total weight of the coating material does not include solid components such as SiO2 and K2 O contained in the water glass used for coating the coating material. The present invention will be explained in detail below along with its operation.

[0007]

[Function] The present inventors have discovered a coating for cryogenic steel that can ensure weld metal with excellent ductile fracture resistance properties that can prevent the propagation of ductile cracks even after cracks have occurred at extremely low temperatures and in harsh environments. We conducted extensive research with the aim of developing arc welding rods. As a result, the Si, P, and S impurities and the oxygen, nitrogen, and hydrogen gas components of the so-called Hastelloy core wire of Ni-Mo-W are limited to trace amounts, and the auxiliary additives of Fe, Cr, Cu, and Mn are Specify the metal carbonate and metal fluoride in the coating material, limit the metal carbonate/metal fluoride ratio, and degas with two or more of Al, Ti, Si, and Mg. , and limiting SiO2 and total water content, it is possible to significantly improve the ductile fracture resistance of weld metal without impairing welding workability, without causing welding defects such as blowholes and cracks, etc. I gained new knowledge that it is possible.

Next, each component of the core wire of the present invention will be explained. Ni is a weld metal with an austenitic structure that is stable even at extremely low temperatures, and has excellent tensile properties, ductility, and
Necessary to ensure toughness, etc. Mo is necessary in coexistence with Ni to ensure that the weld metal has high tensile strength, high toughness, and excellent hot cracking resistance over a wide temperature range from high temperatures to extremely low temperatures.

[0009] W is necessary in coexistence with Ni and Mo to ensure high tensile strength of the weld metal over a wide temperature range from high temperatures to extremely low temperatures. Si in the core wire increases the amount of Si in the weld metal, which causes deterioration of the ductility, impact toughness, and ductile fracture resistance properties of the weld metal especially at extremely low temperatures, and also promotes the occurrence of hot cracking in the weld metal. Therefore, it must be controlled low. Controlling the amount of Si in the core wire to a low level means that Al, Ti, Si, Mg
In combination with adding two or more types of degassing agents, specifying the metal carbonate/metal fluoride in the coating material within a specific range, and lowering the SiO2 content in the coating material, This is one of the main structural requirements for ensuring a weld metal that has excellent ductility, impact toughness, and ductile fracture resistance even at extremely low temperatures without impairing welding workability and weld defect resistance.

[0010] Gaseous components such as oxygen, nitrogen, and hydrogen cause deterioration of the ductility, impact toughness, and ductile fracture resistance characteristics of weld metal at extremely low temperatures, and also promote the occurrence of hot cracking in weld metal, so they must be controlled to a low level. . In particular, when the amount of oxygen in the core wire is large, the tendency for the amount of oxygen in the weld metal to increase is promoted, and the deterioration of the properties of the weld metal becomes significant. The so-called impurity elements P and S cause deterioration of the ductility, impact toughness, and ductile fracture resistance characteristics of the weld metal at extremely low temperatures, and also promote the occurrence of hot cracking in the weld metal, so they must be controlled to a low level.

[0011] Here, the reason for controlling the gas components of Si, oxygen, nitrogen, and hydrogen, and the impurity elements of P and S in the core wire will be explained. As mentioned above, these components deteriorate the ductile fracture resistance properties of the weld metal, especially at extremely low temperatures, so their content in the weld metal must be kept as low as possible. The composition and cleanliness of the weld metal can be controlled to some extent by the coating material, and it goes without saying that the composition of the coating material is specified as described below in order to achieve appropriate composition and cleanliness. However, most of the gas components of Si, oxygen, nitrogen, hydrogen, and impurity elements P and S in the core wire migrate into the weld metal, which affects the ductile fracture resistance of the weld metal, especially at extremely low temperatures. In order to keep the content of these components in the weld metal low enough to improve the The content of impurity elements must be controlled as low as possible.

[0012] Fe, Cr, Cu, and Mn are used to improve hot forgeability, rollability, and wire drawability during the production of wire rods, to improve the tensile strength and corrosion resistance of weld metal, and to further improve weld metal. These auxiliary additives are added for the purpose of creating a stable austenitic structure, etc., but these auxiliary additives deteriorate the ductility, impact toughness, and ductile fracture resistance of the weld metal at extremely low temperatures. It must be regulated because it tends to encourage cracking.

[0013] Here, auxiliary additives such as Fe, Cr, Cu, and Mn are added to the coating material for the purpose of improving the tensile strength and corrosion resistance of the weld metal, and making the weld metal an even more stable austenitic structure. However, in this case, the amount added should be kept low so as not to impair the ductile fracture resistance properties of the weld metal at extremely low temperatures.

Further, each component of the coating material of the present invention will be explained. Metal carbonates decompose and produce CO and CO2 gas during welding, shielding the molten pool from the atmosphere, and releasing nitrogen,
It is effective in preventing the deterioration of weld metal properties and the generation of blowholes due to the contamination of oxygen and hydrogen. Furthermore, it is possible to impart appropriate viscosity and fluidity to the molten slag, and to obtain a smooth and sound weld bead in all positions. In addition, metal carbonates keep the atmosphere during welding highly basic, and reduce Si and P in the weld metal.
It reduces the impurity component of S and improves the hot cracking resistance of the weld metal, as well as the ductility, impact toughness, and ductile fracture resistance characteristics at extremely low temperatures.

The metal fluoride imparts appropriate viscosity and fluidity to the molten slag, and is effective in obtaining a smooth and sound weld bead in all positions. In addition, by keeping the atmosphere highly basic during welding and reducing the impurity components of Si, P, and S in the weld metal, it improves the hot cracking resistance of the weld metal and the ductility at extremely low temperatures.
It is effective in improving impact toughness and ductile fracture resistance.

[0016] Here, regulating the metal carbonate/metal fluoride ratio within a specific range means controlling the amount of Si in the core wire to a low level, and controlling the amount of Al, Ti, Si, and Mg in the coating material. By adding two or more types of degassing agents and by controlling the SiO2 content in the coating material, it is possible to achieve excellent ductility even at extremely low temperatures without impairing welding workability and weld defect resistance. Impact toughness and ductile fracture resistance properties are one of the main constituents to ensure weld metals have properties.

[0017] Degassing agents such as Al, Ti, Si, and Mg reduce the amount of nitrogen, oxygen, and hydrogen in the weld metal by reacting with gas components during welding, thereby preventing the occurrence of blowholes in the weld metal and at the same time improving the welding process. Ductility and impact toughness of metals at extremely low temperatures,
Necessary to improve ductile fracture resistance properties. especially,
Adding two or more of these degassing agents activates the degassing reaction and significantly improves the properties of the weld metal. Adding a specific amount of two or more types of degassing agents Al, Ti, Si, and Mg to the coating material can reduce Si in the core wire.
Limiting the amount of SiO
The main structural requirements for ensuring a weld metal that has excellent ductility, impact toughness, and ductile fracture resistance even at extremely low temperatures without impairing welding workability and weld defect resistance, coupled with a low regulation of 2 minutes. one of.

[0018] Due to reactions such as decomposition during welding, silicate compounds mainly consisting of SiO2 tend to make the atmosphere during welding acidic and increase the amount of oxygen in the weld metal. In order to increase the amount of oxygen and Si in the weld metal, it causes deterioration of the ductility, impact toughness and ductile fracture resistance properties of the weld metal, especially at extremely low temperatures, and also promotes the tendency of hot cracking in the weld metal, so it is limited to a low level. Must. Si in coating material
Restricting the O2 content to a low level means restricting the amount of Si in the core wire to a low level, and increasing the amount of Al, Ti, Si, and Mg into the coating material.
By adding a degassing agent or three or more types of degassing agents, and by regulating the metal carbonate/metal fluoride ratio in the coating material within a specific range, welding workability and weld defect resistance are not impaired. This is one of the main structural requirements to ensure a weld metal with excellent ductility, impact toughness and ductile fracture resistance properties even at extremely low temperatures.

Moisture in the coating material increases the amount of hydrogen and oxygen in the weld metal due to reactions such as decomposition during welding, which affects the ductility of the weld metal from high temperatures to extremely low temperatures, the impact toughness of the weld metal at extremely low temperatures, and It is necessary to limit it to a low level because it causes deterioration of ductile fracture resistance characteristics and also causes welding defects such as blowholes and hot cracks. The reasons for limiting the ingredients in the present invention will be described below.

[0020]Ni in the core wire is a basic component for creating a weld metal with an austenitic structure that is stable even at extremely low temperatures and ensuring excellent tensile properties, ductility, toughness, etc. at extremely low temperatures, and is required to be at least 65%. It is. 9% Ni if over 85%
The tensile strength required for cryogenic steel such as steel is insufficient. Therefore, the amount of Ni in the core wire is set to 65 to 85%. The Mo content in the core wire is 15% to ensure that the weld metal, in coexistence with Ni, has high tensile strength, high toughness, and excellent hot cracking resistance in a wide temperature range from high temperatures to extremely low temperatures. The above is necessary. If it exceeds 24%, the impact toughness and ductility of the weld metal at extremely low temperatures will deteriorate significantly. Therefore, the amount of Mo in the core is 1
5 to 24%.

[0021] W in the core wire is required to be 2.0% or more in order to ensure high tensile strength of the weld metal in a wide temperature range from high temperatures to extremely low temperatures in coexistence with Ni and Mo. . If it exceeds 4.0%, the impact toughness and ductility of the weld metal at extremely low temperatures will deteriorate significantly. Therefore, the amount of W in the core is 2.0 to 4
．． Set to 0%. When the amount of Si in the core wire exceeds 0.16%, the ductility, impact toughness, and ductile fracture resistance characteristics of the weld metal, especially at extremely low temperatures, are significantly deteriorated. Therefore, the amount of Si in the core wire is limited to 0.16% or less.

[0022] When oxygen in the core wire exceeds 0.008%, it increases the amount of oxygen in the weld metal and significantly impairs the ductility of the weld metal from high temperatures to extremely low temperatures, impact toughness at extremely low temperatures, and ductile fracture resistance. This causes deterioration and increases the tendency for hot cracking to occur in the weld metal. Therefore, the amount of oxygen in the core is 0.
Limit to 0.008% or less. Nitrogen in the core wire is 0.010
If it exceeds %, the ductility, impact toughness and ductile fracture resistance properties of the weld metal at extremely low temperatures will be significantly deteriorated, and it will also cause blowholes to occur during welding. Therefore, the amount of nitrogen in the core wire is limited to 0.010% or less.

[0023] When hydrogen in the core wire exceeds 0.0007%, it significantly deteriorates the ductility, impact toughness and ductile fracture resistance characteristics of the weld metal at cryogenic temperatures, and also causes blowholes to occur during welding. Therefore, the amount of hydrogen in the core is 0.0
Limit to 0.007% or less. P in the core is 0.010%
When the ductility of the weld metal from high temperature to cryogenic temperature exceeds
It significantly deteriorates the ductile fracture resistance of weld metal at extremely low temperatures and also deteriorates the hot cracking resistance of weld metal. Therefore, the amount of P in the core is limited to 0.010% or less.

[0024] When the S content in the core wire exceeds 0.010%,
It significantly deteriorates the ductility of the weld metal from high temperatures to extremely low temperatures, the ductile fracture resistance characteristics of the weld metal at extremely low temperatures, and also deteriorates the hot cracking resistance of the weld metal. Therefore, the amount of S in the core wire is limited to 0.010% or less. In addition, P in the core wire
If the total amount of S and S exceeds 0.015%, the ductility of the weld metal from high temperatures to extremely low temperatures, the ductile fracture resistance characteristics of the weld metal at extremely low temperatures, and the hot cracking resistance of the weld metal will deteriorate. . Therefore, the amount of S+P in the core wire is limited to 0.015% or less.

[0025] Fe can be added as an auxiliary for the purpose of improving hot forgeability, rolling/drawability during wire production, or improving the conformability of weld metal, but it is If the amount of Fe in one or both of them exceeds 5% by weight of the core, the impact toughness and ductile fracture resistance of the weld metal at extremely low temperatures will be significantly degraded. Therefore, the amount of Fe in one or both of the core wire and the coating material is regulated to 5% or less in terms of core wire weight ratio.

[0026] Cr can be added as an auxiliary for the purpose of improving the tensile strength and corrosion resistance of the weld metal, but if the amount of Cr in one or both of the core wire and the coating material is 2.5% by weight ratio of the core wire.
If it exceeds 0%, the impact toughness and ductile fracture resistance characteristics of the weld metal at extremely low temperatures will be significantly deteriorated. Therefore, the amount of Cr in one or both of the core wire and coating material is 2.0 in terms of core wire weight ratio.
% or less.

[0027]Cu is added as an auxiliary for the purpose of improving hot forgeability, rolling/drawability during wire rod production, improving the tensile strength and corrosion resistance of the weld metal, or stabilizing the austenite structure of the weld metal. However, if the amount of Cu in one or both of the core wire and the coating material exceeds 1.0% by weight of the core wire, the impact toughness and ductile fracture resistance characteristics of the weld metal at cryogenic temperatures are significantly deteriorated. Therefore, the amount of Cu in one or both of the core wire and the coating material is regulated to 1.0% or less in terms of core wire weight ratio.

Mn can be added as an auxiliary for the purpose of stabilizing the austenite structure of the weld metal and deoxidizing and desulfurizing during welding, but the amount of Mn in either or both of the core wire and the coating material depends on the core wire weight. When the ratio exceeds 2.0%, the impact toughness and ductile fracture resistance characteristics of the weld metal at cryogenic temperatures are significantly deteriorated. Therefore, the amount of Mn in one or both of the core wire and the coating material is regulated to 2.0% or less in terms of core dose ratio.

However, the following equation is used to convert the ratio of the alloy components to the total weight of the coating material (coating material weight ratio) to the core weight ratio. Cord weight ratio (%) = Coating material weight ratio (%) x Coverage rate (%) / (100 - Coverage rate (%)) In addition to these auxiliary additives, Al, Ti, Mg, etc. are refined. 0.1% Al each for the purpose of improving degassing and hot forging properties.
Hereinafter, even if Ti is contained in the core wire in a range of 0.2% or less and Mg 0.02% or less, the effects of the present invention will not be impaired.

The metal carbonate in the coating material decomposes CO and CO2 gas during welding, shields the molten pool from the atmosphere, and prevents deterioration of properties of the weld metal and generation of blowholes due to contamination with nitrogen, oxygen, and hydrogen. It also gives appropriate viscosity and fluidity to the molten slag, forms a smooth and healthy weld bead in all positions, and keeps the atmosphere during welding highly basic to eliminate Si, P, and S in the weld metal. In order to improve the hot cracking resistance of the weld metal and the ductility, impact toughness, and ductile fracture resistance characteristics of the weld metal at extremely low temperatures by reducing the impurity components, it is necessary to use 50% or more of the total weight of the coating material. However, 70%
If it exceeds this, welding workability deteriorates, such as deterioration of slag removability, increase in spatter, and deterioration of bead shape. Therefore, the amount of metal carbonate should be 50 to 70% based on the total weight of the coating material.

[0031] The metal carbonate mentioned here refers to, for example, lime carbonate, barium carbonate, magnesium carbonate, lithium carbonate, strontium carbonate, manganese carbonate, or composite additives thereof. The metal fluoride in the coating material gives appropriate viscosity and fluidity to the molten slag, forming a smooth and sound weld bead in all positions, and also keeps the atmosphere during welding highly basic so that the weld metal does not melt. In order to reduce the impurity components of Si, P, and S in order to improve the hot cracking resistance of the weld metal and the ductility, impact toughness, and ductile fracture resistance characteristics at extremely low temperatures,
10% or more is required. However, if it exceeds 25%, welding workability deteriorates, such as deterioration in slag removability, increase in spatter, and deterioration in bead shape. Therefore, the amount of metal fluoride is 10 to 25% based on the total weight of the coating material.

[0032] The metal fluorides mentioned here include, for example, fluorite, cryolite, aluminum fluoride, magnesium fluoride,
Refers to barium fluoride, lithium fluoride, sodium fluoride, potassium fluoride, or composite additives thereof. The metal carbonate/metal fluoride ratio is determined by limiting the amount of Si in the core wire to a low level, by adding two or more degassing agents of Al, Ti, Si, and Mg to the coating material; Coupled with controlling the SiO2 content in the coating material to a low level, the weld metal has excellent ductility, impact toughness, and ductile fracture resistance even at extremely low temperatures without impairing welding workability in all positions and weld defect resistance. It must be in the range of 3.05 to 4.10 to ensure that. If this ratio is less than 3.05, welding workability in all positions and weld defect resistance will deteriorate, and if it exceeds 4.10, the ductility, impact toughness, and ductile fracture resistance characteristics of the weld metal will deteriorate, especially at extremely low temperatures. do.

[0033] The Al, Ti, Si, and Mg degassing agents in the coating material reduce the amount of nitrogen, oxygen, and hydrogen in the weld metal by reacting with gas components during welding, and prevent the generation of blowholes in the weld metal. It is necessary to prevent this and at the same time improve the ductility, impact toughness, and ductile fracture resistance properties of the weld metal at cryogenic temperatures. In particular, adding two or more of these degassing agents activates the degassing reaction and significantly improves the properties of the weld metal. Due to the synergistic effect of limiting the amount of Si in the core wire to a low level, regulating the ratio of metal carbonate/metal fluoride in the coating material to a specific range, and regulating the SiO2 content in the coating material to a low level, In order to ensure a weld metal that has excellent ductility, impact toughness, and ductile fracture resistance even at extremely low temperatures without impairing welding workability and weld defect resistance,
Two or more of Al, Ti, Si, and Mg are added to the coating material.

[0034] Al has no effect if it is less than 1.5% in terms of a single metal, and if it exceeds 4.0%, it conversely deteriorates the ductility, impact toughness, and ductile fracture resistance characteristics of the weld metal at extremely low temperatures. Ti has no effect if it is less than 2.5% in terms of the elemental metal, and if it exceeds 5.0%, it conversely deteriorates the ductility, impact toughness, and ductile fracture resistance characteristics of the weld metal at extremely low temperatures. Si has no effect if it is less than 0.1% in terms of a single metal, and if it exceeds 1.5%, it will conversely deteriorate the ductility, impact toughness, and ductile fracture resistance characteristics of the weld metal at extremely low temperatures. Mg has no effect if it is less than 0.05% in terms of elemental metal, and 1
．． Conversely, if it exceeds 5%, the ductility of the weld metal at extremely low temperatures decreases.
Deteriorates impact toughness and ductile fracture resistance properties. Therefore, in terms of the total weight of the coating material, Al
1.5-4.0%, Ti2.5-5.0%, Si0.1
~1.5%, Mg0.05~1.5%. In addition, if the total of two or more of these degassing elements is less than 5.0% in terms of single metal, there is no effect, and 10.0%
On the other hand, exceeding this value will deteriorate the ductility, impact toughness, and ductile fracture resistance properties of the weld metal at extremely low temperatures. Therefore, the total of two or more of these degassing elements in terms of single metal is 5
．． 0 to 10.0%.

If the silicate compound in the coating material exceeds 4.0% in terms of SiO2, a reaction occurs during welding, making the welding atmosphere more acidic and reducing oxygen and Si in the weld metal.
This increases the amount of carbon dioxide and deteriorates the ductility, impact toughness and ductile fracture resistance properties of the weld metal, especially at cryogenic temperatures, and also increases the tendency of hot cracking in the weld metal. Therefore, the silicate compound in the coating material is restricted to 4.0% or less in terms of SiO2 based on the total weight of the coating material. Regulating the silicate compound in the coating material to 4.0% or less in terms of SiO2;
Limiting the amount of Si in the core wire to a low level, Al in the coating material,
The synergistic effect of adding two or more types of degassing agents such as Ti, Si, and Mg and regulating the ratio of metal carbonate/metal fluoride in the coating material to a specific range makes welding work easier. It is possible to secure a weld metal that has excellent ductility, impact toughness, and ductile fracture resistance even at extremely low temperatures without impairing properties, weld defect resistance, and hot cracking resistance.

The silicate compound referred to herein refers to, for example, silica sand, wollastonite, potassium feldspar, mica, talc, potassium silicate, sodium silicate, or composite additives thereof. If the total water content in the coating material exceeds 0.20%, reactions such as decomposition during welding will increase the amount of hydrogen and oxygen in the weld metal, reducing the ductility of the weld metal from high temperatures to extremely low temperatures. It deteriorates the impact toughness and ductile fracture resistance properties of weld metal, and causes weld defects such as blowholes and hot cracks. Therefore, the total water content in the coating is 0 relative to the total weight of the coating.
．． Limit to 20% or less.

In addition to the above components, the coating material contains, for example, Ni
, Mo, W, etc. can be appropriately blended to compensate for oxidative consumption during welding or to obtain necessary alloy components. However, when Ni, Mo, W, Cr, Cu, Mn, etc. are mixed and added in the form of ferroalloy, the sum of the value obtained by converting their Fe content to the weight ratio of the core wire and the amount of Fe in the core wire is 5.
Must be less than %.

[0038] Furthermore, titanium oxide, aluminum oxide, magnesium oxide, potassium oxide, sodium oxide, or a composite additive thereof may be suitably added to the coating material within a range of 3% or less. Even if they are added, the effects of the present invention are not impaired. As described above, according to the present invention, the impurities of Si, P, and S and the gas components of oxygen, nitrogen, and hydrogen are limited to trace amounts, and
In the so-called hastelloy core wire of Ni-Mo-W with regulated auxiliary additives, metal carbonate and metal fluoride are specified, the metal carbonate/metal fluoride ratio is limited, and Al, Ti, By adding a specific amount of two or more degassing elements, Si and Mg, and controlling the amount of SiO2 and total moisture to a very small amount, blowholes can be removed for the first time without impairing welding workability. , a weld metal with excellent ductile fracture resistance properties that does not cause welding defects such as cracks, does not easily generate cracks under extremely low temperatures and harsh environments, and can prevent the propagation of ductile cracks even after cracks have occurred can be obtained. .

Referring to an example of the method for manufacturing the welding rod of the present invention, a Ni-Mo-W base line and coating powder are prepared, and the coating powder and water glass (potassium silicate aqueous solution, sodium silicate aqueous solution, etc.) are mixed. After mixing and coating the core wire, approximately 400
Dry at ℃ for about 1 hour. The outer diameter of the coating is D/d (D
; coated outer diameter, d; core wire diameter) is preferably 1.3 to 1.8, and the coverage is preferably 20 to 40%.

[0040] The effects of the present invention will be specifically explained below with reference to Examples.

[0041]

[Example] Tables 1 and 2 show the chemical components of the sample cores. The dimensions of the core wire are 4.0 mm in diameter and 350 m in length.
It was set as m. In addition, symbol D in the table indicates that the amount of Si exceeds 0.16%, symbol E indicates that the amount of oxygen exceeds 0.008% and at the same time the amount of P+S exceeds 0.015%, and symbol F indicates that the amount of Ni exceeds 6%.
When the amount of Mo is less than 5%, the amount of Mo exceeds 24%, and the amounts of Cr, Cu, and Mn exceed 2.0%, 1.0%, and 2.0%, respectively, and are core wires outside the present invention.

Tables 3 to 6 show the compositions of welding rods made from these combinations of core wires and coating materials. The outer diameter of the coating was set to 6.4 mm (
D/d=1.6), and the coverage was about 30%. As the water glass, an aqueous solution of potassium silicate and sodium silicate with a solid mass of 8% was used. Tables 7 and 8 show that the current of 14
The chemical composition of the weld metal of these welding rods welded at 0A (AC) is shown.

[0043] Tables 9 to 11 show JIS Z 3225
The mechanical properties of the weld metal of these welding rods welded at a current of 140 A (AC) according to the specified method, the welding workability test results, X-ray performance test results, hot cracking test results, and ductile fracture resistance of these welding rods. Characteristic test results are shown. In addition, the welding workability test and the X-ray performance test were performed using a plate thickness of 12.7 mm,
60°Y with width 400mm and length 500mm (= welding length)
Using 9% Ni steel with a mold groove, the vertical position has a current of 11
0~130A (AC), welding speed 40~120mm/m
in, horizontal position: current 120-140A (AC), welding speed 140-300mm/min, upward position: current 110-130A (AC), welding speed 40-150mm
/min in each position and under each welding condition.

[0044] Hot cracking test is JIS Z 3155
Using the "C type jig restraint butt weld cracking test method", 9% Ni steel with a plate thickness of 25.4 mm was used, a 50° Y type groove, root face t/2 (=12.7 mm), root gap 2 mm, and electric current. 140A (AC), welding speed 250
The test was carried out under the test conditions of mm/min. The ductile fracture resistance characteristic test was conducted using a plate with a thickness of 40 mm, a width of 750 mm, and a length of 750 mm.
mm (= welding length), front side 50° depth 25mm, back side 7
Using 9% Ni steel with an X groove of 0° depth 12 mm, root face 3 mm, and root gap 2 mm, a current of 1
20-130A (AC), welding speed 40-70mm/m
After welding the joint in a vertical position under the welding conditions of 40 mm with a 48 mm side notch in the center of the weld metal.
t (=plate thickness) x 160mm (=welding direction) x 750m
A test piece of m (width) was processed and collected, and -
CTO of BS5762-79 in liquid nitrogen at 196°C
Perform 3-point bending according to the D test and ASTM E813
ANNEX (Al.SPECIAL REQUIRE
MENTS FOR TESTING BEND SA
C due to the Unloading Compliance Act based on MPLES)
The TOD value and ductile fracture resistance value were determined. However, here,
The opening displacement amount at the maximum load was defined as the CTOD value, and the maximum value of the CTOD value was defined as the ductile fracture resistance value.

From the above, welding rod symbols 1, 2, 3,
6, 7, 8, 9, 10, 13, 14, 17, 18, 21
It is clear that No. 22 and No. 22 have excellent mechanical properties of the deposited metal, welding workability in all positions, X-ray performance, cracking resistance, and ductile fracture resistance characteristics of the joint weld metal at extremely low temperatures. On the other hand, looking at the comparative examples, welding rod number 4 has a ratio of metal carbonate/metal fluoride in the coating material of 4.10.
, the welding workability in all positions is poor, and as a result, the X-ray performance is poor, and furthermore, the ductile fracture resistance of the weld metal at extremely low temperatures is not particularly excellent.

Welding rod No. 5 has a metal carbonate/metal fluoride ratio in the coating material of less than 3.05, resulting in poor welding workability in all positions, resulting in poor X-ray performance, and further welding The metal's cryogenic ductile fracture resistance properties are also not particularly good. Welding rod symbol 11 is A in the coating material.
The total amount of degassing agents of Ti, Si, and Mg is less than 5.0%, which results in poor X-ray performance and a high amount of oxygen in the weld metal, resulting in poor tensile properties, hot cracking resistance, and ductility at cryogenic temperatures. Breakage resistance characteristics have deteriorated.

[0047] Welding rod symbol 12 indicates Al, Ti,
The total amount of Si and Mg degassing agents exceeds 10.0%, the amount of Si, Al, and Ti in the weld metal is large, and the tensile properties, hot cracking resistance, impact toughness at cryogenic temperatures, and ductile fracture resistance properties are improved. It has deteriorated. Welding rod symbol 15 is SiO in the coating material
2 amount exceeds 4.0%, the amount of Si and oxygen in the weld metal is large, and the tensile properties, hot cracking resistance, impact toughness at extremely low temperatures, and ductile fracture resistance characteristics are deteriorated.

[0048] Welding rod symbol 16 has a total moisture content of 0 in the coating material.
．． exceeding 20%, the amount of hydrogen and oxygen in the weld metal is large,
Tensile properties, hot cracking resistance, and ductile fracture resistance at extremely low temperatures are deteriorated. Welding rod code 19 has a metal carbonate/metal fluoride ratio in the coating material of less than 3.05, resulting in poor welding workability in all positions, resulting in poor X-ray performance, and The ductile fracture resistance properties at low temperatures are also degraded.

Welding rod code 20 has a SiO2 content in the coating material exceeding 4.0%, a large amount of Si and oxygen in the weld metal, and has good tensile properties, hot cracking resistance, impact toughness at extremely low temperatures, and ductile fracture resistance. Characteristics have deteriorated. Welding rod code 23 has a total of Al, Ti, Si, and Mg degassing agents in the coating material exceeding 10.0%, a large amount of Si, Al, and Ti in the weld metal, and has good tensile properties and high temperature cracking resistance. impact toughness and ductile fracture resistance properties at cryogenic temperatures.

[0050] Welding rod symbol 24 uses a core wire other than the present invention with a Si content exceeding 0.16%, so the Si content in the weld metal increases, resulting in poor tensile properties, hot cracking resistance, and impact at cryogenic temperatures. Toughness and ductile fracture resistance properties are degraded. Welding rod code 25 used a core wire outside the present invention with an oxygen content exceeding 0.008% and a total P and S content exceeding 0.015%, so oxygen and P and S in the weld metal were used. The tensile properties, hot cracking resistance, impact toughness at cryogenic temperatures, and ductile fracture resistance properties are deteriorated.

Welding rod symbol 26 has a Ni content of less than 65%, M
Since a core wire other than the present invention was used in which the o content exceeded 24% and the amounts of Cr, Cu, and Mn exceeded 2.0%, 1.0%, and 2.0%, respectively, the balance of the weld metal composition was collapsed,
Tensile properties, hot cracking resistance, impact toughness at cryogenic temperatures, and ductile fracture resistance properties are deteriorated.

[0052]

[Table 1]

[0053]

[Table 2]

[0054]

[Table 3]

[0055]

[Table 4]

[0056]

[Table 5]

[0057]

[Table 6]

[0058]

[Table 7]

[0059]

[Table 8]

[0060]

[Table 9]

[0061]

[Table 10]

[0062]

[Table 11]

[0063]

[Effects of the Invention] As explained above, the hastelloy-based coated arc welding rod for cryogenic steel of the present invention has good welding workability and X-ray performance in all positions, and also has good cracking resistance of the weld metal. Furthermore, because the weld metal has excellent ductile fracture resistance properties at extremely low temperatures, there are no welding defects such as blowholes and cracks, and cracks are difficult to occur under extremely low temperatures and harsh environments, and even after cracks occur, the weld metal remains ductile. This makes it possible to easily obtain a weld metal with excellent ductile fracture resistance that can prevent crack propagation. This means that it is possible to construct a completely safe large LNG tank in which a large-scale destruction accident is impossible, and it has great industrial effects and high utility value.

Claims (1)

[Claims] Claim 1: The core contains 65-85% Ni, 15
Contains ~24% Mo, 2.0~4.0% W, and the amount of Si in the core wire is 0.16% or less and the amount of oxygen is 0.008%.
% or less, nitrogen amount 0.010% or less, hydrogen amount 0.00% or less
07% or less, P amount 0.010% or less, S amount 0.01
0% or less, P+S is limited to 0.015% or less, and at the same time, the amount of Fe in one or both of the core wire or coating material is limited to 5% or less, the amount of Cr is 2.0% or less, and the amount of Cr is limited to 2.0% or less.
Regulating the u content to 1.0% or less and the Mn content to 2.0% or less,
50-70% metal carbonate and 10-70% based on the total weight of the coating material.
25% metal fluoride with a metal carbonate/metal fluoride ratio of 3
．． 05 to 4.10, and in terms of elemental metal, Al1.5 to 4.0% and Ti2.5 to 5.0%.
, Si0.1-1.5%, Mg0.05-1.5%2
A degassing agent is blended so that the total amount of one species or three or more species is 5.0 to 10.0%, and a silicate compound is added to SiO2.
ductile fracture resistance characterized by coating the core wire with a coating material that limits the total water content in the coating material to 0.20% or less, in terms of 4.0% or less. Excellent Hastelloy coated arc welding rod for cryogenic steel.