JP2016093823A - Solid wire for welding, welding method and weld metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid wire for welding capable of stably forming a weld metal representing stable favorable ultracold toughness without variation when welding 9%-Ni steels being a base material to each other.SOLUTION: A solid wire for welding contains, by mass%, more than 0-0.10% of C, more than 0-0.15% of Si, 0.1-0.80% of Mn, 8-15% of Ni, 0.015-0.050% of Ti, more than 0-0.005% of REM, more than 0-0.0065% of O and the balance Fe with inevitable impurities, and satisfies the following expression (1): 10≤18×[Mn]+71×[REM]+206×[Ti]≤20 ... (1) (in the expression, [ ] represents the content of each element in mass%).SELECTED DRAWING: None

Description

  The present invention relates to a welding solid wire suitable for welding 9% Ni steel for cryogenic use as a steel material, a welding method using the welding solid wire, and a weld metal formed by the welding method.

  A 9% Ni steel having a high yield strength and excellent cryogenic toughness is known as a high-strength steel used at a cryogenic temperature of about −196 ° C., which is the temperature of liquid nitrogen. 9% Ni steel is widely used as a material for storage tanks such as liquefied natural gas (LNG), liquid nitrogen, and liquid oxygen, or as related materials. Since the structures of the storage tank and related equipment are usually manufactured by welding, the weld metal of a welded joint formed by welding 9% Ni steel used as a base material, that is, a weld joint, is also used as a base. Excellent cryogenic toughness comparable to that of the material is required.

  Various studies have been made on the welding technology between 9% Ni steels. For example, if the base materials are welded using a common metal welding wire having the same component as the base material 9% Ni steel or a component similar to the base material, welding with excellent cryogenic properties It is thought that metal is obtained. Examples of welding methods include MIG welding using shield gas (Inert gas metal-arc welding), TIG welding (Inert gas tungsten-arc welding), and the use of MIG welding with higher welding efficiency than TIG welding is recommended. However, MIG welding has a problem that a high cryogenic toughness level cannot be secured stably. Therefore, when welding the base materials of 9% Ni steel using a common metal welding wire having the same or similar components, the welding is limited to TIG welding, which has a lower welding efficiency than MIG welding. The workability of construction is significantly reduced. Therefore, there has been almost no example of applying the common metal welding wire.

  On the other hand, a 9% Ni steel is welded to each other by MIG welding with high welding efficiency, using a Ni-based alloy having a relatively high Ni content of 60%, for example, INCONEL (registered trademark), as a welding wire, instead of the above-mentioned metal alloy welding wire. The way to do it is universal. The welded joint using the Ni-based alloy welding wire exhibits excellent toughness as it is welded even at an extremely low temperature of -196 ° C, while its strength, particularly 0.2% proof stress, is extremely low compared to 9% Ni steel. Become. As a result, the strength of the welded joint is lowered despite the high yield strength 9% Ni steel being used as the weld base material, and the design stress must be lowered accordingly. Specifically, in order to ensure high strength in the welded joint, there are disadvantages such as an increase in the thickness of the entire welded structure, an increase in weight, and an increase in expensive Ni-based alloy welding wires. In addition, when using a Ni-based alloy welding wire, there is a problem of hot cracking due to the addition of a large amount of Ni, and since the composition of the 9% Ni steel, which is the base material, and the weld metal are greatly different, The problem of thermal fatigue due to the difference in thermal expansion coefficient also becomes obvious.

  Therefore, despite the fact that the 9% Ni steel, which is the base material, has outstanding performance as a cryogenic steel, conventional welding wires represented by Ni-base alloys such as metal alloy welding wires and INCONEL are used. As long as it is used, due to the various problems described above, the excellent performance of the 9% Ni steel is not sufficiently exhibited, and its application range is significantly limited.

  In view of such problems, various techniques for improving a common metal welding wire having the same or similar composition as 9% Ni steel have been proposed. For example, Patent Document 1 describes a method devised so that particularly Ni steels for cryogenic temperatures can be firmly welded using Ni steel wires containing approximately the same amount of Ni. However, the above method has a problem that the number of welding processes increases. Moreover, the said method has stopped only the improvement of the partial cryogenic toughness of only the last weld layer in a welded joint. Therefore, it is not always an effective method for improving the cryogenic toughness of the entire weld metal.

  On the other hand, the present inventors have proposed the techniques of Patent Documents 2 to 4 in view of the above problems. In all of the above Patent Documents 2 to 4, 0.005 to 0.04% rare earth element (REM: Rare Earth Metal) is added to 9% Ni steel welding wire, and pinning particles that suppress grain growth By forming a fine REM oxide functioning as a weld metal in the weld metal, the cryogenic toughness and crack resistance strength of the weld metal are improved.

JP-A-53-118241 JP 2009-101414 A JP 2010-172907 A Japanese Patent No. 5244059

  According to Patent Documents 2 to 4, on average, good cryogenic toughness is obtained, but when joining by MIG welding, the toughness may be reduced due to poor fusion. Therefore, the cryogenic toughness varies and there is room for improvement in terms of stability.

  The present invention has been made in view of the above circumstances, and its purpose is to form a weld metal that exhibits stable and excellent cryogenic toughness without variation when 9% Ni steel as a base material is welded together. It is an object of the present invention to provide a welding solid wire capable of being welded, a method of forming a weld metal using the welding solid wire, and a weld metal excellent in the cryogenic toughness obtained by the method.

The solid wire for welding according to the present invention capable of solving the above problems is, in mass%, C: more than 0% and 0.10% or less, Si: more than 0% and 0.15% or less, Mn: 0.1 to 0 80%, Ni: 8 to 15%, Ti: 0.015 to 0.050%, REM: more than 0% to 0.005% or less, and O: more than 0% to 0.0065% or less, with the balance being It is iron and inevitable impurities, and has a gist where it satisfies the following formula (1).
10 ≦ 18 × [Mn] + 71 × [REM] + 206 × [Ti] ≦ 20 (1)
In the formula, [] represents mass% and represents the content of each element.

  In a preferred embodiment of the present invention, the solid wire for welding has a surface of the solid wire covered with a copper plating layer, and the mass ratio of the copper plating layer to the total mass of the solid wire is 0.1 to 0. .2%.

  In a preferred embodiment of the present invention, the solid wire for welding is a solid wire for welding used for gas shielded arc welding using a pulse power source, and the shielding gas contains 0% by volume or more and 2% by volume of carbon dioxide. Argon gas contained below.

  The present invention also includes a welding method, and the welding method is characterized in that a weld metal is formed by gas shield arc welding of a steel material using the solid wire for welding and a pulse power source.

  In preferable embodiment of this invention, the said welding method WHEREIN: The shielding gas used for the said gas shield arc welding is argon gas which contains a carbon dioxide gas in 0 volume% or more and 2 volume% or less.

  The present invention also includes a weld metal formed by any of the above-described welding methods.

  According to the solid wire for welding of the present invention, the chemical composition is appropriately controlled. Therefore, when 9% Ni steels are welded together, a weld metal that exhibits stable and excellent cryogenic toughness is formed without variation. be able to.

FIG. 1 is an explanatory view schematically showing an example of a butt-welded joint between 9% Ni steel plates showing a good bead shape in Examples. FIG. 1 is an explanatory view schematically showing an example of a butt-welded joint between 9% Ni steel sheets showing a bad bead shape in Examples. FIG. 3 is a schematic explanatory view showing a sampling position of a Charpy impact test piece of weld metal.

  In order to provide a solid wire for welding that can stably form a weld metal exhibiting good cryogenic toughness without variation when 9% Ni steels are welded to each other, The study was based on the four technologies. As a result, it has been newly found that when REM is added in excess of 0.005%, a weld defect is generated, the cryogenic toughness becomes unstable, and the characteristics vary. Therefore, as a result of further investigation, the upper limit of REM is 0.005% or less, which is smaller than that of the above-mentioned patent document, contains a predetermined amount of Ti, and is added as a deoxidizer and the above-mentioned REM It has been found that the intended purpose is achieved if the amounts of Ti and Mn are appropriately controlled as shown in formula (1). Furthermore, if the solid wire for welding of the present invention is used, even if 9% Ni steel plates are welded together by MIG welding with high welding efficiency, the excellent characteristics (high proof stress and excellent cryogenic toughness) of 9% Ni steel are obtained. The inventors have found that the above object can be achieved without impairing the present invention and completed the present invention.

  Hereafter, the chemical component composition which comprises the solid wire for welding of this invention is demonstrated in detail.

C: more than 0% and 0.10% or less C is an element effective in increasing the tensile strength (TS) of a weld metal even in a small amount. Therefore, an amount exceeding 0% is contained. The minimum with preferable C content is 0.01% or more, More preferably, it is 0.02% or more. On the other hand, if the C content is excessive, the cryogenic toughness of the weld metal is remarkably lowered, so the upper limit of the C content is 0.10% or less. Preferably it is 0.08% or less, More preferably, it is 0.06% or less.

Si: more than 0% and 0.15% or less Since Si acts effectively on the improvement of welding workability, it is contained in an amount exceeding 0%. The minimum with preferable Si content is 0.01% or more, More preferably, it is 0.02% or more. On the other hand, if the Si content is excessive, the cryogenic toughness of the weld metal is remarkably lowered, so the upper limit of the Si content is 0.15% or less. Preferably it is 0.12% or less, More preferably, it is 0.10% or less

Mn: 0.1 to 0.80%
Mn is an important basic component because it improves welding workability and exhibits excellent effects as a deoxidizer and sulfur scavenger. In order to effectively exhibit the above effects, the lower limit of the Mn content is set to 0.1% or more. The minimum with preferable Mn content is 0.2% or more, More preferably, it is 0.3% or more. However, when the Mn content is excessive, stable retained austenite is likely to be generated in the weld metal, and the cryogenic toughness of the weld metal is significantly impaired as in the case of excessively containing Ni described later. Therefore, the upper limit of the Mn content is 0.80% or less. The upper limit with preferable Mn content is 0.7% or less, More preferably, it is 0.6% or less.

Ni: 8-15%
Ni is an important component for ensuring good cryogenic toughness. In order to impart sufficient cryogenic toughness to the weld metal, the lower limit of the Ni content is 8% or more. A preferred lower limit is 9.0% or more, more preferably 10.0% or more. On the other hand, when the Ni content is excessive and exceeds 15%, the mechanical strength of the weld metal becomes too high, and the ductility is extremely lowered. Furthermore, unstable retained austenite is generated, which transforms to martensite at a very low temperature, leading to a decrease in cryogenic toughness. Therefore, the upper limit of Ni content is 15% or less. The upper limit is preferably 13.0% or less, more preferably 12.0% or less.

Ti: 0.015 to 0.050%
Ti improves welding workability by adding a small amount and exhibits an excellent effect as a deoxidizer. In addition, Ti is not as remarkable as REM described later, but forms a fine oxide like REM. Therefore, Ti can be included together with REM to improve the cryogenic toughness of the weld metal. In order to effectively exhibit such an effect, the lower limit of the Ti content is set to 0.015% or more. The minimum with preferable Ti content is 0.018% or more, More preferably, it is 0.020% or more. However, when the Ti content is excessive, TiC, which is a fine precipitate, is easily generated in the weld metal, and the cryogenic toughness is lowered. Therefore, the upper limit of Ti content is 0.050% or less. Preferably it is 0.045% or less, More preferably, it is 0.040% or less.

REM: more than 0% and 0.005% or less REM acts as a deoxidizer and reacts with a trace amount of oxygen contained in the weld metal to form fine REM oxide. Such a fine REM oxide does not act as a starting point for fracture, but rather functions as a pinning particle that suppresses the weld solidification process and crystal grain growth after solidification, thereby reducing the strength and cryogenic toughness of the entire weld metal. It works effectively to enhance. Therefore, the REM content is set to more than 0%. A preferable lower limit of the REM content is 0.002% or more. On the other hand, since REM also has the effect of concentrating arcs, it may cause welding defects and cause instability toughness. According to the examination results of the present inventors, when the REM content exceeds 0.005%, a penetration failure that promotes defects tends to occur, and the minimum value is small even if the average value of the cryogenic toughness is good. Thus, it has been found that stable high cryogenic toughness cannot be obtained. From the above viewpoint, the upper limit of the REM content is set to 0.005% or less. The upper limit with preferable REM content is 0.004% or less, More preferably, it is 0.003% or less. In the present invention, REM means 15 lanthanoid series rare earth elements from La to Lu in the periodic table. These elements may be added alone or in combination of two or more.

O: more than 0% and 0.0065% or less O is an element necessary for forming the fine REM oxide useful for improving the cryogenic toughness. Therefore, the O content is set to more than 0%. The lower limit of the O content is preferably 0.0020% or more. However, when the O content is excessive, coarse oxides are formed, which adversely affects the cryogenic toughness, so the upper limit is made 0.0065% or less. The upper limit with preferable O content is 0.0060% or less, More preferably, it is 0.0050% or less.

(1) Formula: 10 ≦ 18 × [Mn] + 71 × [REM] + 206 × [Ti] ≦ 20
In this invention, while satisfying the said component, it controls so that content of Mn, REM, and Ti which has a deoxidation effect may satisfy said (1) Formula. Thereby, the stability of the arc is improved and the oxide inclusions can be appropriately controlled. Furthermore, by controlling the above expression (1), the adverse effect of REM that affects the penetration shape can be avoided, and the stability of the cryogenic toughness is further ensured. If the value of the above formula (1) is less than 10, the deoxidation action by the above elements is insufficient, and the cryogenic toughness decreases in both the average value and the minimum value. Therefore, the lower limit of the value of the above equation (1) is 10 or more. The minimum with the preferable value of the said (1) Formula is 10.5 or more, More preferably, it is 11 or more. On the other hand, if the value of the above equation (1) exceeds 20, the arc becomes unstable, weld defects are likely to occur, and stable high cryogenic toughness cannot be obtained. Therefore, the upper limit of the value of the above equation (1) is set to 20 or less. The upper limit with the value of the said (1) formula is 19 or less, More preferably, it is 18 or less.

  The basic composition of the welding solid wire of the present invention is as described above, and the balance is iron and inevitable impurities. Examples of the inevitable impurities include Al, Ca, Cr, Mg, P, S, B, and N that are brought in depending on the status of raw materials, materials, manufacturing equipment, and the like. Since these elements tend to reduce the cryogenic toughness, it is preferable to reduce them as much as possible within the range of the steelmaking process by a regular method. Specifically, for example, Al is less than about 0.020%, Ca is less than about 0.002%, Cr is less than about 0.01%, Mg is less than about 0.002%, and P is less than about 0.015%. , S is preferably less than about 0.010%, B is less than about 0.002%, and N is preferably less than about 0.008%.

  The method for producing the solid wire for welding according to the present invention, the method for feeding the solid wire, and the method for modifying the surface of the solid wire are not particularly limited, and a method usually used in the technical field of the present invention can be appropriately employed. it can. For example, the method described in Patent Document 4 described above can be referred to. Hereinafter, although the preferable example is described, this invention is not limited to this.

  As a method for producing the solid wire for welding according to the present invention, for example, a metal alloy wire of the above-mentioned chemical composition is used to roll a die to a product diameter of 0.8 to 1.6 mmφ, for example. Or a method of drawing in a known drawing process using a hole die drawing apparatus.

  The welding solid wire manufactured in this way is wound in a spool or conveyed in a storage form filled in a pail pack, and is subjected to welding. The solid welding wire thus housed is pulled out of the spool or the pail pack by the feeding roller of the feeder at the welding construction site of the low-temperature structure made of 9% Ni steel. Thereafter, the sheet is fed to a power feed tip portion in a torch such as MIG welding at a welding position via a liner or the like included in a conduit cable which is a subsequent flexible guide tube. In such a series of welding solid wire feeding operations, the welding solid wire of the present invention is stably supplied at a constant speed regardless of the feeding conditions.

  In order to secure the wire feedability more stably, it is preferable to form a copper plating layer on the surface of the welding solid wire according to the present invention, or to apply a lubricant, rust preventive oil, or the like. According to such a surface modification method, the effect of improving the wire feedability by reducing the feed resistance from the feed liner can be obtained. Furthermore, it has the effect of greatly improving the drawability at the time of wire drawing and improving the electrical conductivity and rust prevention. There are no particular limitations on the method for forming the copper plating layer, the type of lubricant, rust-preventing oil, etc., and these coating methods, and known methods can be employed.

  Among the above, when a copper plating layer is formed on the surface of the solid wire for welding, the mass ratio of the copper plating layer to the total mass of the solid wire is 0.1 from the viewpoint of achieving both plating properties and cryogenic toughness. It is preferable that it is -0.2%. If the mass ratio is less than 0.1%, sufficient plating properties may not be obtained, and the wire feedability may not be improved. On the other hand, if it exceeds 0.2%, the Cu concentration in the weld metal increases, the strength becomes excessive, and the cryogenic toughness may not be ensured.

  However, the present invention is not intended to be limited to the above embodiment, and in consideration of environmental problems, it is also possible to apply a bare welding solid wire that does not apply the above-described copper plating layer, lubricant, rust preventive agent, etc. Of course it is possible.

  Moreover, the solid wire for welding of the present invention may have a single structure or a laminated structure. As the latter laminated structure, for example, a known coaxial multilayer wire structure can be adopted.

  The solid wire for welding according to the present invention has been described above.

  Next, the welding method of the present invention will be described. The welding method of the present invention is characterized by the use of the above-described solid wire for welding the 9% Ni steel which is a base material, thereby stably exhibiting a high level of cryogenic toughness. A metal is obtained.

  As described above, the base material used in the present invention is a 9% Ni steel material. The chemical component composition of the 9% Ni steel material is usually used in the field. In the present invention, since REM, Ti, and Mn in the welded solid wire are particularly controlled as described above, the above-mentioned components of 9% Ni steel that is the base material are also, for example, REM: more than 0% to 0.005% Hereinafter, it is preferable to control within a range of Ti: more than 0% and 0.05% or less and Mn: more than 0% and 1.5% or less.

  In particular, if the solid wire for welding of the present invention is used, it is useful in that the 9% Ni steels can be welded to each other without obstructing the original characteristics of the 9% Ni steels by MIG welding with high welding efficiency. is there. At that time, gas shield arc welding is preferably performed using a pulse power source instead of a steady DC power source as a welding power source; more preferably, Ar gas containing carbon dioxide in a range of 2% by volume or less as a shielding gas. It is useful to use Thereby, a good penetration shape, that is, a good bead shape can be secured. As described above, the present invention includes not only pure argon gas (100% Ar) normally used for MIG welding as a shielding gas but also an aspect in which carbon dioxide gas is contained in Ar gas in a range of 2% by volume or less. This is different from ordinary gas shielded arc welding.

  Hereinafter, preferred embodiments of the welding method according to the present invention will be described.

  The welding power source used in the present invention is not particularly limited, and a steady welding power source or a pulse power source can be used. However, if a pulse power supply is used, the droplet transfer tends to be sprayed, so that a good bead shape can be obtained as shown in the examples described later. The conditions for using the pulse power supply are not particularly limited, and a generally used method can be employed.

  Moreover, the shielding gas used for gas shield arc welding can accept | permit carbon dioxide gas in Ar gas, Preferably it is 2 volume% or less. It is confirmed in the examples described later that a better bead shape can be obtained while maintaining a good cryogenic toughness within this range. When the ratio of the amount of carbon dioxide exceeds 2% by volume, the amount of oxygen in the weld metal increases due to oxygen derived from the carbon dioxide gas, and there is a risk that good cryogenic toughness in the weld metal cannot be ensured. More preferably, it is 1.8 volume% or less, More preferably, it is 1.5 volume% or less.

  When performing gas shield arc welding, the shield gas is doubled, the outer gas is a pure argon atmosphere, and the inner gas is carbon dioxide as described above, preferably containing 2% by volume or less. Is also useful. By adopting such a configuration, air mixing during welding is suppressed as much as possible, and a weld metal having even better cryogenic toughness can be obtained.

  According to the above-described welding method of the present invention, a weld metal that is stable at a high level and has excellent cryogenic toughness can be obtained. The chemical composition of the weld metal obtained by the above method is basically the same as the chemical composition of the solid wire for welding. In addition, when it has a copper plating layer on the surface of the said solid wire for welding, the composition of the said copper plating layer is further reflected in the composition of a weld metal.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited by the following examples, and can be implemented with modifications within a range that can meet the purpose described above and below. They are all included in the technical scope of the present invention.

  Steel wires having the chemical composition shown in Table 1 were manufactured by vacuum melting, and a solid wire for welding having a product diameter of 1.2 mm was obtained by wire drawing. Among these, some of the solid wires for welding were subjected to copper plating. In addition, as a REM described in Table 1, a misch metal containing Ce: 50% and La: 25% by mass% was used.

  Using the welding solid wire thus produced, gas shielded arc welding was performed on the steel material having the chemical composition shown in Table 2 as a 9% Ni steel base material under the following welding conditions and the conditions shown in Table 3. Carried out. In this example, MIG welding was performed.

(Welding conditions)
Base material (steel) thickness: 25mm
Groove angle: 60 ° (V-shaped groove)
Route interval: 4mm
Welding posture: Downward shielding gas: Argon (Ar) gas +0 to 1.0 volume% carbon dioxide gas preheating / interpass temperature: 50 to 125 ° C.
Lamination method: 7-layer 16-pass welding current:
(1) 260-280A (steady DC power supply, wire plus)
Welding voltage: 23-31V
Welding speed: 24-27 cm / min
The welding current was changed according to the welding speed. Specifically, the current was changed so that the welding current was 260 A when the welding speed was 24 cm / min and the welding current was 280 A when the welding speed was 27 cm / min.
(2) Pulse power supply, wire plus peak current: 350A
Base current: 70A
Between one peak from the start of rising to the peak stationary period to the end of rising: 5 milliseconds The optimum welding voltage was selected according to the shield gas composition.

  The beat shape and Charpy impact absorption value of the weld metal thus obtained were evaluated as follows.

(Evaluation of bead shape)
The bead shape means a weld metal formed by each pass during welding. In this example, the bead shape of the weld metal was observed visually without performing the grinder process for each pass.

  As a result, as shown in FIG. 1, when a weld metal having a good bead shape was obtained, the bead shape was good and it was evaluated as “good”. Specifically, the height of the bead is low and gentle, and the side edge of the bead and the 9% Ni steel surface are connected smoothly and continuously. On the other hand, as shown in FIG. 2, when a weld metal having a good bead shape was not obtained, the bead shape was not good, and “bad” was evaluated. Specifically, the bead shape has a shape that bulges upward, and the side edge of the bead and the 9% Ni steel surface are connected by a discontinuous inflection point (bent part). .

(Evaluation of cryogenic toughness)
As shown in FIG. 3, three JIS Z 3111 No. 4 V-notch test pieces were collected as Charpy impact test pieces perpendicular to the weld line direction from the center of the plate thickness of the weld metal, and in accordance with JIS Z 2242, A Charpy impact test at −196 ° C. was performed, and the Charpy impact absorption value (vE ₋₁₉₆ ) was measured. When the average value of the three Charpy impact absorption values was 100 J or more, it was evaluated that the cryogenic toughness was excellent.

  Furthermore, when the minimum value of the absorbed energy in the Charpy impact test was 100 J or more, it was evaluated that the stability of the cryogenic toughness was excellent.

  These results are also shown in Table 3.

  First, focusing on cryogenic toughness, it can be considered as follows. Test No. in Table 3 1 to 15 are Nos. 1 in Table 1 that satisfy the requirements defined in the present invention. It is an example in which a weld metal is formed using solid welding wires of A1 to A10, and it can be seen that all are stable and excellent in cryogenic toughness.

  On the other hand, test no. 16-25 is an example which does not satisfy any requirement prescribed | regulated by this invention, and cryogenic toughness and at least one of the stability fell.

  For details, see Test No. No. 16 is a solid wire No. 1 in Table 1 with excessive C content. It is the example which formed the weld metal using B1. As a result, the cryogenic toughness and stability decreased.

  Test No. No. 17 is a solid wire No. 1 in Table 1 with excessive Si content. This is an example in which a weld metal is formed using B2. As a result, the cryogenic toughness and stability decreased.

  Test No. No. 18 is a solid wire No. 1 in Table 1 having an excessive Mn content. This is an example in which a weld metal is formed using B3. As a result, the cryogenic toughness and stability decreased.

  Test No. No. 19 is a solid wire No. 1 in Table 1 having a low Ni content. This is an example in which a weld metal is formed using B4. As a result, the cryogenic toughness and stability decreased.

  Test No. No. 20 is a solid wire No. 1 in Table 1 with excessive Ni content. In this example, a weld metal is formed using B5. As a result, the cryogenic toughness and stability decreased.

  Test No. No. 21 is a solid wire No. 1 in Table 1 with excessive REM content. It is the example which formed the weld metal using B6. As a result, the stability of the cryogenic toughness decreased.

  Test No. No. 22 is a solid wire No. in Table 1 having a low Ti content. In this example, a weld metal is formed using B7. As a result, the cryogenic toughness and stability decreased.

  Test No. No. 23 is a solid wire No. 1 in Table 1 having an excessive Ti content. It is the example which formed the weld metal using B8. Therefore, low temperature toughness and stability were reduced.

  Test No. No. 24 is a solid wire No. 24 in Table 1 having an excessive O content and a low value of the expression (1). In this example, a weld metal is formed using B9. Since the O content is large, the cryogenic toughness is lowered, and the stability is lowered because the value of the formula (1) is low.

  Test No. No. 25 is a solid wire No. in Table 1 having a large value of the expression (1). In this example, a weld metal is formed using B10. As a result, the stability of the cryogenic toughness decreased.

  Further, focusing on the bead shape, when the amount of carbon dioxide in the shield gas in the inner is controlled to 2% by volume or less, the test No. 1 using a steady DC power source was used. 1 to 3, 13 to 16, 21, 24 Test No. using a pulse welding power source. In 4-12, 17-20, 22, 23, 25, a good bead shape was obtained.

1a, 1b Welded joint 2a, 2b 9% Ni steel plate 3, 4 Welded metal 5 Backing material

Claims (6)

% By mass
C: more than 0% and 0.10% or less,
Si: more than 0% and 0.15% or less,
Mn: 0.1 to 0.80%,
Ni: 8-15%,
Ti: 0.015 to 0.050%,
REM: more than 0% and 0.005% or less, and O: more than 0% and 0.0065% or less,
The balance is iron and inevitable impurities,
Solid wire for welding characterized by satisfying the following formula (1).
10 ≦ 18 × [Mn] + 71 × [REM] + 206 × [Ti] ≦ 20 (1)
In the formula, [] represents mass% and represents the content of each element.   The solid wire for welding according to claim 1, wherein a surface of the solid wire is covered with a copper plating layer, and a mass ratio of the copper plating layer to a total mass of the solid wire is 0.1 to 0.2%. .   The solid wire for welding used for gas shielded arc welding using a pulse power source, wherein the shielding gas is argon gas containing carbon dioxide in an amount of 0% by volume to 2% by volume. Solid wire for welding.   A welding method comprising forming a weld metal by gas shield arc welding of a steel material using the solid wire for welding according to claim 1 or 2 and a pulse power source.   The welding method according to claim 4, wherein the shielding gas used for the gas shielded arc welding is an argon gas containing carbon dioxide gas in an amount of 0% by volume to 2% by volume.   A weld metal formed by the welding method according to claim 4 or 5.