JP2002331387A - Welding wire for highly touch martensite based-stainless steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a welding material made of martensite based-stainless steel as a welding material used when the martensite based-stainless steel is welded, not developing a high temperature crack and a low temperature crack, and capable of obtaining a welding part excellent in toughness, strength and corrosion resistance. SOLUTION: The welding wire for the highly touch martensite based-stainless steel contains, in terms of mass%, C: 0.005-0.12%, Si: 0.01-1.0%, Mn: 0.02-2.0%, Cr: 11.0-14.0%, Ni: 7.0-10.0%, Mo: 3.0 or less, Al: 0.02-0.05%, Mg: 0.005-0.01%, and Ti: 0.005-0.5%, N: 0.001-0.1%, limits to P: 0.03% or less, and S: 0.01 or less, satisfies Ti×N>=0.0005, 1.8<=Cr equivalent/Ni equivalent <= 2.8 and 100<=Cr equivalent × Ni <= equivalent 150, and the residue comprises Fe and unavoidable impurities.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a martensitic stainless steel which is used for applications such as line pipes for transporting oil and natural gas and pressure vessels for storage, and in particular, is required to have strength, toughness and corrosion resistance. More specifically, when welding such a martensitic stainless steel, a weld metal excellent in strength, toughness and corrosion resistance can be obtained, as well as hot cracking and low temperature during welding. The present invention relates to a welding wire for martensitic stainless steel that can suppress cracking.

[0002]

2. Description of the Related Art In general, line pipes for transporting oil and natural gas and pressure vessels for storage are connected and manufactured by welding. For this reason, as the mechanical properties of these base materials and welds, strength and toughness against high pressure for improving transport or storage capacity, and corrosion resistance against corrosive environments such as wet carbon dioxide gas and hydrogen sulfide are required. At the same time, excellent weldability free of hot cracks and cold cracks during welding is also required.

[0003] As a steel material suitable for such a line pipe or a pressure vessel, Cr is generally used in order to obtain corrosion resistance.
It contains about 1 to 15%, reduces the C content to improve weldability, further adds an austenite forming element to ensure strength and toughness, and performs quenching-tempering heat treatment to reduce the structure. Tempered martensite-made steel or steel pipe is known. For example, JP-A-4-99154, JP-A-4-99155, and JP-A-9-256115 reduce C and N, There has been proposed a martensitic stainless steel to which a substitution type austenite stabilizing element is added and which has excellent weldability.

Conventionally, welding materials used for welding the above martensitic stainless steel include “NK”.
K Technical Report ", 1989, No. 129, Nos. 15-22
On the page, when preparing a TIG welded joint (equivalent to local circumferential welding of a line pipe) using a UOE steel pipe of AISI 410 steel, a co-metallic material of martensitic stainless steel with Ni added as a welding material was used. Examples have been reported. However, as can be seen in the same document, in a co-metallic material of martensitic stainless steel, even if a large amount of Ni is contained, the hardness of the weld metal becomes very hard and the susceptibility to low-temperature cracking increases, Pre-heat treatment or post-heat treatment is indispensable at the time of welding, and there has been a problem that workability at the time of welding is deteriorated and construction cost is increased.

On the other hand, in general, when welding is performed using a welding material for a high Ni austenitic stainless steel or a welding material for a Ni-based superalloy, selective corrosion of a weld does not occur, corrosion resistance is excellent, and weld metal is excellent. Has low hardness and can secure toughness.

However, the welding material for austenitic stainless steel and the welding material for Ni-base superalloy have a problem that the strength of the weld metal is reduced due to the crystal structure. If the strength of the weld metal is very low compared to the strength of the base metal of martensitic stainless steel, when external stress is applied to the welded structure such as a steel pipe, the weld metal in the weld will be intensively deformed and break. (Undermatching).

[0007] Accordingly, even when a conventional welding material for austenitic stainless steel or a welding material for high Ni alloy is used as a welding material for welding martensitic stainless steel, the strength of the welded portion can be reduced. There is a problem in point. In addition, in recent years, welding materials for duplex stainless steel, which are frequently used, are also often under-matched because the strength of the weld metal is similarly low.

In order to improve the problems of these conventional welding materials for martensitic stainless steel, the present inventors have disclosed the above-mentioned Japanese Patent Application Laid-Open Nos. 10-146691 and 2-14.
Japanese Patent Application Laid-Open No. 000-15447 proposes a welding wire in which the structure of the weld metal has a three-phase structure of an austenite phase + a ferrite phase + a martensite phase. There is a need for the development of welding materials that can improve toughness.

[0009]

In view of the above-mentioned problems of the prior art, the present invention provides a welding material used for welding martensitic stainless steel without performing preheating and post-heating during welding. It is an object of the present invention to provide a welding material made of martensitic stainless steel, which does not cause high temperature cracking or low temperature cracking of a welded portion and provides a welded portion having excellent toughness, strength and corrosion resistance.

[0010]

The present invention solves the above-mentioned problems, and the gist of the invention is as follows.

(1) C: 0.005 to 0.5% by mass
12%, Si: 0.01-1.0%, Mn: 0.02-
2.0%, Cr: 11.0 to 14.0%, Ni: 7.0
１10.0%, Mo: 3.0% or less, Al: 0.002
-0.05%, Mg: 0.0005-0.01%, T
i: 0.005 to 0.5%, N: 0.001 to 0.1%
, P: 0.03% or less, S: 0.01% or less, and satisfy the following formulas (1), (2) and (3), with the balance being Fe and inevitable impurities. A welding wire for high-toughness martensitic stainless steel, comprising: Ti × N ≧ 0.0005 ・ ・ ・ (1) 1.8 ≦ Cr equivalent / Ni equivalent ≦ 2.8 ・ ・ (2) 100 ≦ Cr equivalent × Ni equivalent ≦ 150 ・ ・ ・ (3) where Cr Equivalent (% by mass) = Cr% + Mo% + 1.5 × Si
%, Ni equivalent (mass%) = Ni% + 0.5 × Mn% + 30 ×
C%, Cr%, Mo%, Si%, Ni%, Mn%, and C% indicate the contents of Cr, Mo, Si, Ni, Mn, and C, respectively.

(2) Further, in mass%, Cu: 0.1
The high-toughness martensitic stainless steel welding wire according to the above item (1), which contains one or two of Nb: 0.01 to 0.5%. .

(3) The above-mentioned item (1) or (2), wherein the microstructure of the weld metal obtained by gas shielded arc welding is a three-phase structure of an austenite phase + a ferrite phase + a martensite phase. The welding wire for high toughness martensitic stainless steel according to any one of the above.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors carried out gas shielded arc welding using a welding wire for martensitic stainless steel to which martensitic stainless steel is added with various components. The relationship between the strength, toughness, corrosion resistance, low-temperature cracking resistance, and high-temperature cracking resistance and the weld metal structure was investigated.

As a result, in order to simultaneously satisfy the combined required characteristics of strength, toughness, corrosion resistance, low-temperature cracking resistance and high-temperature cracking resistance of the weld metal, the microstructure of the weld metal must be austenitic phase + ferrite phase + martensite. In addition to the three-phase structure of the phases, in order to further improve the toughness of the weld metal, the component system of the weld metal is a component system in which solidification is completed with a single ferrite phase, and Mg and Ti are added as a composite, And by controlling the relationship between Ti and N amount,
It became clear that it is effective to make the equiaxed crystal and refine the weld metal.

The present invention has been made based on these findings, and the details of the present invention will be described below.

The following "%" means "% by mass" unless otherwise specified.

First, the microstructure of the weld metal according to the present invention will be described.

The microstructure of the weld metal has a three-phase structure of austenite phase + ferrite phase + martensite phase in order to simultaneously satisfy the combined required properties of strength, impact toughness, corrosion resistance, low temperature cracking resistance and high temperature cracking resistance. It is necessary to If the weld metal structure is a ferrite single phase, the impact toughness is poor and the strength is insufficient. When the weld metal structure is an austenitic single phase, there is a high risk of hot cracking and the strength is extremely low. If the weld metal structure is martensite single phase, the impact toughness is poor and there is a risk of low temperature cracking. If the weld metal structure is a two-phase structure of a ferrite phase and an austenite phase, the crack resistance and toughness are good, but the strength is insufficient. When the weld metal structure is a two-phase structure of a ferrite phase and a martensite phase, the susceptibility to low-temperature cracking is high and the impact toughness is poor. A hot metal cracking susceptibility is high in a two phase structure of an austenitic phase + a martensite phase as a weld metal structure.

In the present invention, the toughness and low-temperature cracking resistance are austenite, the strength is martensite, and the high-temperature cracking resistance is obtained by forming the weld metal structure into a three-phase structure of austenite phase + ferrite phase + martensite phase. Since each is secured by ferrite, the strength and toughness of the weld metal are increased, high-temperature cracking is prevented, and the occurrence of low-temperature cracking is suppressed without performing preheating or post-heat treatment.

Therefore, in the present invention, it is necessary that the weld metal structure has a three-phase structure of an austenite phase + a ferrite phase + a martensite phase.

Next, the refinement of crystal grains in the weld metal structure for the purpose of improving the toughness of the weld metal will be described.

In general, stainless steels are classified into component systems in which the primary solidification phase is a ferrite phase or an austenite phase according to their component systems. Solidification is completed in two phases.

TiN and Mg-based inclusions (MgO-Al
₍ Including ₂ O ₃ spinel phase) has very good lattice matching with the ferrite phase, so that it becomes a solidification nucleus of the ferrite phase,
The effect of making the ferrite phase equiaxed and the stable formation of the primary ferrite phase are promoted, which is effective for refining ferrite crystal grains during solidification.

On the other hand, TiN and Mg-based inclusions hardly become solidified nuclei in the austenite phase because of poor lattice matching with the austenite phase. The liquid phase /
Since the interfacial energy between the austenite phase is larger than the interfacial energy between the liquid phase and the ferrite phase, the austenite phase is not easily formed on the ferrite phase, and the austenite phase grows independently of the generation and growth of the ferrite phase.

Therefore, in the present invention, TiN and Mg-based inclusions are used as solidification nuclei of the ferrite phase to promote the equiaxed crystallization of the ferrite phase and the stable formation of the primary ferrite phase, thereby reducing the ferrite crystal grains during solidification. Therefore, it is necessary to limit the component system of the weld metal to a component system in which the primary solidification phase is a ferrite phase and the solidification is completed with a ferrite single phase.

In a component system in which the weld metal forms a two-phase solidification of a primary ferrite phase and an austenite phase, even if the ferrite phase is equiaxed, the austenite phase grows independently of the formation and growth of the ferrite phase. Therefore, the austenite phase is columnar crystal solidified, and the austenite phase and the martensite phase formed by transformation from the austenite phase are not sufficiently refined.

As a result of the experiments by the present inventors, the primary solidification phase of the weld metal is a ferrite phase, and the component system that completes solidification with a single ferrite phase is calculated by the following equations (5) and (6). In the relationship between the Cr equivalent and the Ni equivalent, if the component system satisfies the following formula (4), solidification is completed with the primary solidification phase of the weld metal being the ferrite phase and the ferrite single phase. The ratio of Cr equivalent / Ni equivalent is 1.8 or more (4) where Cr equivalent (% by mass) = Cr% + Mo% + 1.5 × Si% (5) Ni equivalent (% by mass) = Ni% + 0.5 × Mn% + 30 × C% (6)

In the present invention, in order to refine the solidified crystal grains of the weld metal, the primary ferrite phase is a ferrite phase, and in a component system in which solidification is completed with a single ferrite phase, the primary ferrite is It is necessary to form Ti nitride before solidification. For that purpose, according to the experiments of the present inventors, the temperature at which the primary ferrite phase solidifies (liquidus temperature).
Ti content and N so that Ti nitride crystallizes out at higher temperature
The content may be limited, and by controlling the components so as to satisfy the relationship of the following formula (1), Ti nitride is surely generated before the primary ferrite is solidified, and the effect of refining the solidified crystal grains is reduced. can get. Ti × N ≧ 0.0005 ・ ・ ・ (1)

As described above, according to the present invention, the primary solidification phase of the weld metal is a ferrite phase, and the ferrite single phase is used as a component system to complete solidification, and the Ti nitride is reliably solidified before the primary ferrite solidifies. In order to refine the solidified crystal grains of the weld metal by generating and improve toughness,
Cr equivalent / Ni equivalent ≧ 1.8 and Ti × N ≧ 0.00
05 is an important requirement.

First, the reasons for limiting the components of the welding material and their contents in the present invention are described below.

C: C is added in an amount of 0.005% or more as an element for greatly increasing the strength of the weld metal and as an austenite forming element. C is an element that forms Cr carbides to reduce the corrosion resistance, but the C content is 0.1%.
If it is 12% or less, the decrease in corrosion resistance due to the addition of C is not so large, and does not fall below the corrosion resistance of martensitic stainless steel as a base material. However, if the C content exceeds 0.12%, the corrosion resistance and toughness of the weld metal decrease, so the upper limit is made 0.12%.

Si: Although Si is effective as a deoxidizing agent and a strengthening element for a weld metal, if its content is less than 0.01%, its deoxidizing effect is not sufficient, and conversely, it exceeds 1.0%. Even if contained, the effect not only saturates, but also lowers the impact toughness.
Limited to 1.0%.

Mn: Mn is necessary as a deoxidizing agent for the weld metal, and is also important as an austenite-forming element for adjusting the structure of the weld metal.
It is necessary to contain the above. However, even if the content exceeds 2.0%, the effect is no longer saturated, and the excessive addition of Mn reduces the hot workability and causes difficulty in the production of the material. And the upper limit content is 2.0%.

Cr: In order to ensure the corrosion resistance and strength of the weld metal, it is necessary to contain Cr in an amount of 11.0% or more.
If the content exceeds 0%, it is difficult to form a martensite structure for securing the strength of the weld metal. Therefore, the content of Cr is set to 11.0 to 14.0%.

Ni: Ni is important as an element for stably forming an austenite phase in the structure of the weld metal and ensuring toughness and corrosion resistance. If the content is less than 7.0%, the impact toughness is insufficient. Conversely, when the content of Ni is 10.
If it exceeds 0%, the primary solidification phase becomes an austenite phase, so that high-temperature welding cracks are likely to occur, and the austenite fraction becomes excessive, resulting in a decrease in the strength of the weld metal. Therefore, the content of Ni is set to 7.0 to 10.0%.

Mo: Mo is added in order to secure the corrosion resistance and high strength of the weld metal, but if it exceeds 3.0%, an intermetallic compound is formed in the weld metal and the toughness is reduced. The upper limit of the content is 3.0%.

Al: Al is an element required in the deoxidation step, and is also effective for improving the hot workability of steel. Further, by forming a MgO-Al ₂ O ₃ spinel phase becomes solidified nuclei coexisting with Mg, thereby improving toughness finer weld metal structure. 0.002% exerts this effect, and the lower limit is set. Further, when added in a large amount, Al oxide is generated in a large amount and mechanical properties are deteriorated, so the upper limit is 0.05%.

Mg: Mg forms Mg-based inclusions to become solidification nuclei, refines the weld metal structure, and improves toughness.
When added in combination with Ti, the effect is further improved. This effect is exerted at 0.0005%, which is the lower limit. Further, even if a large amount is added, the effect is saturated and a problem such as a decrease in corrosion resistance occurs.
Is the upper limit. Mg-based inclusions include oxides and sulfides such as M
The refinement of the solidified crystal grains and the weld metal as long as it is a compound containing g is effective, even MgO-Al ₂ O ₃ spinel phase has the same effect.

Ti: Ti forms Ti nitrides to become solidification nuclei, refines the weld metal structure, and improves toughness.
The effect is further improved by adding in combination with Mg. Since this effect is exhibited at 0.005% or more, the lower limit is set. However, if added in excess of 0.5%, the hot workability is reduced, so this is made the upper limit.

N: N forms Ti nitride and becomes a solidification nucleus, refines the weld metal structure and improves the toughness. This effect is exhibited at 0.001% or more, and the lower limit is set. Further, if added in a large amount, it hardens to impair workability and also decreases toughness, so the upper limit is 0.1%.

P: If P is present in a large amount, it reduces the hot cracking resistance and toughness of the weld metal. Therefore, it is desirable that P is small, and it is necessary to reduce it to 0.03% or less.
The smaller the better, the better.

S: If a large amount of S is also present, the resistance to high temperature cracking, hot workability, ductility and corrosion resistance is reduced. In order to further improve the manufacturability as a welding material and further improve the corrosion resistance of the weld metal, it is preferable to reduce S to 0.005% or less.

Ti × N: In order to refine solidified crystal grains and weld metal structure and improve toughness, it is necessary to form Ti nitride before primary ferrite is solidified.
For that purpose, according to experiments by the inventors, it is necessary to limit the Ti content and the N content so that Ti nitride is crystallized at a temperature higher than the temperature at which the primary ferrite phase solidifies (liquidus temperature). As shown in the equation (1), Ti × N is 0.00
If it is 05 or more, Ti nitride is surely generated before the primary ferrite solidifies, so this is the lower limit.

Cr equivalent / Ni equivalent: When the Cr equivalent / Ni equivalent is less than 1.8, two-phase solidification of primary ferrite phase + austenite phase occurs, and TiN and Mg-based inclusions (M
gO-Al ₂ O ₃ containing spinel phase) of the ferrite phase in the crystal nucleus is solidified equiaxed austenite phase,
The austenite phase and the martensitic phase formed by transformation from the austenite phase are not sufficiently refined and the toughness is not improved irrespective of the formation and growth of the ferrite phase. If it exceeds 2.8, the content of the ferrite phase increases, and the toughness decreases. Therefore, as shown in equation (2), the ratio of Cr equivalent / Ni equivalent is limited to 1.8 to 2.8.

Cr equivalent × Ni equivalent: When the Cr equivalent × Ni equivalent is less than 100, the content of the martensite phase in the weld metal increases, so that the impact toughness decreases. Also, 150
On the contrary, since the content of the martensite phase decreases on the contrary,
Strength decreases. Therefore, as shown in equation (3), Cr
The equivalent × Ni equivalent is limited to 100 to 150.

The above is the essential requirement of the welding wire for martensitic stainless steel of the present invention. In the present invention, the following elements can be further added as needed to further improve the characteristics. It is.

Cu: Cu has a remarkable effect on enhancing the strength and corrosion resistance of the weld metal, and is added in an amount of 0.1% or more as an austenite-forming element for securing toughness. %, The effect is no longer saturated, but the productivity of the welding material is reduced. Therefore, the upper limit content is set to 2.0% or less.

Nb: Nb combines with C to suppress the precipitation of Cr carbide and improve corrosion resistance. The addition of 0.01% or more is effective, but the addition of more than 0.5% lowers the ductility and toughness, so the upper limit content is set to 0.5%.

[0050]

EXAMPLES The effects of the present invention will be described below using examples of the present invention.

Using a 14.5 mm thick martensitic stainless steel plate having the composition shown in Table 1, a groove having a groove angle of 60 ° and a root surface of 1 mm was formed at the end.

The steel sheet having the composition shown in Table 1 was subjected to quenching-tempering heat treatment, and had a yield strength of 710 N / mm ^2.
The above is the steel plate.

The welding wire used for welding was produced by melting a steel having the composition shown in Table 2 by vacuum melting and drawing by a usual method.

A steel sheet having the composition shown in Table 1 was prepared using a welding wire having the composition shown in Table 2 under the conditions of a welding current of 200 A, a welding voltage of 24 V and a welding speed of 40 cm / min.
G welding was performed. In any case, no preheating was performed at the time of welding, and no heat treatment was performed after welding.

[0055]

[Table 1]

[0056]

[Table 2]

In Table 2, the Cr equivalent (% by mass) is shown.
= Cr% + Mo% + 1.5 × Si%, Ni equivalent (mass%) = Ni% + 0.5 × Mn% + 30 × C%, where C
r%, Mo%, Si%, Ni%, Mn%, and C% indicate the contents (% by mass) of Cr, Mo, Si, Ni, Mn, and C, respectively.

After welding, in order to evaluate the microstructure of the weld metal of the welded joint, a section of each welded joint was etched, and the developed welded structure was observed. In addition, JIS No. 4 impact test pieces (full size) were sampled so that the notch was located in the weld metal of each welded joint, and an impact test was performed to evaluate toughness. Also, in the direction perpendicular to the welding line, the JIS is to be included so that the parallel part includes the weld metal, the weld heat affected zone, and the base metal.
A No. 5 tensile test piece was sampled and subjected to a tensile test at room temperature to evaluate the strength. In addition, a test piece was taken from the weld metal of each welded joint, and a corrosion test was performed in a wet carbon dioxide gas environment to evaluate the corrosion resistance. As a corrosion test condition in a wet carbon dioxide gas environment, the sample was immersed in a 5% NaCl aqueous solution for 30 days in an autoclave at a test temperature of 120 ° C. and a carbon dioxide gas pressure of 40 atm. . In addition, JIS Z 3
155, and the U-type weld crack test described in JIS Z 3157 was adopted for the low-temperature crack test, and the hot crack resistance and the low-temperature crack resistance were evaluated, respectively. Table 3 shows the microstructure of the weld metal and the results of each test evaluation. In addition, in the results of the hot crack test and the cold crack test in Table 3, ○ indicates that no crack was observed,
X indicates that a crack occurred. In the results of the impact test, ○ indicates that the absorbed energy at −30 ° C. is 80.
J indicates that the value was 40 to 80 J, and X indicates that the value was 40 J or less. In the tensile test results,
Indicates that the fracture occurred at the base metal portion and did not fracture at the weld metal portion, and x indicates that the fracture occurred at the weld metal portion. In the corrosion test results, when the corrosion rate of a certain material in an environment is generally less than 0.1 mm / y, it is considered that the material is sufficiently corrosion-resistant and can be used. Less than 0.1 mm / y, x is 0.1 m
m / y or more is shown.

[0059]

[Table 3]

As is clear from Table 3, No. 2 was welded using a welding material having a component composition within the range of the present invention. In the invention examples 1 to 4, the weld metal structure has a three-phase structure of an austenite phase + a ferrite phase + a martensite phase, and each phase is refined, so that no preheating or post heat treatment is performed during welding. However, the weld metal has good hot crack resistance and low temperature crack resistance, excellent weld metal impact toughness, high weld metal strength (no break in the weld metal), and excellent weld metal corrosion resistance. All the complex requirements were satisfied at the same time.

On the other hand, No. 1 was welded using a welding material having a component composition outside the range of the present invention. Comparative Example 5 is
The weld metal becomes a ferrite single phase, and the impact toughness of the weld metal is extremely poor and the strength is low.

No. 2 was welded using a welding material having a component composition outside the scope of the present invention. 6 and no. In Comparative Example 10, welding hot cracking occurred because the weld metal became austenite single phase solidified. In addition, No. In Comparative Example No. 6, the strength of the weld metal was low. In Comparative Example No. 10, the toughness and strength of the weld metal are low.

No. 1 was welded using a welding material having a component composition outside the scope of the present invention. 7 and No. 7 Comparative Example 9 is
The weld metal has a single phase of martensite or a two-phase structure of martensite + ferrite, causing low-temperature cracking of the weld metal, and further significantly reduces the impact toughness of the weld metal. In addition, No. Comparative Example 7 has low corrosion resistance.

The welding was performed using a welding material having a component composition outside the scope of the present invention. In Comparative Example No. 8, the weld metal had a two-phase structure of ferrite + austenite, and the weld metal was excellent in crack resistance, toughness, and corrosion resistance, but the weld metal was broken due to insufficient strength. In addition, No. 1 was welded using a welding material having a component composition outside the scope of the present invention. 11, 1
In Comparative Examples 2 and 13, the weld metal was austenitic +
It became a three-phase structure of ferrite + martensite.
o. In Comparative Example 11, TiN serving as a core of a ferrite phase was used.
Each phase remained coarse because the Mg-based inclusions did not crystallize, and the toughness of the weld metal was reduced. Also,
No. In Comparative Example 12, TiN and Mg-based inclusions crystallized and the ferrite phase was refined, but the Cr equivalent / Ni
Since the equivalent ratio was small, the weld metal structure became two-phase solidification of ferrite + austenite, and the toughness of the weld metal was low because the austenite phase and the martensite phase remained coarse. No. In the comparative example of No. 13, although the weld metal became single-phase ferrite solidified and each phase was refined,
Since the equivalent ratio / Ni equivalent ratio was large, the weld metal structure had a large ferrite content, and the toughness of the weld metal was insufficient.

[0065]

According to the present invention, as a welding material used for welding martensitic stainless steel, it has excellent hot cracking resistance and low temperature cracking resistance without requiring preheating and post heat treatment during welding. In addition, it is possible to provide a welding wire for martensitic stainless steel from which a weld metal excellent in toughness, strength and corrosion resistance can be obtained, and it can be said that the industrial value is extremely large.

Claims (3)

[Claims] C: 0.005 to 0.12 by mass%
%, Si: 0.01 to 1.0%, Mn: 0.02 to 2.
0%, Cr: 11.0 to 14.0%, Ni: 7.0 to 1
0.0%, Mo: 3.0% or less, Al: 0.002 to
0.05%, Mg: 0.0005 to 0.01%, Ti:
0.005 to 0.5%, N: 0.001 to 0.1%, P: 0.03% or less, S: 0.01% or less, and the following formula (1): A welding wire for high-toughness martensitic stainless steel, which satisfies the formulas (2) and (3), and the balance consists of Fe and inevitable impurities. Ti × N ≧ 0.0005 ・ ・ ・ (1) 1.8 ≦ Cr equivalent / Ni equivalent ≦ 2.8 ・ ・ (2) 100 ≦ Cr equivalent × Ni equivalent ≦ 150 ・ ・ ・ (3) where Cr Equivalent (% by mass) = Cr% + Mo% + 1.5 × Si
%, Ni equivalent (mass%) = Ni% + 0.5 × Mn% + 30 ×
C%, Cr%, Mo%, Si%, Ni%, Mn%, and C% indicate the contents of Cr, Mo, Si, Ni, Mn, and C, respectively. 2. Further, in mass%, Cu: 0.1-2.
0%, Nb: one or two of 0.01 to 0.5%
The welding wire for high-toughness martensitic stainless steel according to claim 1, comprising a seed. 3. The method according to claim 1, wherein the microstructure of the weld metal obtained by gas shielded arc welding has a three-phase structure of austenite phase + ferrite phase + martensite phase. Welding wire for high toughness martensitic stainless steel.