JP4699161B2 - Austenitic stainless steel welding wire with excellent low temperature toughness and seawater corrosion resistance - Google Patents

Description

  The present invention relates to a welding wire for high corrosion resistance austenitic stainless steel used in marine / gulf environments and chloride environments, and in particular, welds the outer shell, bulkhead, aggregate, hydrofoil, etc. of a hull structure with stainless steel. The present invention relates to a welding wire for a highly corrosion-resistant austenitic stainless steel that can provide a weld metal having excellent pitting corrosion resistance and crevice corrosion resistance in a seawater environment and excellent low-temperature toughness.

  In general, austenitic stainless steel is used in an environment where corrosion resistance is required, SUS304 specified by JIS, SUS316 and SUS317 containing a large amount of Ni and Mo in order to improve corrosion resistance against non-oxidizing acids, grain resistance There are SUS304L, SUS316L and SUS317L in which C is reduced in order to improve the field corrosion resistance, and these steel types are selected and used depending on the corrosive environment.

  Moreover, as a welding wire used when these austenitic stainless steels are welded, a wire for austenitic stainless steel specified in JIS Z 3321 and a flux containing austenitic stainless steel specified in JIS Z 3323 are used. Many wires are used. Further, flux-cored wires for 308, 316, 308L, 316L austenitic stainless steel are also used (see, for example, Patent Documents 1 and 2).

  On the other hand, especially Cr, Mo, Cu, N are included in order to increase seawater corrosion resistance, and the contents of Mo and N are increased more than before to improve pitting corrosion resistance and crevice corrosion resistance. For example, high corrosion resistance stainless steels such as SUS836L and SUS890L have been developed.

  As a welding material used when welding these high corrosion resistance stainless steel and high seawater corrosion resistance stainless steel, Mo: 6.0 to 7.0%, N: 0.25 to 0.50%, Cr: 21 High Mo-high N-based TIG and plasma welding wires for high corrosion resistance stainless steel welding containing 0.5 to 25.0%, Ni: 17.5 to 20%, Cu: 0.5 to 1.0% (for example, Patent Document 3), Mo: 2.4 to 6.7%, N: 0.05 to 0.30%, Cr: 18.6 to 28.9%, Ni: 12.7 to 27.3% A high Mo-high N flux cored wire for welding high corrosion resistance stainless steel containing Cu: 0.8 to 2.4% has been proposed (for example, see Patent Document 4).

  In addition, there is a case where high corrosion resistance stainless steel is welded by using a high Cr-high Mo system Ni alloy wire such as Inconel 625 (60Ni-22Cr-9Mo-3.5Nb) without using these co-metal wires. It was.

  When welding highly corrosion-resistant stainless steel using the high Mo-high N-based welding wire and the high Cr-high Mo-based Ni alloy wire, the seawater corrosion resistance of the weld metal is sufficiently ensured. However, there is a problem that a brittle phase such as a sigma phase is precipitated in the weld metal due to the thermal cycle by welding, and the toughness of the weld metal is remarkably lowered, and this problem is particularly noticeable as the Mo content in the wire increases. (For example, see Non-Patent Document 1).

  Generally, these welding wires for austenitic stainless steels have a ferrite phase of about several to 10% by volume in the welded structure by welding from the viewpoint of weldability, that is, from the point of preventing high-temperature solidification cracking of the weld metal. The components are designed so as to obtain a weld metal containing. However, a weld metal containing a ferrite phase in the weld metal structure has a problem that the low-temperature toughness is lower than that of an austenite single-phase weld metal, and this problem becomes significant as the amount of ferrite increases (for example, non- Patent Document 2).

  On the other hand, when manufacturing hull structures, etc. that are used in a seawater environment and are required to ensure safety against aground on rocky reefs or collisions between ships, etc. Development of a high-corrosion-resistant stainless steel welding metallurgy welding wire that can form a weld metal that has excellent pitting corrosion resistance and crevice corrosion resistance and low temperature toughness is desired.

JP 58-205696 A JP-A-62-68696 Japanese Patent Laid-Open No. 1-95895 JP-A-3-86392 Onsawa et al .; Journal of the Japan Welding Society, vol.5 (1987), 262-268 D.T.Read et.al .; Welding Journal, vol.59 (1980), 104s-113

  In view of the above-mentioned problems of the prior art, the present invention is particularly suitable for the outer shell, bulkhead, aggregate, hydrofoil, etc. of a hull structure that requires durability, collision safety, etc. in a seawater environment. High corrosion resistance austenitic stainless steel welding wire that provides weld metal with excellent pitting corrosion resistance and crevice corrosion resistance in seawater environment and excellent low temperature toughness while maintaining weldability when assembled by welding The purpose is to provide.

  The present inventors conducted a gas shielded arc welding test using austenitic stainless steel solid wires and flux-cored wires having various component compositions, and maintained low weld toughness while maintaining low temperature toughness and corrosion resistance in a seawater environment. The component composition of the welding wire from which an excellent weld metal can be obtained was intensively studied.

  As a result, in order to reduce the ferrite phase harmful to low temperature toughness in the weld metal to such an extent that high temperature solidification cracking does not occur, the composition of the weld wire is changed to the austenite phase in the primary solidification phase of the weld metal formed by welding. Then, a solidification form in which solidification is completed in two phases of austenite phase + ferrite phase is obtained, and the Cr equivalent / Ni equivalent of the welding wire satisfies 1.0 to 1.2, and further in a seawater corrosive environment. In order to improve the pitting corrosion resistance of the weld metal, it has been found that it is an effective means to make the PI value of the welding wire 35 or more.

The present invention has been made on the basis of such knowledge, and the gist thereof is as follows.
(1) By mass%, C: 0.005 to 0.05%, Si: 0.1 to 1.0%, Mn: 0.1 to 2.5%, Cr: 25.0 to 28.0% , Ni: 16.0 to 23.9%, Mo: 1.6 to 3.0%, Cu: 0.1 to 0.5%, Al: 0.001 to 0.02%, N: 0.03 To 0.30%, further O: 0.03% or less, P: 0.03% or less, S: 0.005% or less, and defined by the following formulas (1) and (2) The ratio of Cr equivalent to Ni equivalent (Cr equivalent / Ni equivalent) is in the range of 1.0 to 1.2, the PI value defined by the following formula (3) is 35 or more, and the balance is iron and inevitable Solid wire for welding austenitic stainless steel with excellent low temperature toughness and seawater corrosion resistance, characterized by impurities.
Cr equivalent = [Cr] + [Mo] + 1.5 × [Si] (1)
Ni equivalent = [Ni] + 0.5 × [Mn] + 30 × [C] + 30 × [N] (2)
PI value = [Cr] + 3.3 × [Mo] + 16 × [N] (3)
However, said [Cr], [Mo], [Si], [Ni], [Mn], [C], [N] shows content (mass%) of each component in a welding wire.
(2) In the above-mentioned (%), further comprising one or two of Ti: 0.01 to 0.3% and Nb: 0.01 to 0.3% ( A solid wire for austenitic stainless steel welding excellent in low temperature toughness and seawater corrosion resistance as described in 1).
(3) The above-mentioned (%), further comprising one or two of Ca: 0.0005 to 0.0050% and Mg: 0.0005 to 0.0050% by mass% ( A solid wire for austenitic stainless steel welding excellent in low temperature toughness and seawater corrosion resistance as described in 1) or (2).
(4) In the outer skin or outer skin and flux, in mass% with respect to the total mass of the wire, C: 0.005 to 0.05%, Si: 0.1 to 1.0%, Mn: 0.1 to 2.5 %, Cr: 25.0 to 28.0%, Ni: 16.0 to 23.9%, Mo: 1.6 to 3.0%, Cu: 0.1 to 0.5%, Al: 0.0. 001 to 0.02%, N: 0.03 to 0.30%, P: 0.03% or less, S: 0.005% or less, and the following (1) and ( 2) The ratio of Cr equivalent to Ni equivalent defined by the formula (Cr equivalent / Ni equivalent) is in the range of 1.0 to 1.2, and the PI value defined by the following formula (3) is 35 or more. , The balance is made of iron and inevitable impurities, and is a flux-cored wire for welding austenitic stainless steel with excellent low-temperature toughness and seawater corrosion resistance. Ya.
Cr equivalent = [Cr] + [Mo] + 1.5 × [Si] (1)
Ni equivalent = [Ni] + 0.5 × [Mn] + 30 × [C] + 30 × [N] (2)
PI value = [Cr] + 3.3 × [Mo] + 16 × [N] (3)
However, said [Cr], [Mo], [Si], [Ni], [Mn], [C], [N] shows content (mass%) of each component in a welding wire.
(5) In the outer skin or the outer skin and the flux, in mass% with respect to the total mass of the wire, further, one of Ti: 0.01 to 0.3% and Nb: 0.01 to 0.3% Alternatively, the flux-cored wire for welding austenitic stainless steel having excellent low-temperature toughness and seawater corrosion resistance as described in (4) above, comprising two types.

  The present invention relates to a welding wire for high corrosion resistance austenitic stainless steel used in marine / gulf environments and chloride environments, and in particular, the outer shell, bulkhead, aggregate, hydrofoil, etc. of a hull structure are made of stainless steel. Welding for high-corrosion-resistant austenitic stainless steels that provides weld metal with excellent pitting corrosion resistance and crevice corrosion resistance in seawater environments and excellent low-temperature toughness while maintaining weldability A wire can be provided.

  Therefore, according to the present invention, it is possible to ensure the reliability of the stainless steel structure used in the marine / gulf environment and the chloride environment over a long period of time and improve the maintainability of the welded portion. The areas that contribute to the development of industries such as these fields are enormous.

  Hereinafter, the present invention will be described in detail.

  First, the technical idea for improving the low temperature toughness of the weld metal and the corrosion resistance in a seawater environment and the basic design of the welding wire component in the present invention will be described.

  According to the examination of the inventors' experiments and the like, when austenitic stainless steel is welded with a common metal welding wire, the solidification form of the weld metal changes depending on the wire component as follows, and the final It has been confirmed that this greatly affects the weld metal structure at room temperature and the low temperature toughness of the weld metal.

  In other words, the weld metal formed in the welded part is composed of a ferrite phase and a phase in which the primary solidification phase becomes an austenite phase or a ferrite phase depending on the component composition, and each of these phases completes solidification independently. The solidification form is classified into two phases of + austenite phase and solidification is completed.

  Among these, in the solidified form of the weld metal where the primary solidification phase of the weld metal is the ferrite phase, and then solidifies with the ferrite single phase as it is, the austenite phase is formed during the process of cooling the weld metal to room temperature. Although acicular precipitation occurs, finally, the ferrite phase in the weld metal at room temperature remains in a volume ratio of about 20% or more, and as a result, the low temperature toughness of the weld metal is significantly reduced.

  In the solidified form of the weld metal, where the primary solidification phase of the weld metal is the ferrite phase and then solidifies in two phases of ferrite phase + austenite phase due to crystallization of the austenite phase, the weld metal is then cooled to room temperature. In the process, the austenite phase grows into the ferrite phase which is a dendrite core, and finally the ferrite content in the weld metal at room temperature is reduced to about several to 20% by volume. However, the ferrite phase in the weld metal remains connected in a network, and when an impact load is applied, cracks propagate through the network-like ferrite phase, so that the low temperature toughness of the weld metal is lowered. In addition, the weld metal at room temperature has a toughness in the weld metal because Cr, Mo, etc. are concentrated in the ferrite phase, which is reduced in a network shape, and brittle intermetallic compounds such as the sigma phase are likely to precipitate. descend.

  On the other hand, the primary solidification phase of the weld metal is the austenite phase, and then the solidification form of the weld metal, which completes solidification in the two phases of austenite phase + ferrite phase due to crystallization of the ferrite phase, is then cooled to room temperature. In the metal structure, the spherical ferrite phase remains dispersed between austenite trees, and the ferrite content is reduced to several percent or less, so that the low-temperature toughness of the weld metal is less lowered than the above solidified form.

  Also, in the solidified form of the weld metal, where the primary crystal solidification phase of the weld metal is the austenite phase and then solidifies with the austenite single phase as it is, the low-temperature toughness of the weld metal is good. Since high temperature solidification cracking of metal is likely to occur, it is not preferable for maintaining good weldability.

  Based on the above findings, the present invention is based on the above knowledge, in order to reduce the ferrite phase harmful to low-temperature toughness in the weld metal to such an extent that solidification cracking does not occur, the component composition of the welding wire is the first of weld metals formed by welding. The technical idea is to realize a solidification form in which solidification is completed with the austenite phase being the austenite phase and then the two phases of the austenite phase and the ferrite phase.

  Further, as a result of detailed studies by the present inventors, the component system of the welding wire for realizing such technical idea and improving the low temperature toughness of the weld metal is organized using the following Cr equivalent and Ni equivalent indicators. I found that I can do it.

  FIG. 1 shows the relationship between the Cr equivalent and Ni equivalent of the welding wire and the solidification form of the weld metal.

Here, the Cr equivalent and the Ni equivalent of the welding wire are defined by the following equations (1) and (2). Cr equivalent is an index indicating the contribution of the welding wire component to the formation of the ferrite phase, and Ni equivalent is an index indicating the contribution of the welding wire component to the formation of the austenite phase.
Cr equivalent = [Cr] + [Mo] + 1.5 × [Si] (1)
Ni equivalent = [Ni] + 0.5 × [Mn] + 30 × [C] + 30 × [N] (2)
However, said [Cr], [Mo], [Si], [Ni], [Mn], [C], [N] shows content (mass%) of each component in a welding wire.

  From FIG. 1, when the Cr equivalent / Ni equivalent of the welding wire is 1.0 or more and 1.2 or less, the primary crystal solidification phase of the weld metal becomes an austenite phase, and then ferrite phase + austenite due to crystallization of the ferrite phase. Solidification is completed in two phases of solidification, reducing the amount of ferrite harmful to low temperature toughness in the weld metal at room temperature, and improving low temperature toughness (● in FIG. 1).

  On the other hand, if the Cr equivalent / Ni equivalent of the welding wire exceeds 1.2, the primary crystal solidification phase of the weld metal becomes a ferrite phase, and after that, solidification is completed with the ferrite single phase as it is, or crystallization of the austenite phase occurs. Even if solidification is completed in two phases of ferrite phase + austenite phase, the ferrite phase, which is harmful to the low temperature toughness in the weld metal at room temperature, contains many ferrite phases, so the intended low temperature toughness cannot be improved (in Fig. 1). ○).

  When the Cr equivalent / Ni equivalent is less than 1.0, the primary crystal solidification phase of the weld metal becomes an austenite phase, and then solidification is completed as it is with an austenite single phase. This solidification form of weld metal reduces the amount of ferrite harmful to the low temperature toughness in the weld metal at room temperature and improves the low temperature toughness of the weld metal. Not preferable (□ in FIG. 1).

  Therefore, in the present invention, in order to sufficiently reduce the low temperature toughness of the weld metal while reducing the ferrite phase harmful to the low temperature toughness in the weld metal to the extent that solidification cracking does not occur and maintaining the weldability, The ratio of the Cr equivalent to the Ni equivalent (Cr equivalent / Ni equivalent) of the welding wire defined in (1) and (2) above is satisfied within the range of 1.0 to 1.2. Stipulated.

  Further, from the examination of the present inventors and the like, when austenitic stainless steel is welded with a co-metal welding wire, the pitting corrosion resistance of the weld metal in a seawater corrosive environment is determined by the following (3 ) It was confirmed that the PI values defined by the formula are arranged.

FIG. 2 shows the relationship between the PI value of the welding wire and the pitting corrosion potential of the weld metal. The pitting corrosion potential is a potential measurement value when a pitting corrosion test is performed in a 3.5% NaCl solution at 40 ° C. and the current density is 100 mA / cm ² .
PI value = [Cr] + 3.3 × [Mo] + 16 × [N] (3)
However, said [Cr], [Mo], [N] shows each component content (mass%) in a welding wire.

  From FIG. 2, when the PI value defined by the above equation (3) of the welding wire is 35 or more, the pitting corrosion occurrence potential in the pitting corrosion test becomes 0.73 V or more, and pitting corrosion does not occur at all.

  Therefore, in the present invention, in order to sufficiently improve the pitting corrosion resistance of the weld metal in the seawater environment, the component composition of the welding wire is defined to satisfy the PI value defined in (3) above of 35 or more. did.

  Next, the reasons for limiting the component composition of the austenitic stainless steel welding wire and the austenitic stainless steel welding flux cored wire in the present invention will be described below.

  “%” Shown below means “% by mass” unless otherwise specified.

The welding wire of the present invention covers both solid wires and flux-cored wires. In the case of a flux-cored wire, the following components may be contained only in the outer skin, or may be contained in both the outer skin and the flux, and “%” in the outer skin or the outer skin and the flux indicates the outer skin relative to the total mass of the wire. Or the mass% of the component content contained in an outer_layer | skin and a flux is meant. In addition, content (mass%) of each component with respect to the wire total mass in a flux-cored wire: Mw is defined by the following (4) formula.
Mw = (1-R) × Mc + R × Mf (4)
Where, Mc: content (% by mass) of each component in the wire sheath, Mf: content (% by mass) of each component in the flux, and R: ratio (% by mass) of the flux to the total mass of the wire. .

  C: C is harmful to corrosion resistance, but it needs to be contained to some extent from the viewpoint of strength, so 0.005% or more is added. Further, if the content exceeds 0.05%, when it is in a welded state and reheated, C combines with Cr to precipitate Cr carbide, and the intergranular corrosion resistance and pitting corrosion resistance are remarkably deteriorated. The toughness and ductility of the weld metal are remarkably lowered, so the content is limited to 0.005 to 0.05%.

  Si: Si is added as a deoxidizing element and an element that suppresses the surface tension of droplets. However, if the content is less than 0.1%, the effect is not sufficient. On the other hand, if the content exceeds 1.0%, the ductility decreases. Along with this, the toughness is greatly reduced and the melt penetration during welding is reduced, which becomes a problem in practical welding. Therefore, the content is limited to 0.1 to 1.0%.

  Mn: Mn is added as a deoxidizing element, but if its content is less than 0.1%, the effect is not sufficient. On the other hand, if it exceeds 2.5%, the ductility is lowered, so its content is reduced to 0. Limited to 1-2.5%.

  Cr: Cr forms a passive film as a main element of austenitic stainless steel and contributes to improvement of corrosion resistance. In the case of containing Ni, Mo, Cu, N, it is 25.0 to obtain solidification by primary austenite phase solidification, solidification in two phases of austenite phase + ferrite phase, and excellent corrosion resistance in a seawater environment. % Or more is necessary. On the other hand, the greater the Cr content, the better the pitting corrosion resistance in a seawater environment, but the brittle intermetallic compounds such as the sigma phase are likely to precipitate, resulting in a decrease in toughness. In addition, since Cr is a ferrite-forming element, it is necessary to increase the amount of Ni, Cu, and N in order to solidify in the primary austenite phase, which decreases the wire manufacturability and increases the manufacturing cost. The upper limit of 28.0%.

  Ni: Ni provides remarkable resistance to corrosion in a neutral chloride environment and strengthens the passive film, so that the higher the Ni content, the more effective the corrosion resistance. Ni is an austenite-forming element, and as a main element of austenitic stainless steel, austenite phase is generated and stabilized. In the present invention, it is necessary to make a component system that solidifies in the primary austenite phase and completes solidification in the two phases of the austenite phase and the ferrite phase, so that Cr, which is a ferrite forming element, is 25.0 to 28.0. From the viewpoint of the solidification form and the phase balance when added in an amount of 1%, the Ni content was set to 16.0% to 23.9%. The upper limit of 23.9% of the Ni content is limited because the production cost is increased, although the decrease in wire productivity such as Cr is small.

  Mo: Mo is an element that is extremely effective in stabilizing the passive film and obtaining high corrosion resistance. In particular, the pitting corrosion resistance is significantly improved in a chloride environment, but if it is less than 1.6%, the effect is insufficient. Further, if the content exceeds 3.0%, brittle intermetallic compounds such as a sigma phase are generated and the toughness of the weld metal is lowered, so the content is limited to 1.6 to 3.0%.

  Cu: Cu has a remarkable effect in increasing strength and corrosion resistance. Particularly, it coexists with Ni and Mo and exhibits excellent corrosion resistance in a neutral acid environment. The effect is remarkable at 0.1% or more. Even if added over 5%, the effect is saturated and the toughness is lowered, so the Cu content is made 0.1 to 0.5%.

  Al: Al is added as a deoxidizing element and an element that improves the droplet transfer phenomenon, but if less than 0.001%, the effect is not sufficient, while excessive addition reacts with N. AlN is formed to inhibit toughness. The degree depends on the N content, but when Al exceeds 0.02%, the toughness deteriorates remarkably, so the content is limited to 0.001 to 0.02%.

  N: N is a strong austenite-forming element and improves pitting corrosion resistance in a chloride environment. When the content is 0.03% or more, the pitting corrosion resistance and crevice corrosion resistance are improved. The greater the content, the greater the effect. On the other hand, when the N content is increased, in order to complete solidification in the two phases of austenite phase + ferrite phase, it is necessary to increase the amount of ferrite-forming elements such as Cr and Mo, which increases the manufacturing cost. Furthermore, if it exceeds 0.30%, blow holes are likely to occur during welding. Therefore, the N content is limited to 0.03 to 0.30%.

  O, P, and S are inevitable components in the weld metal and are limited to a small amount for the following reasons.

  O: O generates an oxide, and excessive content significantly reduces toughness. Therefore, the upper limit of the content was set to 0.03%. The flux-cored wire contains various oxides in the flux, oxygen exists as a compound, and it is difficult to limit the amount of oxygen, so the amount of oxygen is limited only for the solid wire.

  P: When P is present in a large amount, the high temperature weld cracking resistance and toughness during solidification are deteriorated, so it is desirable that the content be less. The upper limit of the content is 0.03%.

  S: If S is also present in a large amount, the hot cracking resistance, ductility and corrosion resistance are deteriorated, so a smaller amount is desirable, and 0.005% was made the upper limit.

  Although the above is a basic component of the welding wire of the present invention, the following components can be selectively added.

  Ti: Ti combines with C to suppress the precipitation of Cr carbide, and has the effect of improving the corrosion resistance of the weld metal. In order to obtain the effect, addition of 0.01% or more is effective. However, addition of more than 0.3% lowers the ductility and toughness. 3%.

  Nb: Nb also has an action of combining with C to suppress the precipitation of Cr carbide and improve the corrosion resistance of the weld metal. In order to obtain the effect, addition of 0.01% or more is effective. However, addition of more than 0.3% lowers the ductility and toughness. 3%.

  Ca: Ca is an element that improves hot workability and improves wire manufacturability. However, excessive addition conversely reduces hot workability, so when added, the content is made 0.0005 to 0.0050%.

  Mg: Mg is also an element that improves hot workability and improves wire manufacturability. However, excessive addition conversely reduces hot workability, so when added, the content is made 0.0005 to 0.0050%.

  In the present invention, as an austenitic stainless steel welding wire, the austenitic stainless steel is welded by using a solid wire or a flux-cored wire with the specified component content as described above, thereby providing excellent low-temperature toughness and seawater environment. A weld metal having corrosion resistance is obtained.

  The austenitic stainless steel welding wire of the present invention is used as a welding method for TIG welding, MIG welding, plasma welding, laser welding, submerged arc welding, as well as the core wire or flux of a coated arc welding rod. It can also be used as the outer skin of a cored wire. Furthermore, the welding wire can be applied to the manufacture of welded structures and also to repair welding or overlaying of the structures.

  Hereinafter, the present invention will be described with reference to examples.

Table 1 shows the composition of the produced solid wire for welding. The wire diameter is 1.2 mmφ. Further, the balance of the composition shown in Table 1 is iron and inevitable impurities, and the solidification mode is A in which solidification is completed in a single austenite phase and AF in which solidification is completed in two phases of primary austenite + ferrite. FA indicates a solid phase in which the solidification is completed in two phases of primary ferrite + austenite. Next, on the SUS304 stainless steel plate having a thickness of 10 mm, using the above-mentioned solid wire for welding, welding current: 150 to 200 A, arc voltage: 23 to 31 V, welding speed: 30 to 40 cm / min, 98% Ar + 2% Overlay welding of 10 layers was performed by a gas shield welding method with an O ₂ shield gas flow rate of 20 liters / min.

Furthermore, a flux-cored wire having a wire diameter of 1.2 mmφ having the composition shown in Table 2 as mass% with respect to the total mass of the wire was produced. The balance of the composition shown in Table 2 is also iron and unavoidable impurities, and the solidification mode is A in which solidification is completed in an austenite single phase, and AF in which solidification is completed in two phases of primary austenite + ferrite. FA indicates a solid phase in which the solidification is completed in two phases of primary ferrite + austenite. Next, on the SUS304 stainless steel plate having a thickness of 10 mm, using the above-mentioned flux-cored wire, welding current: 150 to 200 A, arc voltage: 23 to 31 V, welding speed: 30 to 40 cm / min, 100% CO ₂ shield 10 layers of overlay welding were performed at a gas flow rate of 20 liters / min.

  V-notch specimens defined in JIS Z 2202 were collected from each build-up weld metal, and a Charpy impact test was performed at a test temperature of −40 ° C. Also, pitting corrosion test specimens were collected from the surface layer of each build-up weld metal, and pitting corrosion potential was measured in a 3.5% NaCl solution at 40 ° C in accordance with the method specified in JIS G 0577. did.

Table 3 shows the Charpy impact test results and pitting corrosion test results when using a solid wire, and Table 4 shows the Charpy impact test results and pitting corrosion test results when using a flux-cored wire. The pitting corrosion potential in Tables 3 and 4 indicates the potential at a current density of 100 mA / cm ^2. The pitting corrosion potential indicates that no pitting corrosion occurred and oxygen was generated by electrolysis of water. Is shown.

  In Tables 3 and 4, the comparative examples of the symbols k and I have pitting corrosion because C and Cr are out of the range and the PI value is low. Symbol 1 and Symbol J have a low Ni content, and Symbol m and Symbol K have a Cr equivalent / Ni equivalent ratio exceeding 1.2 because Cr and Mo are more than the specified range, and the primary ferrite phase Solidification occurs, and the Charpy impact value is significantly reduced. Since the symbol n and the symbol L have a low N content and a low PI value, pitting corrosion has occurred. The symbols o and M are within the range for each element, but pitting corrosion occurs because the PI value is low. In addition, each of the symbols p and N is within the range, but since the Cr equivalent / Ni equivalent ratio exceeds 1.2 and the primary ferrite phase solidifies, the Charpy impact value becomes low. Yes. Symbol q and symbol O are good in both Charpy impact value and pitting corrosion resistance, but the Cr equivalent / Ni equivalent ratio is less than 1.0, resulting in austenite single phase solidification and solidification cracks occurring during welding. Yes.

  On the other hand, the examples of the present invention of symbols a to j and symbols A to H have a higher Charpy impact value and pitting corrosion than the comparative examples because the component content and the relationship between the components are within the scope of the present invention. Neither has occurred. In addition, the Charpy impact value of the weld metal by the flux cored wires of symbols A to H is lower than the Charpy impact value of the weld metal by the solid wires of symbols a to j due to the difference in the amount of oxide in the weld metal. is there.

It is a figure which shows the relationship between Cr equivalent of a weld metal, Ni equivalent, and its solidification form. It is a figure which shows the relationship between PI value (= Cr + 3.3xMo + 16xN) of a weld metal, and the pitting corrosion potential in a 3.5% NaCl solution of 40 degreeC.

Claims (5)

In mass%, C: 0.005 to 0.05%, Si: 0.1 to 1.0%, Mn: 0.1 to 2.5%, Cr: 25.0 to 28.0%, Ni: 16.0-23.9%, Mo: 1.6-3.0%, Cu: 0.1-0.5%, Al: 0.001-0.02%, N: 0.03-0. Contains 30%,
Furthermore, it is limited to O: 0.03% or less, P: 0.03% or less, S: 0.005% or less,
And the ratio (Cr equivalent / Ni equivalent) of Cr equivalent and Ni equivalent defined by the following formulas (1) and (2) is in the range of 1.0 to 1.2, and is defined by the following formula (3). A solid wire for austenitic stainless steel welding excellent in low temperature toughness and seawater corrosion resistance, characterized by having a PI value of 35 or more and the balance being iron and inevitable impurities.
Cr equivalent = [Cr] + [Mo] + 1.5 × [Si] (1)
Ni equivalent = [Ni] + 0.5 × [Mn] + 30 × [C] + 30 × [N] (2)
PI value = [Cr] + 3.3 × [Mo] + 16 × [N] (3)
However, said [Cr], [Mo], [Si], [Ni], [Mn], [C], [N] shows content (mass%) of each component in a welding wire.   2. The composition according to claim 1, further comprising at least one of Ti: 0.01 to 0.3% and Nb: 0.01 to 0.3% by mass%. Solid wire for welding austenitic stainless steel with excellent low temperature toughness and seawater corrosion resistance.   The composition further comprises one or two of Ca: 0.0005 to 0.0050% and Mg: 0.0005 to 0.0050% by mass%. Item 3. A solid wire for welding austenitic stainless steel excellent in low-temperature toughness and seawater corrosion resistance according to Item 2. In the outer sheath or outer sheath and flux, in mass% with respect to the total mass of the wire, C: 0.005 to 0.05%, Si: 0.1 to 1.0%, Mn: 0.1 to 2.5%, Cr : 25.0 to 28.0%, Ni: 16.0 to 23.9%, Mo: 1.6 to 3.0%, Cu: 0.1 to 0.5%, Al: 0.001 to 0 0.02%, N: 0.03 to 0.30%,
Furthermore, it is limited to P: 0.03% or less, S: 0.005% or less,
And the ratio (Cr equivalent / Ni equivalent) of Cr equivalent and Ni equivalent defined by the following formulas (1) and (2) is in the range of 1.0 to 1.2, and is defined by the following formula (3). A flux cored wire for austenitic stainless steel welding excellent in low temperature toughness and seawater corrosion resistance, characterized by having a PI value of 35 or more and the balance being iron and inevitable impurities.
Cr equivalent = [Cr] + [Mo] + 1.5 × [Si] (1)
Ni equivalent = [Ni] + 0.5 × [Mn] + 30 × [C] + 30 × [N] (2)
PI value = [Cr] + 3.3 × [Mo] + 16 × [N] (3)
However, said [Cr], [Mo], [Si], [Ni], [Mn], [C], [N] shows content (mass%) of each component in a welding wire.   In the outer skin or the outer skin and the flux, in mass% with respect to the total mass of the wire, further, one or two of Ti: 0.01 to 0.3% and Nb: 0.01 to 0.3% The flux-cored wire for austenitic stainless steel welding excellent in low-temperature toughness and seawater corrosion resistance according to claim 4.

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