JP5088245B2 - Stainless steel welded joint weld metal - Google Patents

Description

The present invention, chemical plants, building materials, water heaters, tanks, household appliances, automobile parts, Ru Oh those about the weld metals formed welded joints available stainless steel in a wide range of fields such as kitchen equipment.

  Generally, stainless steels that are widely used are roughly classified into austenitic stainless steel (for example, SUS304) and ferritic stainless steel (for example, SUS430). SUS304, an austenitic stainless steel, is a stainless steel with about 18% Cr and 8% Ni added to Fe, and SUS430, a ferritic stainless steel, contains about 17% Cr by weight. Added stainless steel.

When comparing the corrosion resistance of SUS430 and SUS304, austenitic stainless steel (ie, SUS304) is superior. However, with the advancement of refining technology, a technology for reducing C in molten steel has been established, and it has become possible to improve the corrosion resistance of ferritic stainless steel.
In other words, ferritic stainless steel and austenitic stainless steel manufactured using technology developed in recent years are all excellent in corrosion resistance, such as chemical plants, building materials, water heaters, tanks, home appliances, automobile parts, kitchen equipment. It is used in various fields such as.

  When producing a product having a predetermined shape using a stainless steel plate, it is necessary to join a plurality of stainless steel plates. As a joining technique, arc welding (for example, TIG welding, MIG welding, MAG welding, etc.) is widely adopted. Welding materials used in arc welding are welding materials such as 308 series and 308L series (for example, D308, D308L, Y308, Y308L, etc.) used in arc welding of austenitic stainless steel sheets. In arc welding, a welding material such as 309L (for example, D309L, Y309L, etc.) is used. If these welding materials are used, the effect of ensuring the corrosion resistance of the weld metal formed in the weld joint can be obtained.

  When producing products made of stainless steel sheets, welding between ferritic stainless steel sheets or austenitic stainless steel sheets is generally used from the viewpoint of improving the efficiency of welding work and ensuring the soundness of the weld metal (for example, patent documents). 1). However, some products made of stainless steel plates require different characteristics depending on each part. In order to produce a product using a material suitable for each part, it may be necessary to weld a ferritic stainless steel plate and an austenitic stainless steel plate.

As already explained, both ferritic stainless steel sheets and austenitic stainless steel sheets manufactured in recent years are excellent in corrosion resistance. However, a weld metal formed by welding a ferritic stainless steel plate and an austenitic stainless steel plate has a problem of poor corrosion resistance.
Japanese Patent No. 3190290

The present invention relates to welded joints between ferritic stainless steel sheet and austenite stainless steel sheet, and an object that you provide a weld metal having excellent corrosion resistance.

  In order to achieve the above-mentioned problems, the inventors diligently studied the influence of the components and the structure on the corrosion resistance of the weld metal formed on the welded joint between the ferritic stainless steel plate and the austenitic stainless steel plate. As a result, it was found that the corrosion resistance of the weld metal can be improved by controlling the components of the weld metal. Furthermore, the knowledge that the corrosion resistance of the weld metal can be further improved by controlling the structure of the weld metal was obtained.

The present invention has been made based on these findings.
That is, the present invention is a weld metal of a stainless steel welded joint formed by welding a ferritic stainless steel plate and an austenitic stainless steel plate, Cr: 18 to 21% by mass, Mo: 0.1% by mass or less, Cu: 0.5% by mass or less, Ti: 0.03 to 0.2% by mass, Nb: 0.025% by mass or less, N: 0.04% by mass or less, and Cr equivalent calculated by the following formula (1) within the range of 18-25 It contains Cr, Mo, Si, Nb, Ni, C and Mn so that the Ni equivalent calculated by the following formula (2) satisfies the range of 3 to 17, and the fraction of austenite phase Is a weld metal of a stainless steel welded joint having a structure in which the C content of the austenite phase is 0.04% by mass or less.

Cr equivalent = [% Cr] + [% Mo] + 1.5 [% Si] + 0.5 [% Nb] (1)
Ni equivalent = [% Ni] + 30 [% C] + 0.5 [% Mn] (2)
[% Cr]: Cr content of weld metal (mass%)
[% Mo]: Mo content of weld metal (mass%)
[% Si]: Weld metal Si content (mass%)
[% Nb]: Nb content of weld metal (% by mass)
[% Ni]: Ni content (mass%) of weld metal
[% C]: C content (mass%) of the weld metal
[% Mn]: Mn content (mass%) of weld metal
In order to form the weld metal of the present invention, the ferritic stainless steel sheet contains C: 0.030 mass% or less, N: 0.030 mass% or less, and the total content of C and N is 0.050 mass% or less, And Si: 0.40 mass% or less, Mn: 0.50 mass% or less, P: 0.040 mass% or less, S: 0.010 mass% or less, Cr: 20.5-22.5 mass%, Cu: 0.03-1.00 mass%, Ni: 0.8 mass% In the following, Al: 0.10% by mass or less, Nb: 0.10 to 1.00% by mass, and Ti: 0.10 to 1.00% selected from one or two types, with the balance being Fe and inevitable impurities It is preferable. Furthermore, it is preferable that a ferritic stainless steel plate contains 1 type (s) or 2 or more types chosen from V: 0.01-0.5 mass%, W: 0.01-5 mass%, and B: 0.0002-0.0030 mass%.

  ADVANTAGE OF THE INVENTION According to this invention, the corrosion resistance of the weld metal formed in the welded joint of the different steel types of a ferritic stainless steel plate and an austenitic stainless steel plate can be improved.

First, the components of the weld metal obtained by applying the present invention will be described.
Cr equivalent: 18-25, Ni equivalent: 3-17
Cr equivalent is a value calculated by the following equation (1) using a ferrite stabilizing element, and Ni equivalent is a value calculated by the following equation (2) using an austenite stabilizing element.
Cr equivalent = [% Cr] + [% Mo] + 1.5 [% Si] + 0.5 [% Nb] (1)
Ni equivalent = [% Ni] + 30 [% C] + 0.5 [% Mn] (2)
[% Cr]: Cr content of weld metal (mass%)
[% Mo]: Mo content of weld metal (mass%)
[% Si]: Weld metal Si content (mass%)
[% Nb]: Nb content of weld metal (% by mass)
[% Ni]: Ni content (mass%) of weld metal
[% C]: C content (mass%) of the weld metal
[% Mn]: Mn content (mass%) of weld metal
In order to make the weld metal a two-phase structure of austenite and ferrite, the Cr equivalent is in the range of 18 to 25 and the Ni equivalent is in the range of 3 to 17. Therefore, Cr, Mo, Si, Nb, Ni, C, and Mn contained in the weld metal are adjusted so that the Cr equivalent and the Ni equivalent satisfy the predetermined range. For example, the content of Cr, Mo, Si, Nb, Ni, C, and Mn of the weld metal is adjusted by a method such as selecting and welding a stainless steel plate or a stainless welding wire having a suitable component.

Cr: 18-21% by mass
Cr is an indispensable element for improving the corrosion resistance of the weld metal, and is supplied to the weld metal from a stainless steel plate or welding wire used for welding. However, if the Cr content is less than 18% by mass, the effect of improving the corrosion resistance of the weld metal cannot be obtained. On the other hand, when it exceeds 21% by mass, the toughness of the stainless steel sheet is lowered. Therefore, Cr is in the range of 18 to 21% by mass.

Mo: 0.1% by mass or less
Mo is an element that improves the corrosion resistance of the weld metal, and is supplied to the weld metal from a stainless steel plate or welding wire used for welding. However, since Mo is expensive, if it is contained excessively, the manufacturing cost of a stainless steel plate (or the manufacturing cost of a product manufactured by welding a stainless steel plate) is increased. Therefore, Mo is 0.1% by mass or less. Even if Mo is contained to the extent of inevitable impurities, it is effective. Therefore, Mo is preferably in the range of 0.001 to 0.1% by mass.

Cu: 0.5% by mass or less
Cu, like Mo, is an element that improves the corrosion resistance of the weld metal, and is supplied to the weld metal from a stainless steel plate or welding wire used for welding. However, when Cu is contained excessively, the hot workability of the stainless steel plate is lowered. Therefore, Cu is 0.5 mass% or less. Cu is effective even if it is contained to the extent of inevitable impurities. Therefore, Cu is preferably within the range of 0.001 to 0.5 mass%.

Ti: 0.03-0.2 mass%
Ti is an element that preferentially forms carbonitride, and has the effect of preventing intergranular corrosion by preventing Cr in the weld metal from combining with C and N during welding of a stainless steel plate. If the Ti content is less than 0.03% by mass, the effect cannot be obtained. On the other hand, when it exceeds 0.2 mass%, the production | generation of austenite will be inhibited. Therefore, Ti is in the range of 0.03-0.2 mass%.

Nb: 0.025 mass% or less
Like Ti, Nb is an element that preferentially forms carbonitrides, and prevents Cr in the weld metal from combining with C and N during the welding of stainless steel plates, and suppresses intergranular corrosion. Have However, if the Nb content exceeds 0.025 mass%, hot cracking is likely to occur during welding. Accordingly, Nb is set to 0.025 mass% or less. Nb is effective even if it is contained to the extent of inevitable impurities. Therefore, Nb is preferably in the range of 0.001 to 0.025 mass%.

N: 0.04 mass% or less N is an element that combines with Cr to form Cr nitride. If Cr nitride precipitates on the weld metal, the effect of Cr that improves the corrosion resistance of the weld metal cannot be obtained. If the N content exceeds 0.04% by mass, Cr nitride tends to precipitate on the weld metal. Therefore, N is set to 0.04 mass% or less. However, if the N content is less than 0.0050% by mass, the amount of austenite phase generated in the weld metal is reduced. Therefore, N is preferably in the range of 0.0050 to 0.04 mass%.

The components of the weld metal described above are basic components, and other elements can be appropriately contained in the present invention. For example, P, S, Al, Cu, Ni, V, W, B, Ca, etc.
Next, the structure of the weld metal obtained by applying the present invention will be described.
Austenite phase fraction: 20% or more The weld metal has a two-phase structure of austenite and ferrite. However, depending on the components of the stainless steel and welding wire used for welding or the welding conditions, a part of austenite becomes martensite. When the austenite phase fraction is less than 20%, it is difficult to impart corrosion resistance to the weld metal. Therefore, the fraction of the austenite phase is 20% or more. However, if the austenite phase fraction exceeds 80%, the corrosion resistance of the weld metal is improved, but it is difficult to obtain an austenite phase fraction exceeding 80% by a general welding method. Therefore, the fraction of the austenite phase is preferably in the range of 20 to 80%. The above-described values can be obtained by a method for obtaining the austenite phase fraction by observing the structure of the weld metal or a method for obtaining the austenite phase fraction from the weld metal components based on the Schaeffler phase diagram.

C content of austenite phase: 0.04% by mass or less C is an element that forms Cr carbide by combining with Cr. When Cr carbide precipitates on the weld metal, the effect of Cr that improves the corrosion resistance of the weld metal cannot be obtained. When the C content of the austenite phase exceeds 0.04% by mass, Cr carbide tends to precipitate on the weld metal. Therefore, C is 0.04 mass% or less. However, if the C content of the austenite phase is less than 0.005% by mass, the amount of austenite phase generated in the weld metal is reduced. Therefore, C is preferably in the range of 0.005 to 0.04 mass%. The C content of the austenite phase is a value obtained by dividing the C content of the weld metal by the fraction of the austenite phase (including the martensite phase) of the weld metal.

The components of a stainless steel plate suitable for forming a weld metal having the composition and structure described above will be described below.
C: 0.030 mass% or less, N: 0.030 mass% or less, C and N: total 0.050 mass% or less C and N combine with Cr during welding to form Cr carbide and Cr nitride. When Cr carbide or Cr nitride precipitates on the weld metal, a Cr-deficient layer is formed and promotes intergranular corrosion. Therefore, the less C and N, the more the intergranular corrosion of the weld metal can be suppressed. For these reasons, the C content is 0.030 mass% or less, the N content is 0.030 mass% or less, and the total content of C and N is 0.050 mass% or less. Preferably, the C content is 0.015 mass% or less, the N content is 0.015 mass% or less, and the total content of C and N is 0.030 mass% or less. However, if the C content is less than 0.0050% by mass, the amount of austenite phase generated in the weld metal is reduced. Therefore, C is preferably in the range of 0.0050 to 0.030 mass%. On the other hand, if the N content is less than 0.0050% by mass, the amount of austenite phase produced in the molten metal is reduced. Therefore, N is preferably in the range of 0.0050 to 0.030 mass%. The total content of C and N is preferably in the range of 0.0050 to 0.030 mass%.

Si: 0.40 mass% or less
Si is an element that increases the strength of the weld metal, and decreases the workability and toughness as the strength increases. Therefore, it is desirable to reduce Si as much as possible, but it also has the effect of improving the oxidation resistance of the weld metal. For this reason, the Si content is set to 0.40% by mass or less. Preferably it is 0.20 mass% or less. However, when the Si content is less than 0.01% by mass, it is difficult to ensure the strength. Therefore, Si is more preferably in the range of 0.01 to 0.40 mass%. A range of 0.05 to 0.20% by mass is more preferable.

Mn: 0.50 mass% or less
Mn combines with S during welding to form MnS. This MnS is a soluble sulfide and adversely affects the corrosion resistance of the weld metal. For this reason, the Mn content is set to 0.50% by mass or less. Preferably it is 0.30 mass% or less. However, if the Mn content is less than 0.01% by mass, it is difficult to ensure the strength. Therefore, Mn is more preferably in the range of 0.01 to 0.50 mass%. A range of 0.05 to 0.30% by mass is more preferable.

P: 0.040% by mass or less P is an element harmful to hot workability and corrosion resistance. In particular, when P of the stainless steel plate exceeds 0.040% by mass, the corrosion resistance of the weld metal is remarkably lowered. Therefore, P is set to 0.040 mass% or less. However, P may be contained to the extent of inevitable impurities.
S: 0.010% by mass or less S is an element harmful to hot workability and corrosion resistance. In particular, when the S content of the stainless steel plate exceeds 0.010% by mass, the corrosion resistance of the weld metal is significantly reduced. Therefore, S is 0.010 mass% or less. Preferably it is 0.005 mass% or less. However, S may be contained to the extent of inevitable impurities.

Cr: 20.5-22.5 mass%
Cr is an element that improves corrosion resistance, and is an indispensable element particularly in ferritic stainless steel sheets. In order to obtain corrosion resistance corresponding to SUS304, it is necessary to contain 20.5% by mass or more of Cr. On the other hand, when it exceeds 22.5% by mass, the toughness of the stainless steel sheet is remarkably lowered, which hinders its production. Therefore, Cr is in the range of 20.5 to 22.5 mass%.

Cu: 0.03-1.00 mass%
Cu is an element that improves corrosion resistance. If the Cu content is less than 0.03% by mass, the effect of improving the corrosion resistance of the weld metal cannot be obtained. On the other hand, if it exceeds 1.00% by mass, the hot workability deteriorates, which hinders the production of stainless steel sheets. Therefore, Cu shall be in the range of 0.03-1.00 mass%. Preferably it is 0.40-0.70 mass%.

Ni: 0.8% by mass or less
Ni is an element that improves corrosion resistance. It also has an effect of suppressing deterioration of hot workability due to Cu. However, since Ni is expensive, it is set to 0.8% by mass or less from the viewpoint of reducing the manufacturing cost of the stainless steel plate. Ni is effective even if it is contained to the extent of inevitable impurities. Therefore, Ni is preferably within the range of 0.001 to 0.8 mass%.

Al: 0.10 mass% or less
Al is an element that acts as a deoxidizer for weld metal during welding and contributes to reduction of solid solution N by combining with N. If the Al content exceeds 0.10 mass%, further improvement of the deoxidation effect and the solid solution N reduction effect cannot be expected. Therefore, Al is 0.10 mass% or less. However, if the Al content is less than 0.005% by mass, the deoxidation effect cannot be obtained. Therefore, Al is preferably within a range of 0.005 to 0.10% by mass.

One or two selected from Nb: 0.10 to 1.00% by mass and Ti: 0.10 to 1.00% by mass
Nb and Ti both form carbonitrides during welding to reduce solute C and solute N, thereby suppressing the formation of Cr carbonitrides and improving the ductility, toughness and corrosion resistance of weld metals. Has an effect. Nb also has the effect of improving the high temperature strength of the weld metal. If Nb and Ti are both less than 0.10% by mass, these effects cannot be obtained. On the other hand, if the content exceeds 1.00% by mass, the ductility of the weld metal decreases. Therefore, Nb: 0.10 to 1.00% by mass, Ti: 0.10 to 1.00% by mass. Preferably, they are Nb: 0.30-0.50 mass%, Ti: 0.15-0.45 mass%. One of Nb and Ti may be added, or both may be used in combination.

In addition to the above-described components, the stainless steel plate to which the present invention is applied may contain the following components as necessary.
V: 0.01 to 0.5 mass%, W: 0.01 to 5 mass%, B: One or more selected from 0.0002 to 0.0030 mass% V and W are both weld cracking susceptibility in the heat affected zone. Has the effect of improving. Nb also has the effect of improving the high temperature strength of the weld metal. These effects cannot be obtained if the contents of V and W are too small. On the other hand, if the content is excessive, the toughness of the weld heat affected zone decreases. Therefore, V: 0.01 to 0.5 mass%, W: 0.01 to 5 mass%. Preferably, V: 0.05 to 0.3% by mass and W: 0.1 to 3% by mass. One of V and W may be added, or both may be used in combination.

B: 0.0002 to 0.0030 mass%
B is an element that improves hardenability and has the effect of improving the toughness of the weld heat affected zone. If the B content is less than 0.0002% by mass, the effect cannot be obtained. On the other hand, if it exceeds 0.0030% by mass, the strength of the heat affected zone is excessively increased, and the toughness and workability are impaired. Therefore, B is in the range of 0.0002 to 0.0030 mass%. Preferably it is 0.0005-0.0010 mass%.

The balance other than the above components is Fe and inevitable impurities. Inevitable impurities are inevitably mixed in the stage of melting or rolling stainless steel. Inevitable impurities include, for example, O, Mg, Ca and the like. These elements can accept O: 0.015 mass% or less, Mg: 0.0020 mass% or less, Ca: 0.0020 mass% or less.
The procedure for manufacturing the stainless steel plate described above will be described below.

Primary refining is performed in converters, electric furnaces, vacuum melting furnaces, etc., followed by secondary refining by strong stirring vacuum oxygen decarburization (so-called VOD) method, argon oxygen decarburization (so-called AOD) method, etc. Molten steel having the following components is produced. The obtained molten steel is subjected to continuous casting or ingot making into a slab.
The slab is heated to 1100-1250 ° C. and hot-rolled to form a hot-rolled coil (thickness of about 2.0-6.0 mm), further annealed at 800-1100 ° C., and then pickled. When the annealing temperature is less than 800 ° C., strain generated by hot rolling remains, the hot-rolled coil becomes hard, and wrinkles are easily generated on the surface. On the other hand, when it exceeds 1100 ° C., the toughness of the hot-rolled coil decreases due to coarsening. In addition, a hot-rolled coil refers to what wound up the hot-rolled steel plate.

  The hot-rolled coil that has been pickled is cold-rolled and further subjected to finish annealing and pickling to obtain a cold-rolled coil (thickness of about 0.03 to 5.00 mm). The rolling reduction of cold rolling is preferably 25% or more in order to maintain good mechanical properties such as toughness and workability. More preferably, it is 50% or more. Further, the steps from cold rolling to pickling may be repeated. Bright annealing may be performed as the final annealing. In addition, a cold-rolled coil refers to what wound up the cold-rolled steel plate.

  When welding the stainless steel plate by applying the present invention, it is preferable to use the ferritic stainless steel plate described above in combination with another austenitic stainless steel. The welding method is preferably TIG welding, MIG welding, MAG welding, or the like, which is performed using a welding material (for example, a welding wire, filler metal, etc.) in an inert gas atmosphere. However, if the cooling rate in the temperature range from 1000 ° C to 600 ° C where the carbide precipitates on the weld metal obtained by welding is less than 10 ° C / second, a large amount of Cr carbide precipitates and the corrosion resistance of the weld metal is significantly reduced. To do. Therefore, cooling is performed at a cooling rate of 10 ° C./second or more in a range from 1000 ° C. to 600 ° C.

<Example 1>
Stainless steel having the component of steel symbol A shown in Table 1 was melted in a small vacuum melting furnace to form a 100 kg steel ingot. The obtained steel ingot was heated to 1100 ° C. and hot-rolled under conditions of a finishing temperature of 750 ° C. and a winding temperature of 650 ° C. to obtain a hot-rolled steel sheet having a thickness of 4.0 mm. The hot-rolled steel sheet was annealed at 800 ° C., pickled, and cold-rolled to obtain a cold-rolled steel sheet having a thickness of 1.5 mm. Subsequently, the cold-rolled steel sheet was subjected to finish annealing at 900 ° C., and further cooled and pickled.

The cold-rolled steel sheet was combined with a stainless steel sheet (SUS304 equivalent, thickness 3.5 mm) having the component of steel symbol a shown in Table 2 and butt-welded by MIG welding to produce a welded joint. The groove shape was an I groove, and the dilution ratio of the steel sheet was changed by variously adjusting the gap. The conditions for MIG welding are as follows.
Welding voltage: 18-20V
Welding current: 90-110A
Welding speed: 600 to 800 mm / min Shielding gas component: Ar-2 vol% O ₂
Shielding gas flow rate: 15 liter / min Welding wire: Y308, Y308L, Y309, Y309L
Wire diameter: 1.2mm

  Centering on the weld bead of the obtained welded joint, a test piece with a width of 60 mm and a length of 80 mm is collected, and after removing the weld bead by machining, it is polished with # 600 abrasive paper, The temper collar by welding was removed. Next, in order to investigate the corrosion resistance of the welded joint, a combined cycle corrosion test was conducted. In the combined cycle corrosion test, salt spray (35 ° C., 2 hours, 5 mass% NaCl) → drying (60 ° C., 4 hours) → wet (50 ° C., 2 hours) was repeated for 30 cycles.

After the combined cycle corrosion test was completed, the appearance of the weld metal was visually observed to investigate the rusting situation. The rusting status was evaluated as A for no red rust, B for red rust area less than 10%, C for red rust area 10% to less than 30%, D for red rust area 30% to less than 70%, and E for red rust area 70% or more. . The results are shown in Table 3.
In addition, the fraction of the austenite phase was about 15 to 40%.

As is clear from Table 3, no red rust was observed in any of the inventive examples, whereas red rust occurred in the comparative examples. That is, the welded joint of the invention example is excellent in corrosion resistance.
<Example 2>
Stainless steel having the components of steel symbols B to E shown in Table 1 was melted in a small vacuum melting furnace to obtain a 100 kg steel ingot. The obtained steel ingot was heated to 1100-1250 ° C. and hot-rolled at a finishing temperature of 750-950 ° C. to obtain a hot-rolled steel sheet having a thickness of 3.0 mm. The hot-rolled steel sheet was annealed at 800 to 1100 ° C., pickled, and then cold-rolled to obtain a cold-rolled steel sheet having a thickness of 1.5 mm. Subsequently, the cold-rolled steel sheet was subjected to finish annealing at 900 ° C., and further cooled and pickled.

  The cold-rolled steel plate was butt welded by TIG welding in combination with a stainless steel plate (SUS304 equivalent, thickness 1.5 mm) having the component of steel symbol b shown in Table 2 to produce a welded joint. The groove shape was an I groove, and the dilution ratio of the steel plate and filler wire was changed by adjusting the gap and adjusting the feed amount of the welding wire (that is, filler wire). The conditions for TIG welding are as follows.

Welding voltage: 9-12V
Welding current: 130-180A
Welding speed: 600 mm / min Electrode: 2.4 mm tungsten electrode Shielding gas component: Ar
Shield gas flow rate: 20 liter / min Back shield gas component: Ar
Back shield gas flow rate: 10 liter / min Welding wire (filler wire): Y308L
Centering on the weld bead of the obtained welded joint, a test piece with a width of 60 mm and a length of 80 mm is collected, and after removing the weld bead by machining, it is polished with # 600 abrasive paper, The temper collar by welding was removed. Next, in order to investigate the corrosion resistance of the welded joint, a combined cycle corrosion test was conducted. In the combined cycle corrosion test, salt spray (35 ° C., 2 hours, 5 mass% NaCl) → drying (60 ° C., 4 hours) → wet (50 ° C., 2 hours) was repeated for 30 cycles.

After the combined cycle corrosion test was completed, the appearance of the weld metal was visually observed to investigate the rusting situation. The rusting status was evaluated as A for no red rust, B for red rust area less than 10%, C for red rust area 10% to less than 30%, D for red rust area 30% to less than 70%, and E for red rust area 70% or more. . The results are shown in Table 4.
The fraction of the austenite phase was 10 to 35%.

  As apparent from Table 4, no red rust was observed in any of the inventive examples, whereas red rust occurred in the comparative examples. That is, the welded joint of the invention example is excellent in corrosion resistance.

Claims (3)

A weld metal of a stainless steel welded joint formed by welding a ferritic stainless steel plate and an austenitic stainless steel plate, Cr: 18 to 21% by mass, Mo: 0.1% by mass or less, Cu: 0.5% by mass or less, Ti: 0.03-0.2% by mass, Nb: 0.025% by mass or less, N: 0.04% by mass or less, Cr equivalent calculated by the following formula (1) satisfies the range of 18-25 and the following It contains Cr, Mo, Si, Nb, Ni, C and Mn so that the Ni equivalent calculated by the formula (2) is within the range of 3 to 17, and the austenite phase fraction is 20% or more. And a weld metal of a stainless steel welded joint having a structure in which the C content of the austenite phase is 0.04% by mass or less.
Cr equivalent = [% Cr] + [% Mo] + 1.5 [% Si] + 0.5 [% Nb] (1)
Ni equivalent = [% Ni] + 30 [% C] + 0.5 [% Mn] (2)
[% Cr]: Cr content of weld metal (mass%)
[% Mo]: Mo content of weld metal (mass%)
[% Si]: Weld metal Si content (mass%)
[% Nb]: Nb content of weld metal (% by mass)
[% Ni]: Ni content (mass%) of weld metal
[% C]: C content (mass%) of the weld metal
[% Mn]: Mn content (mass%) of weld metal   The ferritic stainless steel sheet contains C: 0.030 mass% or less, N: 0.030 mass% or less, the total content of C and N is 0.050 mass% or less, Si: 0.40 mass% or less, Mn: 0.50 Contains: mass% or less, P: 0.040 mass% or less, S: 0.010 mass% or less, Cr: 20.5 to 22.5 mass%, Cu: 0.03 to 1.00 mass%, Ni: 0.8 mass% or less, Al: 0.10 mass% or less Furthermore, 1 or 2 types chosen from Nb: 0.10-1.00 mass% and Ti: 0.10-1.00% are contained, The remainder consists of Fe and an unavoidable impurity, The characterized by the above-mentioned. Weld metal of stainless steel welded joint. The ferritic stainless steel sheet contains one or more selected from V: 0.01 to 0.5 mass%, W: 0.01 to 5 mass%, and B: 0.0002 to 0.0030 mass%. Item 3. A weld metal of the stainless steel weld joint according to Item 2 .