JPWO2020203931A5

JPWO2020203931A5 -

Info

Publication number: JPWO2020203931A5
Application number: JP2021512091A
Authority: JP
Filing date: 2020-03-27
Publication date: 2022-01-19
Anticipated expiration: 2040-03-27

Claims

By mass%,
C: 0.001 to 0.050%,
Si: 0.05 to 0.80%,
Mn: 0.10% to 2.00%,
Cr: 23.00 to 26.00%,
Ni: 4.50-6.00%,
Mo: 1.00 to 2.00%,
N: 0.150 to 0.250%,
Al: 0.003 to 0.050%,
Contains,
O is 0.0060% or less,
P is 0.050% or less,
S is limited to 0.0050% or less,
And the PREN value defined by the following formula (1) is 28.0 or more and 35.0 or less.
Duplex stainless steel base material with the balance consisting of Fe and impurities,
A welded joint comprising a weld metal and a welded portion including a heat-affected zone.
The components of the weld metal are composed of the components of the duplex stainless steel base material except for C, N and O.
By mass%, it contains C: 0.001 to 0.060%, N: 0.100 to 0.250%, O: 0.0100% or less.
The PREN value defined by the following equation (1) is 29.0 or more, and
The amount of austenite in the duplex stainless steel base material is 30 to 70 area%, and the amount of austenite in the weld metal and the heat-affected zone is 8 to 70 area%, respectively.
The duplex stainless steel base material has an NI value of 170 or more as defined by the following formula (2), and satisfies the following formula (3).
The weld metal is a welded joint having an NI value of 222.8 or more defined by the following formula (2) and satisfying the following formula (3) .
PREN = Cr + 3.3Mo + 16N ... (1)
NI = (Cr + Mo + 2 × Ni) / N ... (2)
N ≧ (0.08Cr + 0.08Mo-0.06Ni-1.21) /0.4 × 0.08 ... (3)
However, the element symbol in the formulas (1), (2) and (3) indicates the content (mass%) of each element.

The welded joint according to claim 1, wherein the welded portion has a pitting potential of 0.27 V vs SSE or more according to the JIS G0577 A method measured at 50 ° C.

The welded joint according to claim 1 or 2, wherein the pitting potential according to the JIS G0577 A method obtained by measuring the duplex stainless steel base material at 50 ° C. is 0.27 V vs SSE or more.

The welded joint is characterized in that the impact value when the Charpy impact test is carried out at a test temperature of −20 ° C. by the test method specified in JIS Z 2242 is 100 J / cm ² or more. The welded joint according to any one of 3.

The duplex stainless steel base material and the weld metal further have Nb: 0.150% or less in mass%.
Ti: 0.020% or less,
Ta: 0.200% or less,
Zr: 0.050% or less,
Hf: 0.080% or less,
Sn: 0.100% or less,
W: 1.00% or less,
Co: 1.00% or less,
Cu: 3.00% or less,
V: 0.300% or less,
B: 0.0050% or less,
Ca: 0.0050% or less,
The present invention according to any one of claims 1 to 4, wherein one or more of the groups consisting of Mg: 0.0050% or less and REM: 0.050% or less are contained. Welded fittings.

The welded joint according to claim 1 to 5, wherein the amount of the weld metal and the amount of austenite in the heat-affected zone are 8 to 17 area%, respectively.

By controlling the welding heat input amount Q so that the value of Nweld defined by the following formula (5) is 0.100 to 0.250, the duplex stainless steel base material is not used. The method for manufacturing a welded joint according to any one of claims 1 to 6, wherein the shield gas does not contain nitrogen.
Q = [Welding current (A)] x [Welding voltage (V)] ÷ [Welding speed (cm / s)] ... (4)
Nweld = Nbase × {0.978-0.0029 × √ (Q)} ・・・ (5)
However, in the above formula (5), Nbase indicates the nitrogen content (mass%) of the base metal, and Q indicates the welding heat input amount Q (J / cm).