FERRITIC STAINLESS STEEL FOR HOT-WATER TANK WITH WELDED STRUCTURE, AND HOT-WATER TANK
Disclosed is a ferritic stainless steel for hot-water tanks with welded structure, comprising, in terms of % by mass, at most 0.02% of C, from 0.01 to 0.30% of Si, at most 1% of Mn, at most 0.04% of P, at most 0.03% of S, from more than 21 to 26% of Cr, at most 2% of Mo, from 0.05 to 0.6% of Nb, from 0.05 to 0.4% of Ti, at most 0.025% of N, and from 0.02 to 0.3% of Al, and optionally containing at least one of at most 2%, preferably from 0.1 to 2% of Ni and at most 1%, preferably from 0.1 to 1% of Cu, with a balance of Fe and inevitable impurities.
1 . A ferritic stainless steel for hot-water tanks with welded structure, comprising, in terms of % by mass,
at most 0.02% of C,
from 0.01 to 0.30% of Si,
at most 1% of Mn,
at most 0.04% of P,
at most 0.03% of S,
from more than 21 to 26% of Cr,
at most 2% of Mo,
from 0.05 to 0.6% of Nb,
from 0.05 to 0.3% of Ti,
at most 0.025% of N,
from 0.02 to 0.3% of Al,
with a balance of Fe and inevitable impurities.
2 . A ferritic stainless steel for hot-water tanks with welded structure, comprising, in terms of % by mass,
at most 0.02% of C,
from 0.01 to 0.30% of Si,
at most 1% of Mn,
at most 0.04% of P,
at most 0.03% of S,
from more than 21 to 26% of Cr,
at most 2% of Mo,
from 0.05 to 0.6% of Nb,
from 0.05 to 0.3% of Ti,
at most 0.025% of N,
from 0.02 to 0.3% of Al,
and further containing at least one of at most 2% of Ni and at most 0.1% of Cu,
with a balance of Fe and inevitable impurities.
3 . A ferritic stainless steel for hot-water tanks with welded structure, comprising, in terms of % by mass,
at most 0.02% of C,
from 0.01 to 0.30% of Si,
at most 1% of Mn,
at most 0.04% of P,
at most 0.03% of S,
from more than 21 to 26% of Cr,
at most 2% of Mo,
from 0.05 to 0.6% of Nb,
from 0.05 to 0.3% of Ti,
at most 0.025% of N,
from 0.02 to 0.3% of Al,
and further containing at least one of from 0.1 to 2% of Ni and from 0.1 to 1% of Cu,
with a balance of Fe and inevitable impurities.
4 . A ferritic stainless steel for hot-water tanks with welded structure, comprising, in terms of % by mass,
at most 0.02% of C,
from 0.01 to 0.30% of Si,
at most 1% of Mn,
at most 0.04% of P,
at most 0.03% of S,
from more than 21 to 26% of Cr,
at most 2% of Mo,
from 0.05 to 0.6% of Nb,
from 0.05 to 0.4% of Ti,
at most 0.025% of N,
from 0.02 to 0.3% of Al,
with a balance of Fe and inevitable impurities.
5 . A ferritic stainless steel for hot-water tanks with welded structure, comprising, in terms of % by mass,
at most 0.02% of C,
from 0.01 to 0.30% of Si,
at most 1% of Mn,
at most 0.04% of P,
at most 0.03% of S,
from more than 21 to 26% of Cr,
at most 2% of Mo,
from 0.05 to 0.6% of Nb,
from 0.05 to 0.4% of Ti,
at most 0.025% of N,
from 0.02 to 0.3% of Al,
and further containing at least one of at most 2% of Ni and at most 1% of Cu,
with a balance of Fe and inevitable impurities.
6 . A ferritic stainless steel for hot-water tanks with welded structure, comprising, in terms of % by mass,
at most 0.02% of C,
from 0.01 to 0.30% of Si,
at most 1% of Mn,
at most 0.04% of P,
at most 0.03% of S,
from more than 21 to 26% of Cr,
at most 2% of Mo,
from 0.05 to 0.6% of Nb,
from 0.05 to 0.4% of Ti,
at most 0.025% of N,
from 0.02 to 0.3% of Al,
and further containing at least one of from 0.1 to 2% of Ni and from 0.1 to 1% of Cu,
with a balance of Fe and inevitable impurities.
7 . The terrific stainless steel for hot-water tanks with welded structure as claimed in claim 1 , wherein the corrosion resistance level of the steel is such that, when the steel is worked into a cold-rolled, annealed and acid-washed steel sheet, then the steel sheet is TIG-welded with no back gas sealing, and the test piece having the welded part directly as it is untreated is tested in a dipping test where the test piece is dipped in an aqueous solution with 2000 ppm of Cl − at 80° C. for 30 days (using a Pt assistant cathode), and after the test, the corrosion depth is at most 0.1 mm.
8 . A hot-water tank with welded structure, which has a welded part formed by TIG-welding with no back gas sealing of a steel material comprising the stainless steel of claim 1 , and which is used in such a manner that the TIG-welded part on the back bead side thereof is, directly as it is with no treatment given thereto, exposed to hot water.