METHOD FOR MAKING A HOT WATER TANK OF FERRITIC STAINLESS STEEL WITH A TIG WELDED STRUCTURE
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 - 8 . (canceled)
9 . A method of making a hot water tank with a TIG-welded structure comprising the steps of:
providing an upper end plate, a lower end plate, and a shell plate, that when welded together form the hot water tank, each of the upper end plate, the lower end plate and the shell plate comprising a ferritic stainless steel, the ferritic stainless steel having a composition 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;
positioning the upper and lower edges of the shell plate to contact outside surfaces of the upper and lower end plates, respectively, with a lower edge of the upper end plate and an upper edge of the lower end plate extending along an inner surface of the shell plate; and
TIG-welding the upper and lower edges of the shell plate to the outside surfaces of the upper and lower end plates, respectively, with no back gas sealing during the TIG-welding step.
10 . A method of making a hot water tank with a TIG-welded structure comprising the steps of:
providing an upper end plate, a lower end plate, and a shell plate, that when welded together form the hot water tank, each of the upper end plate, the lower end plate and the shell plate comprising a ferritic stainless steel, the ferritic stainless steel having a composition 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,
positioning the upper and lower edges of the shell plate to contact outside surfaces of the upper and lower end plates, respectively, with a lower edge of the upper end plate and an upper edge of the lower end plate extending along an inner surface of the shell plate; and
TIG-welding the upper and lower edges of the shell plate to the outside surfaces of the upper and lower end plates, respectively, with no back gas sealing during the TIG-welding step.
11 . A method of making a hot water tank with a TIG-welded structure comprising the steps of:
providing an upper end plate, a lower end plate, and a shell plate, that when welded together form the hot water tank, each of the upper end plate, the lower end plate and the shell plate comprising a ferritic stainless steel, the ferritic stainless steel having a composition 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,
positioning the upper and lower edges of the shell plate to contact outside surfaces of the upper and lower end plates, respectively, with a lower edge of the upper end plate and an upper edge of the lower end plate extending along an inner surface of the shell plate; and
TIG-welding the upper and lower edges of the shell plate to the outside surfaces of the upper and lower end plates, respectively, with no back gas sealing during the TIG-welding step.
12 . A method of making a hot water tank with a TIG-welded structure comprising the steps of:
providing an upper end plate, a lower end plate, and a shell plate, that when welded together form the hot water tank, each of the upper end plate, the lower end plate and the shell plate comprising a ferritic stainless steel, the ferritic stainless steel having a composition 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,
positioning the upper and lower edges of the shell plate to contact outside surfaces of the upper and lower end plates, respectively, with a lower edge of the upper end plate and an upper edge of the lower end plate extending along an inner surface of the shell plate; and
TIG-welding the upper and lower edges of the shell plate to the outside surfaces of the upper and lower end plates, respectively, with no back gas sealing during the TIG-welding step.
13 . A method of making a hot water tank with a TIG-welded structure comprising the steps of:
providing an upper end plate, a lower end plate, and a shell plate, that when welded together form the hot water tank, each of the upper end plate, the lower end plate and the shell plate comprising a ferritic stainless steel, the ferritic stainless steel having a composition 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,
positioning the upper and lower edges of the shell plate to contact outside surfaces of the upper and lower end plates, respectively, with a lower edge of the upper end plate and an upper edge of the lower end plate extending along an inner surface of the shell plate; and
TIG-welding the upper and lower edges of the shell plate to the outside surfaces of the upper and lower end plates, respectively, with no back gas sealing during the TIG-welding step.
14 . A method of making a hot water tank with a TIG-welded structure comprising the steps of:
providing an upper end plate, a lower end plate, and a shell plate, that when welded together form the hot water tank, each of the upper end plate, the lower end plate and the shell plate comprising a ferritic stainless steel, the ferritic stainless steel having a composition comprising, in terms % 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,
positioning the upper and lower edges of the shell plate to contact outside surfaces of the upper and lower end plates, respectively, with a lower edge of the upper end plate and an upper edge of the lower end plate extending along an inner surface of the shell plate; and
TIG-welding the upper and lower edges of the shell plate to the outside surfaces of the upper and lower end plates, respectively, with no back gas sealing during the TIG-welding step.
15 . The method of claim 9 , 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 at 80° C. for 30 days (using a Pt assistant cathode), and after the test, the corrosion depth is at most 0.1 mm.
16 . The method of claim 9 , wherein the hot-water tank 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.
17 . The method of claim 10 , 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.
18 . The method of claim 10 , wherein the hot-water tank 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.
19 . The method of claim 11 , 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.
20 . The method of claim 11 , wherein the hot-water tank 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.
21 . The method of claim 12 , 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.
22 . The method of claim 12 , wherein the hot-water tank 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.
23 . The method of claim 13 , 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.
24 . The method of claim 13 , wherein the hot-water tank 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.
25 . The method of claim 14 , 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.
26 . The method of claim 14 , wherein the hot-water tank 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.
27 . The method of claim 9 , further comprising a plurality of shell plates and welding opposing side edges of adjacent plates together.
28 . The method of claim 10 , further comprising a plurality of shell plates and welding opposing side edges of adjacent plates together.
29 . The method of claim 11 , further comprising a plurality of shell plates and welding opposing side edges of adjacent plates together.
30 . The method of claim 12 , further comprising a plurality of shell plates and welding opposing side edges of adjacent plates together.
31 . The method of claim 13 , further comprising a plurality of shell plates and welding opposing side edges of adjacent plates together.
32 . The method of claim 14 , further comprising a plurality of shell plates and welding opposing side edges of adjacent plates together.