Method for producing TIG welded stainless steel tube, TIG welded stainless steel tube, and TIG welded stainless member
The present invention provides a method for producing a TIG-welded stainless steel tube without adding H 2 to a shielding gas, while inhibiting generation of a weld defect. The method is a method for producing a TIG-welded stainless steel tube and includes the steps of bending a stainless steel strip in a width direction so as to butt both edges against each other and TIG-welding the both edges thus butted. A pulse waveform of a pulse frequency of 40 Hz to 300 Hz is used as a current waveform of a welding power source.
1. A method for producing a TIG-welded stainless steel tube that excels in welding quality, said method comprising the steps of:
bending a stainless steel strip in a width direction so as to butt both edges against each other; and
TIG-welding the both edges thus butted,
the stainless steel strip being a ferrite-based stainless steel strip,
an inert gas to which H 2 has not been added being used as a shielding gas,
a pulse waveform of a pulse frequency of 40 Hz to 300 Hz being used as a current waveform of a welding power source,
wherein a weld bead that is formed on a surface of the welded stainless steel tube has a ratio of variation of 5% or lower, the ratio of variation being represented by a formula (1) below:
(Ratio of variation)=(| X B −X C |/X C ) (1)
where X B is a width that is of the weld bead and is in a direction perpendicular to a welding direction, and X C is a standard value of the width,
wherein a composition of the stainless steel strip contains 0.01% by weight to 0.6% by weight of Ni.
2. The method as set forth in claim 1 , wherein a composition of the stainless steel strip contains 11% by weight to 35% by weight of Cr.
3. The method as set forth in claim 1 , wherein the number of weld defects in a weld bead that is formed on a surface of the welded stainless steel tube is 0.5 or less per 1 m of the welded stainless steel tube.
4. A TIG-welded stainless steel tube comprising:
a TIG-welded part that is formed by bending a stainless steel strip in a width direction and TIG-welding both edges of the stainless steel strip,
a composition of the stainless steel strip containing 11% by weight to 35% by weight of Cr and 0.01% by weight to 0.6% by weight of Ni,
the stainless steel strip being a ferrite-based stainless steel strip, and
the number of weld defects in a weld bead that is formed in the TIG-welded part is 0.5 or less per 1 m of the TIG-welded part,
wherein the weld bead has a ratio of variation of 5% or lower, the ratio of variation being represented by a formula (1) below:
(Ratio of variation)=(| X B −X C |/X C ) (1)
where X B is a width that is of the weld bead and is in a direction perpendicular to a welding direction, and X C is a standard value of the width.
5. A TIG-welded stainless steel member comprising a TIG-welded stainless steel tube recited in claim 4 .
6. The method as set forth in claim 2 , wherein the number of weld defects in a weld bead that is formed on a surface of the welded stainless steel tube is 0.5 or less per 1 m of the welded stainless steel tube.
7. A TIG-welded stainless steel member comprising a TIG-welded stainless steel tube recited in claim 4 .
8. The method as set forth in claim 1 , wherein the composition of the stainless steel strip contains:
0.17% by weight to 0.44% by weight of Nb, and
0.12% by weight to 0.35% by weight of Mo.
9. The TIG-welded stainless steel tube as set forth in claim 4 , wherein the composition of the stainless steel strip contains:
0.17% by weight to 0.44% by weight of Nb; and
0.12% by weight to 0.35% by weight of Mo.