Welded member and method for manufacturing same
AssigneeNippon Steel Nisshin Co., Ltd.
InventorsKazuaki Hosomi, Tomokazu Nobutoki, Takefumi Nakako
Life of this patent
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Abstract
A welded member includes a hot dip Zn-based alloy coated steel sheet as a base material and has excellent corrosion resistance and weld bead shear strength. In the welded member in which a lower sheet and an upper sheet, which are hot dip Zn-based alloy coated steel sheets, are stacked and arc-welded together, a weld bead is formed so that a cross-sectional width W satisfies the following formula 2T≤W≤6T, and a blowhole occupancy Br represented by the following formula becomes not more than 50%: Br=(Σdi/L)×100, where T represents a thickness of the hot dip Zn-based alloy coated steel sheet, di represents a length of an i-th blowhole observed in X-ray radiography, and L represents a length of the weld bead.
Claims12
A welded member comprising:
- a first hot dip Zn-based alloy coated steel sheet;
- a second hot dip Zn-based alloy coated steel sheet stacked on and arc-welded to a first sheet surface of the first hot dip Zn-based alloy coated steel sheet;
- and
- a weld bead that is provided on the first sheet surface such that the first hot dip Zn-based alloy coated steel sheet and the second hot dip Zn-based alloy coated steel sheet are welded together by the weld bead,
- each of the first hot dip Zn-based alloy coated steel sheet and the second hot dip Zn-based alloy coated steel sheet having a coating weight of 15 g/m2 to 250 g/m2 per surface,
- the weld bead being formed such that a cross-sectional width W satisfies a formula (1) below and a blowhole occupancy Br represented by a formula (2) below becomes not more than 50%, the cross-sectional width W being a width of a cross section from one boundary between a Zn-based coating layer and the weld bead to the other boundary between the Zn-based coating layer and the weld bead on the first sheet surface, and the cross section being obtained by cutting the weld bead by a plane orthogonal to a direction in which the weld bead extends, the weld bead having at least two protrusion parts each of which protrudes into the first hot dip Zn-based alloy coated steel sheet in the cross section,
- a protruding length of each of the at least two protrusion parts in the first hot dip Zn-based alloy coated steel sheet being not less than 0.2 mm, and the protruding length being not greater than a thickness of the first hot dip Zn-based alloy coated steel sheet, and
- the first sheet surface being in contact with a second sheet surface of the second hot dip Zn-based alloy coated steel sheet,
- 2T≤W≤6T (1)
- Br=(Σdi/L)×100 (2)
- where:
- T represents a thickness of any of the first hot dip Zn-based alloy coated steel sheet and the second hot dip Zn-based alloy coated steel sheet and, in a case where a thickness of the first hot dip Zn-based alloy coated steel sheet is different from a thickness of the second hot dip Zn-based alloy coated steel sheet, T represents a smaller one of the thickness of the first hot dip Zn-based alloy coated steel sheet and the thickness of the second hot dip Zn-based alloy coated steel sheet;
- di represents a length of an i-th blowhole observed in X-ray radiography;
- and
- L represents a length of the weld bead.
A method for manufacturing a welded member by a pulsed arc welding process in which a second hot dip Zn-based alloy coated steel sheet that is stacked on a first sheet surface of a first hot dip Zn-based alloy coated steel sheet is arc-welded to the first hot dip Zn-based alloy coated steel sheet with an arc generated by alternately supplying a peak current and a base current, said method comprising:
- a welding step of forming a weld bead on the first sheet surface such that the first hot dip Zn-based alloy coated steel sheet and the second hot dip Zn-based alloy coated steel sheet are welded together by the weld bead,
- each of the first hot dip Zn-based alloy coated steel sheet and the second hot dip Zn-based alloy coated steel sheet having a coating weight of 15 g/m2 to 250 g/m2 per surface,
- in the welding step, the pulsed arc welding process being carried out by using, as a shielding gas, an Ar—CO2 gas whose CO2 concentration is not less than 5% by volume and not more than 20% by volume,
- in the welding step,
- (i) the weld bead being formed such that a cross-sectional width W satisfies a formula (1) below and a blowhole occupancy Br represented by a formula (2) below becomes not more than 50%, the cross-sectional width W being a width of a cross section from one boundary between a Zn-based coating layer and the weld bead to the other boundary between the Zn-based coating layer and the weld bead on the first sheet surface, and the cross section being obtained by cutting the weld bead by a plane orthogonal to a direction in which the weld bead extends,
- (ii) the arc welding being carried out such that a blowhole occupancy Br represented by a formula (2) below becomes not more than 50%, and
- (iii) the weld bead being formed such that the weld bead has a protrusion part which protrudes into the first hot dip Zn-based alloy coated steel sheet in the cross section, a protruding length of the protrusion part in the first hot dip Zn-based alloy coated steel sheet being not less than 0.2 mm, and the protruding length being not greater than a thickness of the first hot dip Zn-based alloy coated steel sheet, and
- in the welding step, a solid wire being used as a welding wire,
- 2T≤W≤6T (1)
- Br=(Σdi/L)×100 (2)
- where:
- T represents a thickness of any of the first hot dip Zn-based alloy coated steel sheet and the second hot dip Zn-based alloy coated steel sheet and, in a case where a thickness of the first hot dip Zn-based alloy coated steel sheet is different from a thickness of the second hot dip Zn-based alloy coated steel sheet, T represents a smaller one of the thickness of the first hot dip Zn-based alloy coated steel sheet and the thickness of the second hot dip Zn-based alloy coated steel sheet;
- di represents a length of an i-th blowhole observed in X-ray radiography;
- and
- L represents a length of the weld bead.
Dependencies are inferred from the claim text.