Galvanized steel pipe

Abstract

Ensure corrosion resistance in and around the welded area. [Solution] A plated steel pipe, wherein at least the outer surface of the plated steel pipe has a coating layer containing a Zn-Al-Mg-Si alloy plating layer on a steel substrate, and in any cross-section obtained by cutting the plated steel pipe in the diameter direction perpendicular to the longitudinal direction, the coating layer has a region A on the surface of the steel substrate where Fe-Al-Si intermetallic compounds are not continuously present for 20 μm or more, the circumferential length of region A is 4 mm or less, and region A has a metal layer containing one or more metals, either Zn or Al, and the minimum thickness of the coating layer in region A is 3 μm or more.

Claims

1. It is a plated steel pipe, At least the outer surface of the plated steel pipe has a coating layer containing a Zn-Al-Mg-Si alloy plating layer on the steel substrate. In any cross-section obtained by cutting the aforementioned plated steel pipe in the radial direction perpendicular to the longitudinal direction, The aforementioned coating layer is The surface of the steel substrate has a region A in which Fe-Al-Si intermetallic compounds are not continuously present for 20 μm or more. The circumferential length of region A is 4 mm or less. In the region A, there is a metal layer containing one or more metals, namely Zn and Al. The minimum thickness of the coating layer in region A is 3 μm or more. Galvanized steel pipe.

2. The aforementioned coating layer is Region A has a region B that extends 1 mm in the circumferential direction from the end of region A in the opposite direction to region A, The plated steel pipe according to claim 1, wherein the region B has the Zn-Al-Mg-Si alloy plating layer, and the Zn-Al-Mg-Si alloy plating layer has a metal layer containing one or more metals, either Zn or Al.

3. The aforementioned coating layer is Region C is a region that is 1 mm in the circumferential direction at any position within a range of 10 to 15 mm in the circumferential direction from the end of region A in the opposite direction to region A. The average thickness of the Zn-Al-Mg-Si alloy plating layer in region B is 50% or more of the average thickness of the coating layer in region C. The plated steel pipe according to claim 2, wherein the minimum thickness of the coating layer in region B is 3 μm or more.

4. The plated steel pipe according to any one of claims 1 to 3, wherein the region A is a region that covers the welded portion of the base steel pipe constituting the plated steel pipe.

5. The Zn-Al-Mg-Si alloy plating layer is, by mass%, Al: more than 15.0% but not more than 30.0%, Mg: more than 5.0 and 15.0% or less, Si: 0.01% or more and 0.75% or less, The plated steel pipe according to any one of claims 1 to 3, having a chemical composition consisting of the remainder being Zn and impurities.

6. The Zn-Al-Mg-Si alloy plating layer is, by mass%, Al: more than 15.0% but not more than 30.0%, Mg: more than 5.0 and 15.0% or less, Si: 0.01% or more and 0.75% or less A plated steel pipe according to claim 1 or 2, which contains, and further contains one or more elements selected from the group consisting of element groups A to E below, with the remainder being Zn and impurities, having a chemical composition. [Element group A]: Fe: 5.00% or less [Element Group B]: One or more elements selected from the group consisting of Ti: 0.25% or less, Ni: 1.00% or less, and Co: 0.25% or less. [Element group C]: Sn: 0.70% or less [Element group D]: Ca: 0.60% or less [Element group E]: B: 0.50% or less

7. The Zn-Al-Mg-Si alloy plating layer is, by mass%, Al: more than 15.0% but not more than 30.0%, Mg: more than 5.0 and 15.0% or less, Si: 0.01% or more and 0.75% or less The plated steel pipe according to claim 3, further containing one or more elements selected from the group consisting of element groups A to E below, with the remainder being Zn and impurities, having a chemical composition. [Element group A]: Fe: 5.00% or less [Element Group B]: One or more elements selected from the group consisting of Ti: 0.25% or less, Ni: 1.00% or less, and Co: 0.25% or less. [Element group C]: Sn: 0.70% or less [Element group D]: Ca: 0.60% or less [Element group E]: B: 0.50% or less

8. The plated steel pipe according to claim 7, wherein the Zn-Al-Mg-Si alloy plating layer having at least one of region B and region C has a chemical composition having the element group A.

9. The plated steel pipe according to claim 7, wherein the Zn-Al-Mg-Si alloy plating layer having at least one of region B and region C has a chemical composition having the element group B.

10. The plated steel pipe according to claim 7, wherein the Zn-Al-Mg-Si alloy plating layer having at least one of the region B and the region C has a chemical composition having the element group C.

11. The plated steel pipe according to claim 7, wherein the Zn-Al-Mg-Si alloy plating layer having at least one of the region B and the region C has a chemical composition having the element group D.

12. The plated steel pipe according to claim 7, wherein the Zn-Al-Mg-Si alloy plating layer having at least one of region B and region C has a chemical composition having the element group E.

Images