Abstract Disclosed are a welded pipe with an excellent corrosion resistance, having two plate layers on the inner surface thereof, and a method of manufacturing it. The inner surface is coated with the plate layers even on the bead part and other steel foundation-exposed parts. A first plate layer of at least one of Ni, Co and Ni- or Co-base alloys is formed on at least one surface of a steel strip, then a second plate layer made of a metal or alloy having a lower melting point than the metal or alloy of forming the first plate layer is formed over the first plate layer. The thus plated steel strip is formed into a pipe and then heat-treated to give a welded pipe having no exposed steel foundation. The welded pipe has excellent corrosion resistance and workability.
A welded pipe, having excellent corrosion resistance at least on an inner surface thereof, comprising: metal strip welded together to form said pipe comprising a welding bead; a first plated layer, comprising Ni, Co and Ni- or Co-base alloys, disposed on the inner surface of said welded metal strip; and a second plated layer, comprising a single metal or alloy having a lower melting point than said first layer, disposed over said first layer and substantially covering said bead.
Claim 2
Dependent Claim
79 words
A welded pipe, having excellent corrosion resistance at least on an inner surface thereof, comprising: metal strip welded together to form said pipe comprising a welding bead; a first plated layer, comprising Ni, Co and Ni- or Co-base alloys, disposed on the inner surface of said welded metal strip; and a second plated layer, comprising a single metal or alloy having a lower melting point than said first layer, disposed over said first layer and substantially covering said bead.
Claim 3
Dependent Claim
30 words
The welded pipe having an excellent inner surface corrosion resistance as claimed in claim 1, further including a diffusion layer between said first plated layer and said second plated layer.
Claim 4
Dependent Claim
35 words
The welded pipe having an excellent inner surface corrosion resistance as claimed in claim 1 or 2, in which the second plated layer comprised at least one of sn, Sn-Zn, Sn-Ni, Ni-P, Ni-B and Ni-Zn.
Claim 5
Dependent Claim
35 words
The welded pipe having an excellent inner surface corrosion resistance as claimed in any one of claims 1 to 3, further comprising a subbing plate layer between said inner surface and said first plated layer.