| 摘要 |
A pin-box type threaded joint for steel tubes having a contact surface (30) including a threaded portion and a nonthreaded metal-to-metal contact portion has improved leak resistance, galling resistance, and corrosion resistance particularly to crevice corrosion. The contact surface of at least one of the pin and the box is coated with a first plating layer (34) made of a Cu—Zn alloy or a Cu—Zn-M1 alloy (wherein M1 is at least one element selected from Sn, Bi, and In). Optionally, an undercoat (32) of one or both of a Ni plating layer (32a) and a Cu plating layer (32b) and an overcoat of a Sn-M2 alloy plating layer (36) (wherein M2 is one or more elements selected from Bi, In, Ni, Zn, and Cu) may be formed below and above the first layer, respectively. A solid lubricating coating (38a) and a viscous liquid or semisolid lubricating coating (38b) may also be formed atop the plating layer as a lubricating coating (38).
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