| 摘要 |
<p>PURPOSE:To prevent the galvanic corrosion by forming a ceramic coated layer at least on one fitting surface of different kinds of metals having a specific gap in the axial direction of the truncated tapered screws of the pin and box of a pipe screw coupling having a metal-metal seal. CONSTITUTION:A pipe screw coupling for screwing a pin 1 having a male screw on the outer surface and a box 2 having a female screw on the inner surface which are made of different kinds of metals consists of a screw having the screw gap in the axial direction of a trapezoidal tapered screw of 0.1-0.3mm. An insulating coated layer 7 is formed at least on one fitting surface of a fitted part having a metal-metal sealing part 8 of the pin 1 and the box 2. Al2O3, MgO, CaO, etc., as insulating ceramics for the coating material are applied in single or composite form on the fitting surface through the metallizing method or vaporization method, without exposing the base iron, and the screw gap is set to two times of the coating thickness. Accordingly, the breakage of the coating due to the interference on the flank surface of the screw is prevented, and the electrical insulation can be achieved.</p> |
