Threaded joint for steel pipes
A technology for threaded joints and pipes, applied in the direction of threaded connections, pipes/pipe joints/fittings, threaded fasteners, etc., can solve the problems of ineffective protection of porous solid lubricating coatings, deterioration of surface appearance, and degradation of coating lubricating properties, etc. problems, to avoid the deterioration of the surface appearance, to avoid the lubricity and deterioration of the surface, and to achieve the effect of excellent wear resistance
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Embodiment 1
[0112] The surface of the male thread and the surface of the female thread of the carbon steel threaded joint having the composition A shown in Table 1 were respectively subjected to the following surface treatments.
[0113] The surface of the female thread polished by mechanical grinding (surface roughness of 3 μm) was dipped in a manganese phosphate treatment solution (manganese phosphate type phosphate treatment solution) at 80-95°C for 10 minutes for pre-surface treatment to form an initial coating layer, the initial coating is a manganese phosphate coating with a thickness of 15 μm. On this primary coating layer, a solid lubricating coating layer having a thickness of 30 μm was formed from an epoxy resin containing graphite powder having an average particle diameter of 10 μm and copper flake powder having a maximum length of 15 μm. In the solid lubricating coating, the mass ratio of graphite to epoxy resin (M in Table 2) was 0.6:1, and the mass ratio of copper powder to ...
Embodiment 2
[0117]In exactly the same manner as described in Example 1, the surfaces of the male and female threads of the carbon steel threaded joints having the composition A shown in Table 1 were respectively surface treated.
[0118] Thus, the female thread surface has an innermost coating of manganese phosphate, an intermediate solid lubricating coating of graphite and copper powder contained in epoxy resin, and an outermost solid anti-corrosion coating of epoxy resin. The male thread surface has a zinc phosphate coating underneath and a solid anti-corrosion coating of epoxy resin above.
[0119] The surface of the female thread is exposed to the salt spray test. By observing the surface of the female thread after 100 hours of salt spray test, it was found that there was no change in the surface appearance. In the fastening and loosening test, as shown in Table 3, no galling and abrasion occurred during 10 cycles of fastening and loosening, and the results were excellent.
Embodiment 3
[0121] The surface of the male thread and the surface of the female thread of the threaded joint manufactured from the Cr-Mo steel having the composition B in Table 1 were respectively subjected to the following surface treatments.
[0122] The surface of the female thread polished by mechanical grinding (surface roughness of 3 μm) was subjected to pickling for pre-surface treatment to obtain a surface roughness of 10 μm. On the surface of the female thread that had been treated in this way, a solid lubricating coating having a thickness of 30 μm was formed from an epoxy resin containing molybdenum disulfide powder having an average particle diameter of 5 μm. In the solid lubricating coating, the mass ratio M of molybdenum disulfide to epoxy resin is 0.7:1. On this solid lubricating coating, a solid anticorrosion coating formed of epoxy resin alone was formed to a thickness of 20 μm.
[0123] The surface of the male thread polished by mechanical grinding (surface roughness of...
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Abstract
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