1. Raw material preparation
Select API standard steel such as J55, N80, or P110
Steel grade identification through eddy current testing
Control the cutting length error of the pipe blank within ± 0.5mm
2. Rough machining stage
Use a coupling cutting machine to complete the fixed length cutting of the pipe blank
Band saw machining outer circular reference surface
CNC lathe rough inner and outer diameters, with reserved 0.3-0.5mm precision machining allowance
3. Thread processing
Using a 1:16 taper CNC lathe to machine API standard threads
Hook type thread design (bearing angle -3 °) to prevent loosening
The thread diameter tolerance is controlled within ± 0.002 inches
4. Heat treatment and surface treatment
Perform quenching and tempering heat treatment on steel grades above N80
Phosphating treatment forms an anti-corrosion layer
Copper plating process (current density 3-5 A/dm ²)
5. Quality inspection
Three coordinate measurement of thread geometric parameters
Wet magnetic particle inspection for detecting surface defects
100% full inspection of thread fit for the pass stop gauge
6. Finished product processing
Coupling painting and rust prevention treatment
Laser marking records steel grade and batch information
Special packaging to prevent transportation damage
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