1. Preparation before inspection: Remove oil, rust, and other impurities from the steel pipe surface; straighten deformed pipes; calibrate the micrometer using standard gauge blocks and the ultrasonic thickness gauge using standard test blocks. Maintain an ambient temperature of 20±5℃ to avoid thermal expansion and contraction affecting accuracy.
2. Core inspection methods:
Mechanical measurement method: Using a wall thickness micrometer with an accuracy of 0.001mm, take 8 measuring points evenly distributed around the circumference of each of the three cross-sections (ends and middle) of the steel pipe. Repeat the measurement three times at each point and take the average value. This is an industry arbitration inspection method with an accuracy of ±0.03mm.
Ultrasonic inspection method: Use a 2-10MHz digital ultrasonic thickness gauge with a coupling agent such as glycerin. Arrange the measuring points identically for each measurement. The measurement time per point is ≤1 second, enabling batch non-destructive testing with an accuracy of ±0.02mm.
Optical Inspection Method: Using laser thickness gauges and X-ray thickness gauges, adapted for ultra-high precision steel pipes used in aerospace applications, with an accuracy of ±0.01mm, local eccentricity and uneven wall thickness can be directly identified.
3. Result Judgment: According to GB/T 17395-2024 standard, the wall thickness deviation of precision seamless steel pipes is generally ≤±5%. If the difference between the maximum and minimum wall thickness of the same cross-section exceeds 10% of the nominal wall thickness, it is judged as uneven wall thickness.
