Q1: What mechanical property tests are required for 12Cr1MoVG steel pipes before shipment?
Room temperature tensile testing (yield strength ≥ 275 MPa, tensile strength 440-640 MPa) is mandatory. High temperature tensile testing (typically testing performance at 550°C) is mandatory. Impact testing (room temperature impact energy ≥ 31 J). Hardness testing (HB ≤ 170). Flattening or bend testing is performed to verify plastic deformation capacity.
Q2: How is the microstructure of 12Cr1MoVG steel pipes tested?
Prepare metallographic specimens and etch them with 4% nitric acid solution. Observe the microstructure under an optical microscope (it should be tempered bainite). Evaluate the grain size (typically requiring ≥ grade 5). Examine the distribution and morphology of carbides. Analyze the composition of the precipitated phase using a scanning electron microscope (SEM). Rating is performed according to GB/T 13298.
Q3: How is the high-temperature performance of 12Cr1MoVG steel pipe tested?
Endurance strength tests are conducted (typically testing the rupture strength at 550°C/100,000 hours). Creep tests are performed to determine the steady-state creep rate. High-temperature tensile tests measure strength at different temperatures. Oxidation tests evaluate the material's oxidation resistance. Thermal fatigue tests simulate performance changes under actual operating conditions.
Q4: What are the key points of non-destructive testing for 12Cr1MoVG steel pipe?
Ultrasonic testing (UT) detects internal defects (sensitivity: Φ2mm flat-bottom hole). Eddy current testing (ET) screens for surface and sub-surface defects. Magnetic particle testing (MT) detects surface cracks (suitable for ferromagnetic materials). Penetrant testing (PT) is used to inspect non-magnetic areas. Thickness measurement ensures that the wall thickness meets tolerance requirements.
Q5: What does the quality certification document for 12Cr1MoVG steel pipe include?
Material certificate (chemical composition, mechanical properties). Heat treatment records (temperature-time curves). Non-destructive testing report (UT/RT/MT, etc.). High temperature performance test data (such as endurance strength). Third-party inspection certificates (such as SGS, BV, etc.).
