As self drilling bolt’s raw material, seamless steel tube’s quality must be completely inspected according to product standard and technical specification. Specific inspection includes steel tube’s chemical component analysis, geometric dimension inspection, surface quality inspection, physical and chemical properties inspection, processing property inspection, metallographic analysis, thread inspection and measurement. The purpose is to ensure quality of steel tube and meet relevant standard code or technical condition requirement.
1. Steel tube’s chemical component analysis.
Steel tube’s chemical component analysis can adopt method of chemical analysis or instrumental analysis. Chemical analysis method refers to an analysis method basing on material’s chemical reaction. Instrumental analysis method refers to an analysis method basing on material’s physical or physical and chemical properties. The common instruments for chemical component analysis are: infrared carbon-sulfur analyzer, direct-reading spectrometer and x-ray fluorescence spectroscopy.
2. Steel tube’s dimension and appearance inspection.
Inspection of steel tube’s dimension includes: wall thickness, external diameter, length, torsion resistance, ovality, bevel angle and truncated edge.
3. Steel tube’s surface quality inspection.
Steel tube’s surface quality inspection includes artificial visual inspection and non-destructive inspection. Artificial visual inspection requires sufficient lighting condition. According to standard and experience, marking defects on steel tube by special symbols. Non-destructive inspection has many methods, including ultrasonic flaw detection, eddy current inspection, magnetic powder inspection, magnetic-leak flaw detection, electromagnetic ultrasonic flaw detection and penetration inspection.
4. Steel tube’s physical and chemical properties inspection.
Steel tube’s physical and chemical properties inspection include mechanical property test (tensile test, toughness test and hardness test), hydraulic pressure test and corrosion test (intergranular corrosion test, IIC and SSCC).
5. Steel tube’s processing property inspection.
According to steel tube’s different specification and application, processing property inspection includes flattening test, ring tensile test, flaring test, flange test and bending test.
6. Steel tube’s metallographic analysis.
Steel tube’s metallographic analysis includes microstructure test and macrostructure test. Microstructure test is a method to evaluate internal material’s organization structure and defect through microscopic examination. Macrostructure test, also called macroscopic analysis, is a method to evaluate material macrostructure’s defect through artificial naked eye or magnifying glass below ten times.