Acceptance Standards and Testing Items for Externally Standardized Rails
- What does the acceptance standard for ASTM steel rails mainly include?
The ASTM steel rail acceptance standard has strict regulations on chemical composition, such as carbon content should be 0.60%-0.80%, manganese content 0.70%-1.20%, etc. The dimensional tolerance requires the rail head width deviation to be ±1.0mm and the rail height deviation ±0.8mm. In terms of mechanical properties, the tensile strength should be ≥720MPa and the elongation ≥12%. At the same time, the standard also specifies the surface quality of the rail, which must be free of cracks, scabs and other defects, and internal quality must be confirmed through non-destructive testing.
- What are the differences between the testing items of EN steel rails and national-standard steel rails?
The testing items for EN steel rails include fracture toughness test, which requires the rail to have a fracture toughness of ≥80MPa·m½ at -40℃, while there is no such mandatory requirement in national standards. In terms of non-destructive testing, EN requires 100% ultrasonic flaw detection, while national standards usually conduct sampling inspection. In addition, EN has stricter testing on the welding performance of rails, requiring simulated welding tests and testing of joint performance, while the testing of welding performance in national standards is relatively simplified.
- What are the special requirements for the appearance inspection of JIS steel rails?
JIS steel rail appearance inspection requires the rail head tread roughness Ra≤12.5μm, which is stricter than national standards. The restriction on rail curvature is more stringent, with the curvature per meter not exceeding 0.5mm and the total length curvature not exceeding 3mm. At the same time, it is required that the scratch depth on the rail surface does not exceed 0.3mm, and transverse scratches are not allowed. These requirements aim to reduce vibration and noise during train operation.
- What are the key points of mechanical property testing for UIC standard steel rails?
UIC standard steel rails focus on testing yield strength, requiring ≥450MPa, and the ratio of yield strength to tensile strength ≤0.85 to ensure sufficient plastic reserve of the rail. Impact toughness test is a key item, with impact energy at -20℃ ≥40J to ensure the rail's impact resistance in low-temperature environments. In addition, fatigue testing is required, and no cracks are allowed under 10 million cycles of load.
- How to handle unqualified items during the acceptance of foreign-standard steel rails?
If an index of foreign-standard steel rails is unqualified, such as dimensional deviation, rework can be carried out, such as grinding and correction, and re-inspection after treatment. If the material or mechanical properties are unqualified, rework is usually not allowed, and the entire batch is rejected. For minor surface defects, such as small-area rust, rust removal can be carried out and re-evaluated; if it does not affect the service performance, it can be used with downgrading. The acceptance process must record the unqualified items and handling methods in detail and archive them for traceability.