What does UIC Leaflet 897-6 cover?

UIC Leaflet 897-6 covers the test procedures and acceptance criteria for the reconditioning (repair) of rails using electric arc welding, aimed at fixing surface defects like squats and wheel burns.

Why is hardness important in Chapter 8?

Hardness is critical because if the weld is too soft, it will wear out quickly (forming a dip); if it is too hard, it may become brittle or damage the train wheels. Chapter 8 requires the weld hardness to match the parent rail closely.

Extending Rail Life: Technical Specs in UIC 897-6 Chapter 8

UIC Leaflet 897-6 Chapter 8 defines the technical standards for rail reconditioning via electric arc welding. It sets critical limits for hardness, geometry, and defect acceptance.

November 24, 2023 8:11 am

What is UIC Leaflet 897-6?

UIC Leaflet 897-6 is a technical document titled “Test procedures for the acceptance of reconditioning of rails by electric arc welding.” It provides the guidelines for repairing surface defects on rails (such as squats or wheel burns) to extend their service life. Chapter 8 is the core technical section, detailing the specific Technical Specifications and acceptance criteria that the finished weld must meet to be considered safe for traffic.

Focus of Chapter 8: Acceptance Criteria

Chapter 8 focuses on the physical and metallurgical properties of the rail after the repair process. It ensures that the welding material integrates correctly with the parent rail steel without creating new weak points. The specifications cover three main areas: geometric tolerances, hardness values, and internal integrity.

Key Technical Specifications

Hardness Matching: The hardness of the deposited weld metal must match the parent rail within specific limits (typically measured in Brinell, HBW) to prevent uneven wear.
Geometric Profile: After grinding, the rail head profile must fall within strict tolerances (measured in fractions of a millimeter) to ensure smooth wheel-rail interaction.
Heat Affected Zone (HAZ): The transition zone between the weld and the rail must not exhibit brittleness or cracking.

Parameter Comparison: Before vs. After Compliance

The following table illustrates the strict technical requirements imposed by Chapter 8 to transform a damaged rail into a compliant one.

Parameter	Standard Condition (Acceptance Criteria)	Importance
Running Surface Flatness	Tolerance typically < 0.3 mm over 1 meter	Prevents dynamic impact loads on wheels.
Weld Hardness	Parent Rail ± 30 HBW (Approx.)	Ensures the weld wears at the same rate as the rail.
Ultrasonic Testing (UT)	Zero lack of fusion or porosity > defined size	Detects internal cracks invisible to the eye.
Surface Finish	Smooth ground finish (Ra value limits)	Reduces noise and initial wear.

Non-Destructive Testing (NDT) Requirements

Chapter 8 mandates rigorous testing. Visual inspection is not enough; the technical specifications require Dye Penetrant Inspection (to find surface cracks) and Ultrasonic Testing (to ensure the weld has fused completely with the rail body). Any indication of “lack of fusion” results in immediate rejection of the repair.

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