Identification of the root cause of failure in fractured and defective rails.

Synopsis

It is current practice to adopt welded joints on crossing installations that would have previously been formed using a bolted fishplate connection. The connection for this project comprised a welded tri-metal joint formed between pearlitic rail, cast manganese steel and stainless steel. Due to the expertise Corus has of a specific process– (flash butt welding) and the associated metallurgy, the client requested we identify the root cause of failure from several fractured and defective samples.

Key Client Issues

A visual examination of the fractured rail samples revealed a fatigue type defect, but it did not have a conventional appearance. There was little understanding of the root causes of failure and the propagation of the rail defects leading to:

• Broken and / or defective rail crossings in track
• Potentially increased passenger safety risks
• Disruption of services
• Expensive track component replacement costs

Recommendations were required on how to alleviate the problem.

Solutions

Since 2000, Corus have delivered a service to analyse broken and defective railway components. Having extensive metallurgical expertise and a rail manufacturing background, Corus were the client’s preferred supplier for this investigation. Our recommendations included:

• The client should be provided with a full audit trail of the crossing manufacturers production process
• A more robust inspection procedure should be implemented throughout the manufacturing process
• A follow up technical study covering rail preparation for welding, the welding procedure and heat treatment of each welded joint

Client Benefits

The investigations undertaken by CRT provided the client with:

• An understanding of the root causes of the identified failure
• A modified production process - provided by a supplier
• Potential reduction in operational disruption and costs associated with track component replacement or damage due to component failures