The background
The key to the safe transportation of humans and goods lies, to a significant extent, in the systematic and judicious care with which rail infrastructure is maintained. Every year rail companies spend enormous amounts of money in their attempts to ensure that rail tracks are kept in good condition.

 

Conventional pearlite rail steels have undergone incremental increases in hardness to address the problem of degradation of tracks. In recent years heat treatment has been widely used to refine the microstructure to produce harder and more wear-resistant rails. These have been successful and account for, typically, 25 percent of world rail demand.

 

Considerable research has also been carried out into the potential use of other steel microstructures, including bainitic and martensitic steels, but these have made minimal impact on the market thus far.

 

There are three dominant failure modes for rail in most railways: wear, plastic deformation and rolling contact fatigue (cracking). Heat-treated rails have been successful in improving the wear performance and resistance to plastic deformation of rail, as compared with standard grades, especially on heavy haul railways where wear and plastic deformation are the dominant forms of rail degradation. However, many experts believe that there is an unavoidable balance to be struck, with softer rail required to control cracking and harder rail to control wear.

 

Network Rail, a customer, approached Tata Steel’s Europe operations for help in optimising the rail-wheel interface and to develop a rail-grade strategy that would minimise their cost. Initial investigation was focused on performance on track, to understand degradation mechanisms and the attributes required in a rail to offer improved performance. This was then used to guide laboratory research to develop an improved rail.

 

The innovation
The team, led by Dr Jay Jaiswal, began by challenging the prevalent belief that increasing hardness was the only way to build resistance against wear. They experimented with the microstructure of rail steels to develop rail steel with improved resistance to wear and a step change in resistance to rolling contact fatigue.

 

Company: Tata Steel’s Europe operations Innovation: Tata Steel HPrail Team: George Ibbeson, Dr Jay Jaiswal, Dr Howard Smith, Andrew Wilson, Dale Winney

They used a three-pronged approach to metallurgically engineer the pearlite microstructure in an attempt to reduce the incidence of ratcheting, which denoted cumulative plastic strain. This approach required an increase in the carbon and silicon content, and additions of vanadium. The result was the development of HPrail®, high-performance steel, which was initially tested in seven sites in England and is now being introduced widely across the network.

 

The payoff
On the first HPrail trial site, the cost of 1,208m of HPrail was about 10 percent higher than standard rail, an increase of about £4,000. This amount was more than recovered six months later, when the customer realised savings of close to £5,000 from not having to undergo two cycles of maintenance. At this one site alone, Network Rail has projected savings on maintenance and inspection over a five-year period of £140,000 relative to standard rail, which translates into more than three times the cost of the rail.

 

In the United Kingdom alone, the objective is to grow sales to 40ktpa to address the high-duty areas of corners and also switches and crossings. Additional profit for Tata Steel of £2.4 million per year is projected for this volume of sales. The income-generating potential of this innovation will be multiplied as the product is introduced in other countries in the European Union and beyond.

 

Network Rail was delighted with the HPrail development and it has been fully engaged in trials, benefit evaluation and approval for widespread use across their network.

 

For Tata Steel, HPrail enhances its rail-products portfolio, differentiating it from competitors. HPrail has already been granted a European patent, which will benefit Tata Steel. This is also an environment-friendly product, reducing the carbon footprint of rail by over 50 percent over its lifecycle (when compared with standard-grade rail). Tata Steel’s Europe operations has the satisfaction of having risen admirably to a difficult challenge that had been plaguing the steel rail industry for years.