Curved sections within light rail networks demand heightened maintenance frequency due to their susceptibility to wear. Regular upkeep is crucial to guarantee the efficient and safe operation of rail systems. The rate of wear on the rails varies based on factors like traffic intensity, curvature radius, and age. However, one undeniable certainty is that neglecting timely intervention allows the wear to worsen, potentially resulting in substantial consequences for the overall integrity of rail networks.
Since its invention in the 1940s, submerged arc welding has been widely used for several reasons: increased productivity with high deposition rate, excellent weld quality, ease of use, and the fact that automation provides good traceability and quality control.
Based on a comprehensive understanding of the type of wear occurring on light rail networks and the advantages of the submerged arc welding process, Welding Alloys provides a complete solution for the maintenance of tram and metro networks. We have developed a work-hardening manganese cored wire, HARDFACE 19 9 6-S, that is designed for the preventive and remedial hardfacing of grooved rails. This, combined with our dedicated welding equipment to optimise welding efficiency, our Gauge Corner Restoration (GCR) machine, provides the ultimate solution for this type of maintenance.
Cored wire vs solid wire
The characteristics of cored wire mean it offers significant advantages over solid wire. Cored wires comprise a metal sheath (made from strip) and a core consisting of a mixture of various metallic and non-metallic powders.
When welding with a cored wire, all or nearly all of the welding current is conducted by the metal sheath. In a solid wire, however, the current travels through the entire cross-section of the wire. Given this, metal cored wires provide two main advantages:
- For a given current, a cored wire will have a higher deposition rate than a solid wire
- For a given deposition rate, a cored wire will have a lower heat input than a solid wire
In situ repair of grooved rails
Urban network maintenance predominantly occurs overnight within a brief and predetermined timeframe. Efficiency is paramount, as operators must weld a specific amount of linear meters on hard-to-weld steels, often characterised by a high carbon equivalent. Additional external factors that can also impact the maintenance of the rails include varying humidity levels and temperatures. By utilising Welding Alloys’ dedicated welding equipment and cored wire when conducting maintenance on the rails, these challenges are met with ease.
Increase deposition rate
Is it possible to increase the deposition rate without increasing the heat input? Yes, it is! Thanks to the cored wire design, using our HARDFACE 19 9 6-S with identical welding amperage and voltage, will result in an immediate increase of the deposition rate, by at least 35%.
Reduce the risk of cold cracking
Compared to solid wire, cored wire bead profiles penetrate 25% less into the base metal. This leads to a drastically reduced risk of the formation of a brittle heat affected zone (and therefore, evading the effects of spalling).
Moreover, the less we dilute into the rail, the less the base metal will admixture and the better the welding deposit, and wear resistance, will be. In other words, the welding deposit when using a HARDFACE 19 9 6-S cored wire will be more alloyed than that of a solid wire.
Limit the heat input
By adjusting the welding parameters, cored wire allows for a 30% lower heat input, without negatively impacting the deposition rate. This reduction will immediately lead to a better work environment by protecting the surrounding filling material from burning.
The benefits of using a cored wire for this application are evident. Additionally, the automatic submerged arc welding process has evolved over time with a primary objective: to combine quality with productivity. This objective can be seamlessly achieved by using Welding Alloys’ HARDFACE 19 9 6-S sub arc cored wire, in conjunction with our GCR machine for the maintenance of grooved rails. The significant process improvements attained will ultimately benefit both the rail network and its users.
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