Keeping on track

Wheel sets and axles are the workhorses of any train. The expectation is that they can operate for millions of kilometres between maintenance and refurbishment. They are some of the most expensive consumables on rail vehicles and account for a significant proportion of an operator’s maintenance budget, as they are the key to vehicle availability. The rail industry is under constant pressure to reduce costs and better serve passengers, and this must be balanced against operational performance and, above all, safety.

The growth of very high speed trains has added the need to deliver machining operations with high security and close tolerances coupled with the tougher demands of hard, difficult-to-turn materials. All wheel producers are chasing lower cost per wheel and longer insert tool life. This is at a time when materials used in advanced high-speed train wheels are getting harder and more difficult to turn. Wheels and axles are usually produced from unalloyed and alloyed steel that has tensile strengths ranging from 780 to 1,050 N/mm. When wheels are partly hardened it increases the demands on the insert, which must be able to work in different hardnesses in the same cut.

Another challenge is to choose the right tools to sustain productivity and maintain product quality. Sandvik Coromant has developed a broad range of tooling solutions to meet the varied manufacturing requirements for all railway wheel types to offer a cost-effective process, with secure production combined with reliable performance.

New wheel turning

Most of the tools used for railway wheels are unique solutions, based on machining conditions such as design of the wheel and type of machine used. All turning operations for all key wheel features such as the rim, hub and web can be carried out with the Sandvik Coromant assortment of C10 holders with square and round inserts. These tools meet the needs of many different machine types for wet processing. Under coolant for round inserts sizes 32 millimetres and 16 millimetres offer a constant flow of coolant to the critical cutting zone and provide substantial increase of lifetime to the insert. Indeed, high-precision coolant can result in insert lifetime increases of up to 80 percent.

New wheel turning – tool holding

Sandvik Coromant’s T-Max P lever clamping system is the first choice system for new wheel turning. The lever forces the insert backwards into the pocket, locating the insert firmly against two sides for stable clamping. There are eight T-Max P standard holders optimized for machining new railway wheels. This solution offers excellent chip breaking combined with process reliability and security with longer tool life.

Grades for wheel turning

Sandvik Coromant has an assortment for new wheel turning applications. In these applications the latest grade GC4325 is increasingly used as the next-generation insert grade. For re-turning wheels, Sandvik Coromant has a range of insert options that are governed by the wheel condition. GC4325
is preferably used for increasingly heavier damage.

Re-turning

Wheel re-turning can be carried out using either overfloor or underfloor machines and is carried out under dry machining conditions. When re-turning it is desirable to choose a cutting depth that is as large as possible in order to achieve short machining times. This depends on the wear conditions of the predominant part of the worn wheel. The profile may be turned in a single pass, or it may be necessary to divide the machining into several stages. The use of T-Max P for a wide range of tools, inserts and grades offers process reliability and longer tool life.

Axles

Sandvik Coromant has a standard ISO assortment of tooling solutions to meet the requirements of turning axles. Depending on customer machine setup, shank holders or Coromant Capto holders with inserts in different sizes are available that can handle all stages of turning from roughing of forged material to finishing.

New wheel turning – inserts

The inserts most suitable for new wheel turning are round positive inserts such as RCMX and RCMT for T-Max P system. Negative square inserts with T-Max P are also used for certain parts of the wheel. Round inserts are strong and can handle the varying cutting depths when turning in profiles of the new wheel. Positive inserts give less cutting force and help prevent vibrations.

Summary

Wheel and axle sets for railway locomotives and carriages need to live up to stringent operational standards. Tools for production and re-turning need to be stable and have an acceptable lifetime, dependent on the wheel type. Whether it is for producing a new wheel or re-turning a wheel and axle set, Sandvik Coromant has the right tools, good application knowledge and insight into customer needs.