Material development

A good wheel is made up of one third steel.
And two thirds experience.

The secret of a good wheel lies in the material and its properties. And of course, in its production. Both – material development and production process – are practically one and the same in Bochum. So it is not a case of developing on paper and then forging, but a process in which theory and practice mutually influence and correct each other. This of course costs time and money – but the results are worth it.

Further development of standard steels

Know-how and experience are – in addition to the material – the key to service life, i.e. the mileage of the wheels. The main discipline here is the optimisation of ongoing materials within existing standards. This simplifies the approval process and brings advantages at the new development level.

Customer requirements: Hardening ER8 steels for use in harsh environmental and service conditions

ER8 and ER8C standard materials, which used to be the norm on high-speed lines in China, have reached their limits due to sometimes challenging environmental and usage conditions. In close cooperation with the customer, we proceeded to explore the possibilities of a maximum increase in hardness while maintaining the challenging material characteristics such as strength and notch impact energy in the rim and fillet as well as the metallographic specifications regarding microstructure, purity and grain size.

Our solution: UltraDur ER8H with 265HBW hardness value around the wheel

Together with our customer, we decided to increase the hardness of the material ER8 from 245HBW to 265HBW, thus substantially improving ER8 within the technical limits. The result is a high-speed wheel that sets new standards in terms of smooth running and mileage while maintaining all the parameters required by the customer and has also proven its worth under extraordinary environmental and operating conditions.

New material developments

New material developments are comprehensive research projects – always carried out in close cooperation with our customers. They are especially useful where standard limits are being drawn closer and new tasks require new solutions. An example:

Customer requirements: Over 40 tonnes per wheelset in continuous operation

OEMs and operators increasingly expect high-strength, high-performance and fatigue-resistant heavy-duty wheelsets for loads over 40 t per wheelset, which can also be used economically for loads under 30 t. Since the common materials, such as Class C according to AAR, already show significant damage to the wheel treads at loads of over 30 t, we have developed a special steel in cooperation with our customers.

BVV-Solution: Our niobium-based micro-alloyed steel HHR5

After an intensive test series we decided on a micro-alloy with niobium. Niobium, a rare heavy metal, with its exceptional affinity for carbon, is ideal for forming a high-strength alloy with a fine-grained bainitic-perlitic microstructure.

HHR5 meets all AAR Class D criteria for hardness, fracture toughness, strength properties and fatigue resistance. From this we then forge the high-performance and wear-resistant wheels, which make the carriages more resilient and freight transportation more economical.

Tried and tested BVV high-tech materials

BVV has a long tradition in material development. Results have been achieved that are repeatedly demanded by public transportation services for retrofitting, due to their excellent mileage and durability, particularly in the field of wheel tyres for local and public passenger transport.

Excelsior®, graded according to the strength levels N, H and SO, is mainly used for resilient wheels in local public transport due to its significantly improved strength and wear resistance compared to standard materials.

Excellent, it has been specially developed as a wheel tyre for driven and trailing wheelsets. With its advantages regarding wear behaviour and thermal shock behaviour with high tensile strength and good cyclic stress-strain behaviour, it is an ideal endurance runner on all rail lines.

In principle, all BVV materials naturally comply with the generally valid wheel and tyre standards EN, JIS, AAR, GOST, UIC and TJ/CL276.