FEATURE GEARS & GEARBOXES
stage, scrap mix and melting are the main processes that need to be controlled. At the secondary metallurgy stage, it is a case of fine tuning the alloying and degassing to produce different steel qualities. The casting process can vary widely,
and to produce clean steel, a large casting format such as ingot casting, is used. This process is flexible, gives a good starting format and, because the ingot solidifies inwards and upwards, inclusions are generally pushed towards the top, which is then cut off and scrapped. The final main production stage is
rolling, including the homogenisation/ soaking and the hot working of the material into smaller formats. Starting from a large format results in a higher area reduction/reduction ratio, which also has a huge impact on the material quality. The actual processes used to
manufacture clean steel may vary depending on the quality and grade, but to achieve the full potential of this material there can be no compromise at any stage. The objective is to produce clean steel with an optimised balance between quality and economy. It is important to note that clean steels can be produced via high volume production methods.
CLEAN STEEL TYPES Bearing Quality (BQ) – Steels are a range of clean steels with reduced defect size. The effect is to help improve design life and/or increase torque on existing generations of gears and gearboxes. Moderate design changes can also be made while securing high and consistent quality end-user products. Moving to BQ-Steel is normally the first step when upgrading from conventional steel. IQ-Steels are the next level – a range
of isotropic clean steels, designed to have small and isolated inclusions and with a fatigue performance comparable to Vacuum Arc Remelted (VAR) steels. The small and evenly sized inclusions create
offers the possibility to sustain increased loading and a better balance of life across an entire gearbox system including the bearings and housing. So, to get the most out of clean steel it is crucial for design engineers to work in close cooperation with materials engineers. This will ensure that the design complements the advantages offered by clean steel.
NEW OPPORTUNITIES There are three ways that adopting clean steel can enhance the design of gears and gearboxes: The first opportunity is in material
Figure 2 – Rotating bending fatigue test performance - conventional steel compared with BQ-Steel and IQ-Steel in both longitudinal and transversal direction
the isotropic properties that can withstand heavy loads in all directions. This makes IQ-Steel suitable for complex load cases, especially in gears. Figure 2 shows the results from RBF
testing to evaluate how different types of steel handle cyclic loading in both the normally loaded longitudinal direction as well as the transverse direction. Depending on the loading mode, both BQ-Steel and IQ-Steel offer an improvement over conventional steel.
IMPROVED FATIGUE LIFE FOR GEARS Ovako carried out a test program with WZL of RWTH Aachen University to investigate the surface fatigue of gear material. The program concluded that the quality of the steel was a determining factor in the endurance strength parameter. Furthermore, the use of clean steel offered a two-digit percentage improvement above a commonly used gear steel. While this substantial improvement is
impressive, it does not portray a complete picture of the potential benefits of clean steel. If the gear design was refined to give a better tooth meshing that allows for a higher load on the flank, then spectacular results could be achieved. This
substitution to enhance the performance of an existing design. A simple upgrade of an existing grade to IQ- or BQ-Steel versions of the same grade can boost performance with little to no design changes. Increased benefits are offered by partial
design changes. This is because the improved fatigue properties of clean steel can enable components to be downsized to create next-generation designs, such as powertrains with remarkable gains in power density. The opportunity to reduce component size and weight, with no impact on strength and durability, can make room for additional components. The result is a system with superior performance – within the same external system boundaries. The ultimate opportunity for clean steel
is offered when creating new design concepts by enabling gears, bearings and other components to be slimmed down. For example, in powertrains it can offer a major increase in power density, free up space for surrounding systems or introduce new levels of hybridization. All these new design possibilities are
offered by a focus on purity with clean steel that consistently delivers smaller- sized impurities for enhanced fatigue life.
Ovako
www.ovako.com/en/steel- portfolio/ovako-brands/iq-steel/
ABSOL DRIVEN
16 NOVEMBER 2019 | DESIGN SOLUTIONS
UTEL
For further information and sales contact Greg Smith on 01484 600200 or
greg@labtex.co.uk
Y NEW RANGE OF DRIVES AND VARIABLE SPEED GEARBOXES
www.labtex.co.uk
ATEX compliant to EC Directive 94/9/EC Distributed in the UK by:
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36
