Ductile Plus

Since 2005, Brechmann-Guss has been producing specialty cast irons with spherical graphite according to internal company standards. These standards are used to regulate the pearlite/ferrite ratio in the metal’s atomic structure; the optimum ratio leads to strain properties in the final product which exceed (by a wide margin) the minimum values required at the time by the European Standard DIN EN 1563. Even after the introduction of solid solution strengthening in ferritic materials, which was added to and improved the level given in the standards in 2011, Brechmann’s specialty alloy (EN-) GJS 520-15 still guarantees more than twice as much strain (and therefore offers additional operational safety and reliability) as that of the standard-quality alloy.

Our Duktil Plus material is primarily used for dynamically loaded components, parts with complicated geometries, parts requiring extensive mechanical finishing, and thin-walled designs. Duktil Plus is also suitable as an alternative to certain low-alloyed cast steels, forging steels, and welded parts.

Our goal in developing specialty materials such as Duktil Plus was, first and foremost, to produce a material that possessed several advantages over conventional, standardized cast irons. These materials, with their higher strength and, simultaneously, high ductility, offered then and still offer now other advantages (in addition to significantly increased fracture strain) compared to the classic EN-GJS materials (represented here by GJS 520-15, usually used in ball hitches):

• Increase of the 0.2% strain-boundary from 320 up to at least 360 N/mm2, making them suitable for use under higher loads than previously
• Good machinability, meaning an increase in cutting speed and/or in tool service life of ca. 10%-20%
• Increase in fatigue strength for dynamic loading in comparison to EN-GJS-500-7
• Isotropy (physical properties are identical regardless of orientation), due to a uniform microstructure
• Similar shrinkage behaviour to EN-GJS-500-7, making it possible to use existing models and patterns

Among other things, Brechmann-Guss produces lever arms for swing axle suspensions, steering units, spokes and gear carriers, clamping yokes, tie rod bolts, or ball hitches for caravans/trailers from Duktil Plus; together, these are all parts that are typically subjected to higher loading – but above all, they are parts that are critical for operational safety.

The advantage offered by double the normal amount of strain with regard to part safety goes without saying, especially for safety-critical components – and becomes even clearer when looking at results from the most widely-used test in material sciences, the tensile test. Specimens with low strain will fracture almost at once; ductile specimens, on the other hand, can be considerably stretched out before fracturing.

In extreme cases, it can even be possible to twist SG cast iron specimens a full 360° without causing them to break – and that, in practical terms, means that a damaged component made of GJS 520-15 is going to “rattle and shake” – i.e., is going to provide warning signs – before it fails completely.