This is the softest of the Unibar grades (120-200 HB), and is therefore recommended if your requirements are for good machinability with low requirements of tensile strength and resistance to wear.
In addition, because of its ferritic structure, it is recommended for applications requiring good thermal conductivity.
The surface finish of Unibar 200 is, however, inferior to that of the other grades, which are harder and therefore have better structural cohesion.
Unibar 250 offers a good combination of strength and wear resistance with average hardness (160-230 HB), while still possessing reasonable machinability and excellent surface finishes.
Noise and vibration damping are good in this grade.
Unibar 250+ complies with the specification GJL-250 (EN-1561) or GJL-250-C (EN-16482). Pearlitic structure, with ferritic rim, typical of concast bar, indicated in EN-16482.
Hardness of this grade is lower than the one of GJL-250 or UB250 standard.
This is one of the hardest grades (190-260 HB), and is therefore used when high tensile strength and/or resistance to wear is required, because of its pearlitic structure.
Its surface finish is better than that of other softer qualities because of its better structural cohesion, which allows surface hardening.
This is the hardest grade with the highest resistance (220-280 HB, depending on dimension).
Its most important quality is the fact that the structure is also pearlitic on the outside rim (90% pearlite), and is therefore suitable for those applications in which high resistance to wear is required in the parts close to the outside of the bar.
In addition, this quality allows surface hardening. In particular, this quality with a high phosphorus content (0.3/0.6%) is recommended when a higher resistance to wear is required than that provided by a fully pearlitic structure, as is the case with valve guides, etc.
The very hard Unibar 350 (HB-250/310) obtained using fine graphite (ID/IE) in the centre of the bar as well, constitutes one of the highest values in terms of cohesion and resistance.