Ovako 802F and 824B are low-alloy bearing steels with about 1% carbon. 802F is alloyed with chrome while 824B is somewhat higher alloyed and contains molybdenum in addition to chrome. As stocked, the hot-finished tubes are soft annealed in order to facilitate machining. Through quenching and tempering, the material can attain very high levels of strength and hardness comparable to those achievable via case hardening. The steels thus find application for parts other than bearings for which high surface hardness is needed.
At Tibnor, the tubes stocked are in grade 802F up to a wall thickness of 25 mm. Tubes with greater wall thicknesses, 25 - 35 mm, are in the higher-alloyed grade 824B.
As regards chemical analysis, 802F conforms fully to the requirements for grade 100Cr6 in SS-EN ISO 683 - 17 whereas 824B corresponds to 100CrMo7 in the same standard. The discontinued Swedish standard for 802F is 2258. In SS-EN ISO 683 - 17, the soft-annealed execution is designated by the addendum “+A” after the steel name.
Tempering at 150-250°C after hardening in oil results in a hardness of 60-62 HRC which is suitable for bearings and other applications where high hardness is needed. If better impact toughness is required, the tempering temperature can be increased to >350°C. Another heat-treatment alternative to achieve high hardness is austempering in a salt bath at 200 - 250°C. A combination of hard, wear-resistant surface and tougher core can be accomplished through induction hardening.
802F and 824B are not weldable.