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Rundstål 825B/803F

Ovako 803F and 825B are low-alloy bearing steels with about 1% carbon. 803F is alloyed with chrome while 825B is somewhat higher alloyed and contains molybdenum in addition to chrome. As stocked, the bars 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 bars stocked are in grade 803F up to diameter 55 mm. Larger dimensions are in the higher-alloyed grade 825B. The surface execution is peeled up to 100 mm and hot-rolled for larger diameters.

As regards chemical analysis, 803F conforms fully to the requirements for grade 100Cr6 in

SS-EN ISO 683 - 17 whereas 825B corresponds to 100CrMo7-3 in the same standard. The discontinued Swedish standard for 803F 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.

803F and 825B are not weldable.

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