2090/56SiCr7 is a low-alloy silicon spring steel. The carbon content is about 0.55% and the bars in stock are controlled cooled after hot rolling such that the as-rolled hardness is kept low in order to facilitate machining and/or cold forming. The hardenability of silicon spring steels is generally lower than for grades based upon chrome, such as 51CrV4 (SS 2230), so that heat treatment to attain sufficiently high strength and hardness is only feasible for smaller sizes. However, in suitable dimensions, the material can attain very high levels of strength and hardness via quenching and tempering such that it might be considered for other applications apart from springs.
The flat bars in stock have rounded edges and the execution is as-hot-rolled. As regards chemical analysis, the steel conforms fully to the requirements for grade 56SiCr7 in SS-EN 10089. The discontinued Swedish standard for this grade is 2090. In SS-EN 10089, the as-hot-rolled execution is designated by the addendum “+AR” after the steel name.
Tempering at 450-500°C after hardening in oil results in a hardness of 44-48 HRC which is the normal level for spring applications. If higher hardness is needed, tempering can be done at a lower temperature, 200 - 250°C.
Welding of 2090/56SiCr7 is not to be recommended.