16NiCrS4 is a low-alloy (chrome-nickel) case-hardening steel which is M-treated with calcium for improved machinability. Furthermore, machining of parts with complex shape, e.g. gear wheels, is facilitated even further through the steel being soft-annealed after rolling to guarantee a hardness of 217 HB or below.
16NiCrS4 is standardised in SS-EN ISO 683 - 3. The hardness as supplied corresponds to “+A” (soft annealed). The (discontinued) SS-designation is 2511.
Base hardenability is an important characteristic of case-hardening steels since it determines core properties after hardening and tempering. It is normally specified in terms of a Jominy diagram, which gives the hardness distribution as determined on a sample which has been hardened by directing a spray of water at its one end according to a standardised procedure. The addendum “+HL” after the steel name signifies that the analysis is controlled such that the Jominy curve lies between limits which are stipulated in the SS-EN ISO 683 - 3 standard.
In Tibnor’s stock-standard programme for 16NiCrS4, diameters >20 mm are peeled whereas those 10-20 mm are cold drawn. In the latter execution, the relevant standard for 16NiCrS4 is
SS-EN 10277 - 4 with conditions “+C” (cold-drawn) and “+A” (soft-annealed). The cold-drawn diameter tolerance is h10 (ISO 286-2).
The low carbon content of 16NiCrS4 means that weldability is quite good but even so, pre-heating will normally be required unless the parts are very small. Thanks to the low hardness and soft-annealed microstructure, machinability is excellent.