P20+S is a sulfurized, pre-hardened plastic injection mold steel — a distinctly different category from the cutting-tool and die steels covered elsewhere in this library. The base P20 chemistry (a Cr-Mn-Mo low-alloy steel) is already a mold-steel workhorse, supplied pre-hardened to roughly 28-32 HRC so moldmakers can machine cavities and cores directly without a separate hardening cycle. The "+S" designation means the steel has a controlled sulfur addition, typically 0.05-0.10%, deliberately built into the chemistry to form manganese sulfide inclusions throughout the matrix.

Those sulfide inclusions act as internal chip-breakers and lubricant pockets during cutting, which is the entire point of the "+S" variant: it machines noticeably easier than plain P20, with shorter chips, lower cutting forces, and better surface finish, at the cost of a modest reduction in polishability and weldability. That trade-off is generally accepted in mold work because most P20+S tooling doesn't need mirror-polish optical surfaces the way plain P20 or P20+Ni sometimes does. Typical applications are injection mold cavities, cores, and mold bases for plastics processing where machining time and tool wear matter more than final surface polish.

The old page's DIN designation was missing its hyphen ("40CrMnMoS86"); the correct formatting is 40CrMnMoS8-6.

This composition was intact and internally consistent on the old page and required no correction — note the deliberate sulfur addition (0.05-0.10%) that distinguishes this grade from standard, non-sulfurized P20.

P20+S is one of the more forgiving materials in this library to machine, precisely because the sulfur addition was engineered for that purpose. In the pre-hardened, as-delivered condition (28-32 HRC), the manganese sulfide inclusions break chips short and act as a solid-state lubricant at the tool-chip interface, reducing built-up edge formation and cutting forces compared to plain P20 at the same hardness. Surface finish is typically better and more consistent than on non-sulfurized mold steels machined at similar parameters.

Because the material arrives pre-hardened, there's no post-machining heat-treatment distortion to plan around — mold cavities and cores are cut directly to final or near-final dimension. Coated carbide grades handle P20+S comfortably at moderate-to-aggressive speeds; the main practical limitation is not tool wear but achieving the surface finish and dimensional accuracy the mold cavity requires, since the sulfide inclusions that ease cutting are also the reason P20+S takes a duller polish than plain P20.

The turning range reflects published shop practice for pre-hardened P20+S with coated carbide (roughly 80 m/min for conservative roughing up to 150 m/min for light finishing); other operations are scaled proportionally. Always verify with a test cut.

Turning

Parting / Grooving

Milling

The old page mislabeled this section "...for Steel 1006" — an unrelated low-carbon steel copy-paste error. The values themselves match this site's standard steel-machining geometry and are correctly applied here.