Meaning
Martensitic chromium steel alloy designed for high polish retention and corrosion resistance operates as a core material for high cavitation injection moulds. This alloy contains approximately sixteen percent chromium alongside carbon additions that promote hardening during thermal treatment. S136 stainless steel governs tool longevity against aggressive fluorinated and chlorinated thermoplastic resins during high pressure compression cycles.
The application boundary sits where abrasive mineral fillers demand specialized powder metallurgy grades rather than conventional wrought alloy plates.
Cavity Performance
High pressure injection moulding demands absolute dimensional stability across extended production runs without micro pitting on critical runner surfaces. S136 stainless steel provides the high density matrix necessary to resist compressive fatigue under clamping loads exceeding hundreds of tonnes. Thermal conductivity parameters dictate cooling channel placement within the block to prevent localized hot spots during rapid cycling.
Toolmakers machine the alloy in a soft annealed state prior to vacuum hardening processes that lock in final microstructural integrity. Premature cavity wear results directly from improper thermal tempering protocols that leave retained austenite inside the crystalline lattice.
Corrosion Resistance
Polymeric degradation byproducts generate acidic residues that attack standard tool steels during prolonged machine stoppages in humid environments. S136 stainless steel prevents pitting corrosion through a passive chromium oxide film that reforms instantly upon oxygen exposure after mechanical polishing. Polishing technicians bring these tool faces to a mirror finish to eliminate microscopic undercuts where polymer melt stagnation initiates localized chemical attack.
Surface passivation treatments augment this chemical resistance without altering bulk mechanical properties or dimensional tolerances of the core insert. Moulders processing flame retarded engineering resins rely on this grade to eliminate downtime caused by rust bleeding through parting lines.
Economic Boundary
Virgin resin economics rely on predictable cycle times governed by optimal heat transfer coefficients within the mould assembly. S136 stainless steel commands a substantial raw material premium over carbon tool steels, yet eliminates the recurring expense of frequent cavity re-plating. Regrind polymer streams containing higher contamination levels accelerate abrasive wear along gate locations unless the surrounding steel possesses sufficient hardness.
Tooling budgets balance initial material acquisition expenses against projected lifetime part volumes before finalizing steel selection for production cavities. Proper maintenance schedules ensure this alloy delivers consistent surface reproduction across millions of injection cycles without catastrophic failure.
