Meaning
Martensitic stainless steel provides a combination of high hardness and corrosion resistance for injection moulding applications. Heat treatment allows 420 stainless steel to achieve the high lustre required for optical components or medical housings. Chromium content in the alloy resists oxidation caused by humid environments or contaminated cooling water.
Alloy Composition
High carbon content within the metallic matrix allows the material to reach fifty Rockwell C after standard heat treatment cycles. This hardness prevents the deformation of delicate shut-off surfaces under clamping pressure.
Corrosion Resistance
Protection against chemical attack is a primary function of the chromium levels found in 420 stainless steel. While virgin resins are stable, regrind material sometimes releases acidic gases that degrade non-stainless tool steels. Using this alloy reduces the need for protective plating on the cavity surfaces.
The metal remains stable even when exposed to the corrosive byproducts of flame-retardant additives.
Polishing Performance
A fine and uniform grain structure supports the attainment of a diamond-buffed finish on the mould face. Because the material is exceptionally clean, 420 stainless steel avoids the pitting that occurs in lower quality steels during the final polishing stages. This property ensures that moulded parts exhibit high clarity and no surface defects.
Smooth surfaces also assist in the ejection of the part by reducing the friction between the plastic and the steel. Proper polishing reduces the risk of microscopic cracks forming on the tool surface during high-pressure cycles.
