Tool Steel Selection Guidelines for High Volume Injection Moulding Tooling Baseline Fabrication
High-volume injection moulding baseline tooling demands martensitic stainless or pre-hardened steels matched to polymer abrasiveness and cycle volume.
Electro-Slag Remelting
Meaning
Secondary refining processes for high-purity steels remove non-metallic inclusions and chemical segregation to enhance structural uniformity. Utilising electro-slag remelting produces mould steels with superior mechanical properties and exceptional polishability. This process is essential for producing high-finish plastic parts, where any steel imperfection would result in surface defects.
Process Mechanism
Solidified steel ingots are consumed as electrodes and melted through a pool of molten, electrically conductive slag. During electro-slag remelting, droplets of the metal fall through the reactive slag layer, which extracts sulphur and other impurities. This continuous cleaning creates a highly homogeneous ingot with minimal chemical variation from the bottom to the top.
The progressive solidification that follows eliminates axial porosity, yielding a metal structure that can withstand high pressure during heavy moulding cycles.
Mould Polishability
Lenses and other high-clarity plastic components require mould cavities with mirror-like finishes. Steels processed by electro-slag remelting possess the cleanliness needed to achieve these surfaces without pitting or orange-peel effects. The absence of hard oxide inclusions ensures that polishing tools can work the steel uniformly across the entire cavity.
Tooling Endurance
Extreme heat during high-speed moulding cycles can induce thermal fatigue and cracking in standard tool steels. Incorporating steel refined via electro-slag remelting increases the resistance of the mold to heat checking. This durability reduces maintenance downtime and prevents costly tool rebuilds during high-volume programs.