Meaning
Hardened tool steel components placed within mold bases provide the wear resistance needed for high-volume injection molding of abrasive resins. This chromium-hot-work steel is selected for its high toughness and thermal fatigue resistance, allowing it to withstand repeated heating and cooling cycles without cracking. These components form the actual shape of the molded part, bearing the direct force and heat of the incoming molten plastic.
Steel Performance
Heat treatment processes harden this alloy to a typical range of forty-eight to fifty-two Rockwell C, balancing wear resistance with impact strength. When h13 cavity inserts are used in a mold, they resist the erosive action of glass-filled polymers and flame-retardant additives. This durability maintains the critical dimensions of the molded parts across millions of cycles, reducing the frequency of tooling maintenance.
Correct cooling line placement within these steel blocks is essential to ensure uniform heat extraction and prevent localized part warpage.
Surface Treatment
Polishing and coating options further extend the operational life of the steel inserts. Chemical vapor deposition or nitriding treatments can be applied to the steel surfaces to increase surface hardness and improve release properties. These surface treatments reduce frictional heat during the injection phase and assist in ejecting complex geometries without scuffing the plastic walls.
Maintenance Factor
Regular inspection for thermal checking or gate erosion prevents surface defects on the molded components. Small cracks in the insert steel will transfer to the plastic, appearing as raised lines or flash on the finished parts. Replacing or refurbishing worn inserts restores the tool to its original specifications without needing to replace the entire mold base.
