For injection molds there are several steel types available. For long production runs a durable mold is required. The cost of tool steel is often not more than 10% of total mold cost. Important steel properties are:
- Ease of machining
- Dimensional stability after heat treatment
- Wear resistance
- Surface finish
- Corrosion resistance
Use of specific alloying elements like carbon may increase single properties, however, often at the cost of other properties. The table below shows some popular grades of mold tool steel.
Corrosion resistant hardened steels should be selected when conventional flame retardants are used. In the case of halogen free flame retardant DSM thermoplastics, standard steel types can be selected.
Beryllium copper inserts may be used for improved cooling near hot spots. High heat conductivity is also required for gate drops in hot runner molds.
Standardization of mold parts is growing, not only for ejector pins, leader pins and bushings, but also for mold plates and even complete mold bases. These standard mold bases require only machining of the cores, cavities and cooling channels and fitting of an ejection system. Advantages are:
- Cost savings (30-50%)
- Short delivery times
- Easy and rapid repair
Steel types for injection molds.