No, higher hardness is not always better for the steel used in injection molds. Hardness is a key factor in selecting mold steel, but it must be balanced with other properties such as toughness, wear resistance, and corrosion resistance. Selecting the optimal hardness is based on a comprehensive consideration of product requirements, plastic material, production volume, and cost.
Excellent Wear Resistance: High hardness directly provides stronger resistance to wear. This is crucial in the following situations:
For plastics with reinforcing fibers, such as engineering plastics with added glass fiber.These fibers act like files, rapidly wearing down the mold cavity surface.
For high-volume production molds requiring hundreds of thousands or even millions of cycles, high hardness ensures dimensional stability over long-term use, preventing product flash or dimensional inaccuracies caused by wear.
Good Resistance to Deformation: High-hardness molds are less prone to elastic deformation under high injection pressure (especially in large molds), better maintaining the original shape and dimensional accuracy of the cavity.
Disadvantages and Risks of High Hardness:
Reduced Toughness, Increased Brittleness: This is the primary issue associated with high hardness. Molds are subjected to various stresses during production and handling, including:
Impact stress from moving components like ejector pins, sliders, and angle lifts.
Thermal stress from the cyclic heating and cooling during injection.
Assembly stress from excessive preload during mold assembly.
Steel with poor toughness is more susceptible to cracking or chipping under these stresses, particularly in areas with thin walls, sharp corners, or other stress concentrations.
Increased Machining Difficulty and Cost:
Difficult Cutting: Higher hardness leads to greater tool and electrode wear for machining equipment (CNC, EDM, etc.), resulting in longer processing times and significantly higher costs.
Difficult Repair: When issues arise during use, high-hardness steel is more challenging to weld, polish, or perform other maintenance on.
Increased Susceptibility to Thermal Fatigue: While hard, some high-hardness steels may not offer the best thermal fatigue resistance. Under rapid cycling conditions, they might be more prone to surface heat checking.
ATC-Mould has a strong mold design team and extensive injection molding production experience, providing valuable expertise in actual injection mold manufacturing and plastic product production. By carefully selecting subtle differences in steel materials, we can enhance the service life of easily damaged inserts and slider inserts, improving production smoothness. In practice, we often choose 1.2767 steel for angle lifts and slider inserts. This material has a lower quenched hardness compared to 1.2379 / 1.2344, but offers better