The best steel for plastic injection mold tooling

Engineers have a plenty of things to consider when working on a plastic injection mold for a project. While there are many thermoforming resins to choose from, a decision also must be made about the best steel to use for the injection molding tool.

The type of steel selected for the tool affects production lead time, cycle time, finished part quality and cost. This article lists the top two steels for tooling; we weigh the pros and cons of each one to help you decide which is best for your next plastic injection molding project.



An air-hardened tool steel, H13 is considered a hot work steel and is a great choice for large-volume production orders with continuous heating and cooling cycles.

Pro: H13 can hold close dimensional tolerances after more than one million uses, and it’s also easy to machine prior to heat treatment when the metal is relatively soft. Another positive is that it can be polished to a mirror finish for clear or optical parts.

Con: H13 has average heat transference but still doesn’t stand up to aluminum in the heat-transfer category. Additionally, it will be more expensive than aluminum or P20.


P20 is the most widely used plastic mould steel, good for volumes up to 50,000. It’s known for its reliability for general-purpose resins and abrasive resins with glass fibers.

Pro: P20 is used by many engineers and product designers because it’s more cost effective and tougher than aluminum in some applications. It can withstand higher injection and clamping pressures, which are found on larger parts representing bigger shot weights. Additionally, P20 machines well and can be repaired via welding.

Con: P20 is less resistant to chemically corrosive resins like PVC.

There are several options for designers and engineers to consider for their next plastic injection molding project. With the right manufacturing partner, choosing the right material will help meet project goals, expectations and deadlines.

Shanghai Histar Metal

Post time: Apr-19-2021