In mold manufacturing, material selection is often decided long before machining begins. From our experience, many issues related to mold accuracy, polishing quality, or service life are not caused by processing errors, but by material choices made at the very early design stage. At XP MOLD, we work closely with moldmaking and injection molding companies on high-precision mold components. This article summarizes practical insights from real projects, focusing on how to select suitable mold steels—and how to avoid common mistakes that often lead to costly rework later.
It is pre-hardened at the factory, with a hardness of 30–35 HRC. It can be processed directly without further heat treatment, has good machinability, and is not prone to chipping.
In XP MOLD projects, P20 is mostly used for:
Ordinary plastics such as ABS and PP
Daily necessities and home appliance casings
Small to medium-volume molds
With normal use, a mold life of 100,000 to 300,000 cycles is achievable.
Points to note:
P20 steel is not corrosion-resistant and is not suitable for materials with high glass fiber content. Using it with PVC or GF plastics can easily lead to severe wear and tear over time. If you must use it, at least consider surface treatment, such as chrome plating.
718H can be understood as a "more stable P20."
It generally has a hardness of 35–40 HRC, a more uniform material structure, significantly better polishing results, and higher dimensional stability.
Common applications include:
PEEK, LCP
High glass fiber–reinforced materials
Automotive engine components and 5G antenna housings
When mold design and processing are properly controlled, service life can exceed 1 million cycles in real production environments.
Industry trend:
Looking ahead to 2025, low-carbon H13 is being adopted more widely. It helps reduce overall energy consumption by around 30% while maintaining the same performance level, making it particularly suitable for long-term, high-volume production programs.
When surface appearance is critical—especially for transparent or high-gloss parts—NAK80 is often the first material considered.
Its main advantages include:
No heat treatment required, with hardness around 40–42 HRC
Very consistent polishing behavior
Excellent mirror-finish capability, with Ra values reaching approximately 0.01 μm
Typical applications:
PC and PMMA products
Cosmetic packaging molds
With proper machining and maintenance, mold life of 500,000 to 1,000,000 cycles is commonly achieved.
Cautionary notes:
NAK80 is sensitive to environmental conditions and auxiliary materials. Release agents containing sulfur or chlorine should be avoided. In humid environments, rust prevention measures are essential, as surface quality can degrade quickly if neglected.
For high-temperature molding applications, H13 remains a standard choice.
After heat treatment, it typically reaches 48–52 HRC and performs reliably under continuous temperatures of 500–600°C, with strong resistance to thermal fatigue.
Common applications include:
PEEK and LCP materials
High glass fiber reinforced plastics
Automotive engine-related components and 5G antenna housings
With proper design and processing, mold life can exceed 1 million cycles.
Industry trend:
By 2025, low-carbon H13 variants are increasingly adopted. These materials can reduce overall energy consumption by approximately 30% while maintaining performance
S136 is well known for its corrosion resistance.
With a chromium content of approximately 13.6%, it performs reliably in corrosive environments while still offering good polishing characteristics.
Typical applications include:
PVC and other corrosive plastics
Medical disposable products
Food-grade packaging molds
After heat treatment, hardness usually falls within 48–52 HRC, and mold life commonly ranges from 500,000 to 800,000 cycles, depending on application conditions.
Special note:
For medical-related projects, material traceability and processing procedures often need to comply with standards such as ISO 13485. These requirements should be taken into account at the material selection stage, not addressed later as a corrective measure.
Over the past two years, several changes have become more noticeable across the industry:
Wider adoption of low-carbon mold steel
Increased use of nano-coatings in high-wear areas
AI-assisted tools used to shorten material selection and development cycles
That said, no matter how technology develops, the underlying principle remains the same:
the material must fit the product and the application.
First, avoid relying purely on past experience.
Once glass fiber content exceeds 30%, using standard mold steel becomes a high-risk choice. Similarly, selecting P20 for transparent parts almost always leads to polishing issues later in the project.
Second, avoid extreme decisions—either over-specifying or cutting corners.
There is little benefit in using premium steel for basic household appliance molds. On the other hand, choosing low-grade materials such as 45# steel for high-end molds purely to reduce cost often leads to higher expenses over the mold’s lifecycle.
Third, never underestimate compliance requirements.
Industries such as medical and automotive manufacturing follow strict standards for both materials and processes. If these requirements are overlooked during the material selection phase, correcting them later can be extremely difficult.
Choosing the right mold steel is rarely a decision based on a single factor. It requires balancing product requirements, processing stability, expected production volume, and long-term reliability.
At XP MOLD, material selection is always discussed with our customers at an early stage, based on actual drawings and real application conditions—not assumptions.
If you are working on a connector mold or another precision mold project and would like to review material options before machining begins, you are welcome to contact.
